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Transcript of Core Java
Sun
Java™ Programmi
Ja guage
Services
ng Language
va™ Programming Lan
SL-275
Copyrig
This pro lation. No part of this product or document maybe repro
Third-p
Sun, Sun emarks of Sun Microsystems, Inc. in the U.S. andother co
UNIX is
Netscap
The OPE es the pioneering efforts of Xerox in researchingand dev ox to the Xerox Graphical User Interface, whichlicense a
U.S. Gov
RESTRI nd FAR 52.227-19(6/87), or DFAR 252.227-7015(b)(6/95
DOCUM IES, INCLUDING ANY IMPLIED WARRANTYOF MER HE EXTENT THAT SUCH DISCLAIMERS AREHELD T
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ht 2006 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, California 95054, U.S.A. All rights reserved.
duct or document is protected by copyright and distributed under licenses restricting its use, copying, distribution, and decompiduced in any form by any means without prior written authorization of Sun and its licensors, if any.
arty software, including font technology, is copyrighted and licensed from Sun suppliers.
Microsystems, the Sun Logo, Java, JavaBeans, JavaOS, JDBC, JDK, JVM, J2SE, Jini, and Solaris are trademarks or registered traduntries.
a registered trademark in the U.S. and other countries, exclusively licensed through X/Open Company, Ltd.
e Navigator is a trademark of Netscape Communications Corporation.
N LOOK and Sun Graphical User Interface was developed by Sun Microsystems, Inc. for its users and licensees. Sun acknowledgeloping the concept of visual or graphical user interfaces for the computer industry. Sun holds a non-exclusive license from Xerlso covers Sun’s licensees who implement OPEN LOOK GUIs and otherwise comply with Sun’s written license agreements.
ernment approval might be required when exporting the product.
CTED RIGHTS: Use, duplication, or disclosure by the U.S. Government is subject to restrictions of FAR 52.227-14(g)(2)(6/87) a) and DFAR 227.7202-3(a).
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ommodity Classification Number Assigned: 2 February 2002
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Ce prod ution, et la décompilation. Aucune partie de ceproduit e Sun et de ses bailleurs de licence, s’il y en a.
Le logic é par des fournisseurs de Sun.
Sun, Sun es marques déposées de Sun Microsystems, Inc.aux Etat
UNIX es
Netscap
L’interfa . Sun reconnaît les efforts de pionniers de Xeroxpour lar n détient une licence non exclusive de Xerox surl’interfa tion graphique OPEN LOOK et qui en outre seconform
L’accord
LA DOC ESSES OU TACITES SONT FORMELLEMENTEXCLU RELATIVE A LA QUALITE MARCHANDE, AL’APTIT
ht 2006 Sun Microsystems Inc., 4150 Network Circle, Santa Clara, California 95054, Etats-Unis. Tous droits réservés.
uit ou document est protégé par un copyright et distribué avec des licences qui en restreignent l’utilisation, la copie, la distribou document ne peut être reproduite sous aucune forme, par quelque moyen que ce soit, sans l’autorisation préalable et écrite d
iel détenu par des tiers, et qui comprend la technologie relative aux polices de caractères, est protégé par un copyright et licenci
Microsystems, the Sun Logo, Java, JavaBeans, JavaOS, JDBC, JDK, JVM, J2SE, Jini, et Solaris sont des marques de fabrique ou ds-Unis et dans d’autres pays.
t une marques déposée aux Etats-Unis et dans d’autres pays et licenciée exclusivement par X/Open Company, Ltd.
e Navigator est une marque de Netscape Communications Corporation aux Etats-Unis et dans d’autres pays.
ces d’utilisation graphique OPEN LOOK et Sun™ a été développée par Sun Microsystems, Inc. pour ses utilisateurs et licenciésecherche et le développement du concept des interfaces d’utilisation visuelle ou graphique pour l’industrie de l’informatique. Suce d’utilisation graphique Xerox, cette licence couvrant également les licenciés de Sun qui mettent en place l’interface d’utilisaent aux licences écrites de Sun.
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UMENTATION EST FOURNIE “EN L’ETAT” ET TOUTES AUTRES CONDITIONS, DECLARATIONS ET GARANTIES EXPRES, DANS LA MESURE AUTORISEE PAR LA LOI APPLICABLE, Y COMPRIS NOTAMMENT TOUTE GARANTIE IMPLICITEUDE A UNE UTILISATION PARTICULIERE OU A L’ABSENCE DE CONTREFAÇON.
Java™ Programmi iv2006 Sun Microsystem
....................... Preface-xvi
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..................................Preface-xxiv....................................Preface-xxv
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ng Languages, Inc. All Rights Reserved. Sun Services, Revision F.1
Course Contents
About This Course ..............................................................Course Goals ..........................................................................................Course Overview ..................................................................................Course Map ............................................................................................Topics Not Covered ..............................................................................How Prepared Are You? ......................................................................Introductions .........................................................................................How to Use the Icons ............................................................................Typographical Conventions and Symbols .......................................
Getting Started ....................................................................Objectives ...............................................................................................Relevance ................................................................................................What Is the Java™ Technology? .........................................................Primary Goals of the Java Technology ..............................................The Java Virtual Machine ....................................................................Garbage Collection ...............................................................................The Java Runtime Environment ..........................................................Operation of the JRE With a Just-In-Time (JIT) Compiler ..............JVM™ Tasks ..........................................................................................The Class Loader ...................................................................................The Bytecode Verifier ...........................................................................A Simple Java Application ...................................................................The TestGreeting Application .........................................................The Greeting Class ..............................................................................Compiling and Running the TestGreeting Program ....................
Java™ vCopyrig
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Compile-Time Errors ............................................................................Runtime Errors ......................................................................................Java Technology Runtime Environment ...........................................
Object-Oriented Programming ...........................................Objectives ...............................................................................................Relevance ................................................................................................Software Engineering ...........................................................................The Analysis and Design Phase ..........................................................Abstraction .............................................................................................Classes as Blueprints for Objects ........................................................Declaring Java Technology Classes ....................................................Declaring Attributes .............................................................................Declaring Methods ................................................................................Accessing Object Members ..................................................................Information Hiding ...............................................................................Encapsulation ........................................................................................Declaring Constructors ........................................................................The Default Constructor ......................................................................Source File Layout ................................................................................Software Packages ................................................................................The package Statement ........................................................................The import Statement ..........................................................................Directory Layout and Packages ..........................................................Development .........................................................................................Compiling Using the -d Option .........................................................Terminology Recap ...............................................................................Using the Java Technology API Documentation ..............................Java Technology API Documentation With HTML3 .......................
Java™ viCopyrig
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Identifiers, Keywords, and Types ......................................Objectives ...............................................................................................Relevance ................................................................................................Comments ..............................................................................................Semicolons, Blocks, and White Space ...............................................Identifiers ...............................................................................................Java Programming Language Keywords ..........................................Primitive Types .....................................................................................Logical – boolean .................................................................................Textual – char .......................................................................................Textual – String ...................................................................................Integral – byte, short, int, and long ...............................................Floating Point – float and double ....................................................Variables, Declarations, and Assignments ........................................Java Reference Types ............................................................................Constructing and Initializing Objects ................................................Memory Allocation and Layout ..........................................................Explicit Attribute Initialization ...........................................................Executing the Constructor ...................................................................Assigning a Variable .............................................................................Assigning References ............................................................................Pass-by-Value ........................................................................................The this Reference ...............................................................................Java Programming Language Coding Conventions ........................
Expressions and Flow Control ..........................................Objectives ...............................................................................................Relevance ................................................................................................Variables and Scope ..............................................................................Variable Scope Example .......................................................................
Java™ viiCopyrig
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Variable Initialization ...........................................................................Initialization Before Use Principle ......................................................Operator Precedence ............................................................................Logical Operators ..................................................................................Bitwise Logical Operators ....................................................................Right-Shift Operators >> and >>> .......................................................Left-Shift Operator << ..........................................................................Shift Operator Examples ......................................................................String Concatenation With + ...............................................................Casting ....................................................................................................Promotion and Casting of Expressions .............................................Simple if, else Statements ..............................................................Complex if, else Statements ..........................................................Switch Statements .................................................................................Looping Statements ..............................................................................Special Loop Flow Control ..................................................................The break Statement ............................................................................The continue Statement .....................................................................Using break Statements with Labels .................................................Using continue Statements with Labels ..........................................
Arrays ...................................................................................Objectives ...............................................................................................Relevance ................................................................................................Declaring Arrays ...................................................................................Creating Arrays .....................................................................................Creating Reference Arrays ...................................................................Initializing Arrays .................................................................................Multidimensional Arrays .....................................................................Array Bounds ........................................................................................
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Using the Enhanced for Loop ............................................................Array Resizing .......................................................................................Copying Arrays .....................................................................................
Class Design ........................................................................Objectives ...............................................................................................Relevance ................................................................................................Subclassing .............................................................................................Single Inheritance ..................................................................................Access Control .......................................................................................Overriding Methods .............................................................................Overridden Methods Cannot Be Less Accessible .............................Invoking Overridden Methods ...........................................................Polymorphism .......................................................................................Virtual Method Invocation ..................................................................Heterogeneous Collections ..................................................................Polymorphic Arguments .....................................................................The instanceof Operator ...................................................................Casting Objects ......................................................................................Overloading Methods ..........................................................................Methods Using Variable Arguments .................................................Overloading Constructors ...................................................................Constructors Are Not Inherited ..........................................................Invoking Parent Class Constructors ...................................................Constructing and Initializing Objects: A Slight Reprise ..................Constructor and Initialization Examples ...........................................The Object Class ..................................................................................The equals Method ..............................................................................An equals Example .............................................................................The toString Method .........................................................................
Java™ ixCopyrig
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Wrapper Classes ...................................................................................Autoboxing of Primitive Types ...........................................................
Advanced Class Features ..................................................Objectives ...............................................................................................Relevance ................................................................................................The static Keyword ...........................................................................Class Attributes .....................................................................................Class Methods .......................................................................................Static Initializers ....................................................................................The final Keyword .............................................................................Final Variables .......................................................................................Blank Final Variables ............................................................................Old-Style Enumerated Type Idiom ....................................................The New Enumerated Type ................................................................Advanced Enumerated Types .............................................................Static Imports .........................................................................................Abstract Classes ....................................................................................The Solution ...........................................................................................Interfaces ................................................................................................The Flyer Example ................................................................................Multiple Interface Example .................................................................Uses of Interfaces ..................................................................................
Exceptions and Assertions ................................................Objectives ...............................................................................................Relevance ................................................................................................Exceptions and Assertions ..................................................................Exceptions ..............................................................................................Exception Example ...............................................................................
Java™ xCopyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The try-catch Statement ...................................................................Call Stack Mechanism ..........................................................................The finally Clause .............................................................................Exception Categories ............................................................................Common Exceptions .............................................................................The Handle or Declare Rule ................................................................Method Overriding and Exceptions ...................................................Creating Your Own Exceptions ..........................................................Handling a User-Defined Exception ..................................................Assertions ...............................................................................................Recommended Uses of Assertions .....................................................Internal Invariants .................................................................................Control Flow Invariants .......................................................................Postconditions and Class Invariants .................................................Controlling Runtime Evaluation of Assertions ................................
Text-Based Applications ....................................................Objectives ...............................................................................................Relevance ................................................................................................Command-Line Arguments ................................................................System Properties ..................................................................................The Properties Class .........................................................................Console I/O ...........................................................................................Writing to Standard Output ................................................................Reading From Standard Input ............................................................Simple Formatted Output ....................................................................Simple Formatted Input .......................................................................Files and File I/O ..................................................................................Creating a New File Object ...............................................................The File Tests and Utilities ................................................................
Java™ xiCopyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
File Stream I/O ......................................................................................File Output Example .............................................................................The Collections API ..............................................................................A Set Example ......................................................................................A List Example ....................................................................................Collections in JDK™ Version 1.1 .......................................................Generics ..................................................................................................Generic Collections API .......................................................................Compiler Warnings .............................................................................Iterators ...................................................................................................The Iterator Interface Hierarchy .........................................................Enhanced for Loop ..............................................................................
Building Java GUIs .............................................................Objectives ...............................................................................................Relevance ................................................................................................Abstract Window Toolkit ....................................................................The java.awt Package .........................................................................Containers ..............................................................................................Positioning Components ......................................................................Frames .....................................................................................................The FrameExample Class .....................................................................Example Frame ......................................................................................Panels ......................................................................................................The FrameWithPanel Class .................................................................Layout Managers ..................................................................................Default Layout Managers ....................................................................A Simple FlowLayout Example ..........................................................The FlowLayout Manager ...................................................................The FlowExample Class .......................................................................
Java™ xiiCopyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The BorderLayout Manager ...............................................................Organization of the Border Layout Components .............................The BorderExample Class ...................................................................Example of BorderLayout ..................................................................The GridLayout Manager ...................................................................The GridExample Class .......................................................................Example of GridLayout .....................................................................The ComplexLayoutExample Class ..................................................Drawing in AWT ..................................................................................Various Shapes Drawn by the Graphics Object ..............................
GUI Event Handling .............................................................Objectives ...............................................................................................Relevance ................................................................................................What Is an Event? .................................................................................Delegation Model ..................................................................................A Listener Example ...............................................................................Event Categories ...................................................................................Method Categories and Interfaces ......................................................Complex Example .................................................................................Multiple Listeners .................................................................................Event Adapters ......................................................................................Event Handling Using Inner Classes ................................................Event Handling Using Anonymous Classes ....................................
GUI-Based Applications .....................................................Objectives ...............................................................................................Relevance ................................................................................................AWT Components ................................................................................AWT Listeners .......................................................................................
Java™ xiiiCopyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
How to Create a Menu .........................................................................Creating a MenuBar ...............................................................................Creating a Menu .....................................................................................Creating a MenuItem .............................................................................Creating a CheckBoxMenuItem ...........................................................Controlling Visual Aspects ..................................................................J.F.C./Swing Technology .....................................................................
Threads ................................................................................Objectives ...............................................................................................Relevance ................................................................................................Threads ...................................................................................................Creating the Thread ..............................................................................Starting the Thread ...............................................................................Thread Scheduling ................................................................................Thread Scheduling Example ...............................................................Terminating a Thread ...........................................................................Basic Control of Threads ......................................................................The join Method ..................................................................................Other Ways to Create Threads ............................................................Selecting a Way to Create Threads .....................................................Using the synchronized Keyword ...................................................The Object Lock Flag ............................................................................Releasing the Lock Flag ........................................................................Using synchronized – Putting It Together ......................................Thread State Diagram With Synchronization ...................................Deadlock .................................................................................................Thread Interaction – wait and notify ..............................................Thread Interaction .................................................................................Thread State Diagram With wait and notify ................................
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Monitor Model for Synchronization ..................................................The Producer Class ..............................................................................The Consumer Class ..............................................................................The SyncStack Class ............................................................................The pop Method ....................................................................................The push Method ..................................................................................The SyncTest Class ..............................................................................The SyncTest Class ..............................................................................
Advanced I/O Streams ........................................................Objectives ...............................................................................................Relevance ................................................................................................I/O Fundamentals ................................................................................Fundamental Stream Classes ..............................................................Data Within Streams .............................................................................The InputStream Methods .................................................................The OutputStream Methods ...............................................................The Reader Methods ............................................................................The Writer Methods ............................................................................Node Streams .........................................................................................A Simple Example .................................................................................Buffered Streams ...................................................................................I/O Stream Chaining ...........................................................................Processing Streams ...............................................................................The InputStream Class Hierarchy ....................................................The OutputStream Class Hierarchy ..................................................The Reader Class Hierarchy ...............................................................The Writer Class Hierarchy ...............................................................
Java™ xvCopyrig
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Networking ...........................................................................Objectives ...............................................................................................Relevance ................................................................................................Networking ............................................................................................Networking With Java Technology ....................................................Java Networking Model .......................................................................Minimal TCP/IP Server .......................................................................Minimal TCP/IP Client ........................................................................
Sun
Java™ Programmi
Services
ng Language
Preface
About This Course
Java™ Preface, slide xvii of xxviiCopyrig
Th d skills to:
hat leverage theuage, such asrphismrom the
ressionsructs
sing exception
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Course Goals
is course provides you with knowledge an
• Create Java™ technology applications tobject-oriented features of the Java langencapsulation, inheritance, and polymo
• Execute a Java technology application fcommand-line
• Use Java technology data types and exp• Use Java technology flow control const• Use arrays and other data collections• Implement error-handling techniques u
handling
Java™ Preface, slide xviii of xxviiCopyrig
nterface (GUI)ents: panels,s
nality to read
rotocol/ommunicates
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Course Goals
• Create an event-driven graphical user iby using Java technology GUI componbuttons, labels, text fields, and text area
• Implement input/output (I/O) functiofrom and write to data and text files
• Create multithreaded programs• Create a simple Transmission Control P
Internet Protocol (TCP/IP) client that cthrough sockets
Java™ Preface, slide xix of xxviiCopyrig
Th
nguage to the Java
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Course Overview
is course describes the following areas:
• The syntax of the Java programming la• Object-oriented concepts as they apply
programming language• GUI programming• Multithreading• Networking
Sun Services
Course Map
The Java Programming Language Basics
More Object-Oriented Programming
Building Applications
Developing Graphical User Interfaces
Advanced Java Programming
Getting StartedObject-Oriented
Programming
Identifiers,Keywords, and
Types
Arrays
Class DesignAdvanced
Class Features
Text-Based
Applications
Building Java
GUIs
GUI Event
Handling
GUI-Based
Applications
Advanced
I/O StreamsThreads Networking
Expressions
and Flow Control
Exceptions
and Assertions
Java™ Programming Language Preface, slide xx of xxviiCopyright 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Java™ Preface, slide xxi of xxviiCopyrig
overed inlysis and Design
red in SL-110: Language
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Topics Not Covered
• Object-oriented analysis and design – COO-226: Object-Oriented Application AnaUsing UML
• General programming concepts – CoveFundamentals of the Java™ Programming
Java™ Preface, slide xxii of xxviiCopyrig
Bef completedSL g Language, orhav
or C++t editorser, such as
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
How Prepared Are You?
ore attending this course, you should have-110: Fundamentals of the Java™ Programmin
e:
• Created and compiled programs with C• Created and edited text files using a tex• Used a World Wide Web (WWW) brow
Netscape Navigator™
Java™ Preface, slide xxiii of xxviiCopyrig
in this course
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Introductions
• Name• Company affiliation• Title, function, and job responsibility• Experience related to topics presented • Reasons for enrolling in this course• Expectations for this course
Java™ Preface, slide xxiv of xxviiCopyrig
?
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How to Use the Icons
Additional resources
Discussion
Note
Caution
Visual Aid
!
Java™ Preface, slide xxv of xxviiCopyrig
T ymbols
ands, files,mmingtput.and numbersramming coden.es andplaced with a
epresentby the student
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
ypographical Conventions and S
• Courier is used for the names of commdirectories, programming code, prograconstructs, and on-screen computer ou
• Courier bold is used for characters that you type, and for each line of progthat is referenced in a textual descriptio
• Courier italics is used for variablcommand-line placeholders that are rereal name or value.
• Courier italics bold is used to rvariables whose values are to be enteredas part of an activity.
Java™ Preface, slide xxvi of xxviiCopyrig
T ymbols
w words or
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ypographical Conventions and S
• Palatino italics is used for book titles, neterms, or words that are emphasized.
Java™ Preface, slide xxvii of xxviiCopyrig
Jav e followingadd
ethods, and
es unless an.rations,e.g System
soft Windows
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Additional Conventions
a programming language examples use thitional conventions:
• Courier is used for the class names, mkeywords.
• Methods are not followed by parenthesformal or actual parameter list is show
• Line breaks occur where there are sepaconjunctions, or white space in the cod
• If a command on the Solaris™ Operatin(Solaris OS) is different from the Microplatform, both commands are shown.
Sun
Java™ Programmi
Services
ng Language
Module 1
Getting Started
Java™ Module 1, slide 2 of 23Copyrig
ologyechnology
l Machine
a platform that
ne” and “JVM”platform.
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Objectives
• Describe the key features of Java techn• Write, compile, and run a simple Java t
application• Describe the function of the Java Virtua
(JVM™)• Define garbage collection• List the three tasks performed by the Jav
handle code security
NOTE: The terms “Java Virtual Machimean a Virtual Machine for the Java™
Java™ Module 1, slide 3 of 23Copyrig
mplete programs for
g language? improve on
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Relevance
• Is the Java programming language a colanguage or is it useful only for writingthe Web?
• Why do you need another programmin• How does the Java technology platform
other language platforms?
Java™ Module 1, slide 4 of 23Copyrig
ogy?
d applications.
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What Is the Java™ Technol
• Java technology is:• A programming language• A development environment• An application environment• A deployment environment
• It is similar in syntax to C++.• It is used for developing both applets an
Java™ Module 1, slide 5 of 23Copyrig
nology
uages
and clear coder:
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Primary Goals of the Java Tech
• Provides an easy-to-use language by:• Avoiding many pitfalls of other lang• Being object-oriented• Enabling users to create streamlined
• Provides an interpreted environment fo• Improved speed of development• Code portability
Java™ Module 1, slide 6 of 23Copyrig
ology
ead of activitye time they are
ally duringate sources
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Primary Goals of the Java Techn
• Enables users to run more than one thr• Loads classes dynamically; that is, at th
actually needed• Supports changing programs dynamic
runtime by loading classes from dispar• Furnishes better security
Java™ Module 1, slide 7 of 23Copyrig
ology
Th
1.
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Primary Goals of the Java Techn
e following features fulfill these goals:
• The Java Virtual Machine (JVM™)1
• Garbage collection• The Java Runtime Environment (JRE)• JVM tool interface
The terms "Java Virtual Machine" and "JVM" mean a Virtual Machine for the Java platform
Java™ Module 1, slide 8 of 23Copyrig
e
ons
revelopment tool
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The Java Virtual Machin
• Provides hardware platform specificati• Reads compiled byte codes that are
platform-independent• Is implemented as software or hardwa• Is implemented in a Java technology de
or a Web browser
Java™ Module 1, slide 9 of 23Copyrig
JVM
[CPU])
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The Java Virtual Machine
provides definitions for the:
• Instruction set (central processing unit • Register set• Class file format• Stack• Garbage-collected heap• Memory area• Fatal error reporting• High-precision timing support
Java™ Module 1, slide 10 of 23Copyrig
hen the code is
y Suncompliant class
environments.
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The Java Virtual Machine
• The majority of type checking is done wcompiled.
• Implementation of the JVM approved bMicrosystems must be able to run any file.
• The JVM executes on multiple operating
Java™ Module 1, slide 11 of 23Copyrig
ded should be
rogrammer’s
des alocation.aracteristics:ger needed
plementations
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Garbage Collection
• Allocated memory that is no longer needeallocated.
• In other languages, deallocation is the presponsibility.
• The Java programming language provisystem-level thread to track memory al
• Garbage collection has the following ch• Checks for and frees memory no lon• Is done automatically• Can vary dramatically across JVM im
Java™ Module 1, slide 12 of 23Copyrig
ent
Th s follows:
ser
deer
ter
e
are
e
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The Java Runtime Environm
e Java application environment performs aCompile
TestGreeting.java
TestGreeting.class
Load from
Clasload
Bytecoverifi
Interpre
Runtim
Hardw
Runtim
javac
java
hard disk,network,or othersource
Java™ Module 1, slide 13 of 23Copyrig
O -Time (JIT)
e
codeenerator
JIT
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peration of the JRE With a Just-InCompiler
Compile
TestGreeting.java
TestGreeting.class
Classloader
Bytecodeverifier
Interpreter
Runtime
Hardwar
Runtime
javac
java
g
Load fromhard disk,network,or othersource
Java™ Module 1, slide 14 of 23Copyrig
Th
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JVM™ Tasks
e JVM performs three main tasks:
• Loads code• Verifies code• Executes code
Java™ Module 1, slide 15 of 23Copyrig
ution of a
in separate
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The Class Loader
• Loads all classes necessary for the execprogram
• Maintains classes of the local file systemnamespaces
• Prevents spoofing
Java™ Module 1, slide 16 of 23Copyrig
En
ion.rity.flows or
code are
sion of integers
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The Bytecode Verifier
sures that:
• The code adheres to the JVM specificat• The code does not violate system integ• The code causes no operand stack over
underflows.• The parameter types for all operational
correct.• No illegal data conversions (the conver
to pointers) have occurred.
Java™ Module 1, slide 17 of 23Copyrig
n
Th
123456789
Th
12345
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A Simple Java Applicatio
e TestGreeting.java Application
//// Sample "Hello World" application//public class TestGreeting{public static void main (String[] args) {
Greeting hello = new Greeting(); hello.greet(); }}
e Greeting.java Class
public class Greeting {public void greet() {
System.out.println(“hi”); }}
Java™ Module 1, slide 18 of 23Copyrig
tion
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The TestGreetingApplica
• Comment lines• Class declaration• The main method• Method body
Java™ Module 1, slide 19 of 23Copyrig
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The GreetingClass
• Class declaration• The greet method
Java™ Module 1, slide 20 of 23Copyrig
C Greeting
atically.ing command:
rrors.
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ompiling and Running the TestProgram
• Compile TestGreeting.java:javac TestGreeting.java
• The Greeting.java is compiled autom• Run the application by using the follow
java TestGreeting
• Locate common compile and runtime e
Java™ Module 1, slide 21 of 23Copyrig
symbolang.String)ream
estGreetingd
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Compile-Time Errors
• javac: Command not found
• Greeting.java:4: cannot resolvesymbol : method printl (java.llocation: class java.io.PrintStSystem.out.printl("hi");
^
• TestGreet.java:4: Public class Tmust be defined in a file calle"TestGreeting.java".
Java™ Module 1, slide 22 of 23Copyrig
in
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Runtime Errors
• Can’t find class TestGreeting
• Exception in thread "main"java.lang.NoSuchMethodError: ma
Java™ Module 1, slide 23 of 23Copyrig
ronment
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Java Technology Runtime Envi
Com
pile
TestGreeting.java
TestGreeting.class
Run
time
Greeting.class
Greeting.java
JVM
UNIX® DOS JavaOS™
JVMJVM
javac
java
Also compiles
Also loads
Can run on multiple platforms
Sun
Java™ Programmi
ming
Services
ng Language
Module 2
Object-Oriented Program
Java™ Module 2, slide 2 of 26Copyrig
ncapsulation,
ogy application
onstructor, and
public assulation
ogramming
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Objectives
• Define modeling concepts: abstraction, eand packages
• Discuss why you can reuse Java technolcode
• Define class, member, attribute, method, cpackage
• Use the access modifiers private andappropriate for the guidelines of encap
• Invoke a method on a particular object• Use the Java technology application pr
interface (API) online documentation
Java™ Module 2, slide 3 of 26Copyrig
e analysis and
and code reuse?ing language
language?
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Relevance
• What is your understanding of softwardesign?
• What is your understanding of design• What features does the Java programm
possess that make it an object-oriented• Define the term object-oriented.
Java™ Module 2, slide 4 of 26Copyrig
0s–Up)soft Windows
penLook
JDBC™
Java
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Software Engineering
Machine Code (Late 1940s–Up)
High-Level Languages (1950s–Up) Operating Systems (196
Libraries / Functional APIs (1960s–Early 1980s)
Object-Oriented Languages (1980s–Up)
Toolkits / Frameworks / Object APIs (1990s–Up)
Fortran LISP C UNIX MicroMacOS
NASTRAN X-Windows
COBOL
TCP/IP ISAM O
SELF Smalltalk Common Lisp Object System Eiffel
AWT / J.F.C./Swing Jini™ JavaBeans™Java 2 SDK
C++
OS/360
Java™ Module 2, slide 5 of 26Copyrig
ase
ds to do:tors and
t:ractionsstemimplify the
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The Analysis and Design Ph
• Analysis describes what the system neeModeling the real-world, including acactivities, objects, and behaviors
• Design describes how the system does i• Modeling the relationships and inte
between objects and actors in the sy• Finding useful abstractions to help s
problem or solution
Java™ Module 2, slide 6 of 26Copyrig
e used in many
tes and
of objects thats can be usedbehavior
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Abstraction
• Functions – Write an algorithm once to bsituations
• Objects – Group a related set of attribubehaviors into a class
• Frameworks and APIs – Large groups support a complex activity; Frameworkas is or be modified to extend the basic
Java™ Module 2, slide 7 of 26Copyrig
jects
s a device fromructed.n object:object includes.each object
e key features:
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Classes as Blueprints for Ob
• In manufacturing, a blueprint describewhich many physical devices are const
• In software, a class is a description of a• A class describes the data that each • A class describes the behaviors that
exhibits.• In Java technology, classes support thre
of object-oriented programming (OOP)• Encapsulation• Inheritance• Polymorphism
Java™ Module 2, slide 8 of 26Copyrig
lasses
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Declaring Java Technology C
• Basic syntax of a Java class:<modifier>* class <class_name> {
<attribute_declaration>*<constructor_declaration>*<method_declaration>*
}
• Example:1 public class Vehicle {2 private double maxLoad;3 public void setMaxLoad(double value) {4 maxLoad = value;5 }6 }
Java™ Module 2, slide 9 of 26Copyrig
e>];
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Declaring Attributes
• Basic syntax of an attribute:<modifier>* <type> <name> [ = <initial_valu
• Examples:1 public class Foo {2 private int x;3 private float y = 10000.0F;4 private String name = "Bates Motel";5 }
Java™ Module 2, slide 10 of 26Copyrig
t>* ) {
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Declaring Methods
• Basic syntax of a method:<modifier>* <return_type> <name> ( <argumen
<statement>*}
• Examples:1 public class Dog {2 private int weight;3 public int getWeight() {4 return weight;5 }6 public void setWeight(int newWeight) {7 if ( newWeight > 0 ) {8 weight = newWeight;9 }10 }11 }
Java™ Module 2, slide 11 of 26Copyrig
rs
r>
ncluding
s public
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Accessing Object Membe
• The dot notation is: <object>.<membe• This is used to access object members, i
attributes and methods.• Examples of dot notation are:
d.setWeight(42);d.weight = 42; // only permissible if weight i
Java™ Module 2, slide 12 of 26Copyrig
Th
+
+
+
t access to to a MyDate
ound
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Information Hiding
e problem:
MyDate
day : int
month : int
year : int
Client code has direcinternal data (d refersobject):
d.day = 32;// invalid day
d.month = 2; d.day = 30;// plausible but wrong
d.day = d.day + 1;// no check for wrap ar
Java™ Module 2, slide 13 of 26Copyrig
Th setters andnal data:
false
e if wrap around
+
+
+
+
+
+
-d
-m
-y
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Information Hiding
e solution:Client code must usegetters to access inter
MyDate d = new MyDate();
d.setDay(32);// invalid day, returns
d.setMonth(2);d.setDay(30);// plausible but wrong,// setDay returns false
d.setDay(d.getDay() + 1);// this will return fals// needs to occur
setDay(int) : boolean
setYear(int) : boolean
setMonth(int) : boolean
getDay() : int
getMonth() : int
getYear() : int
MyDate
ay : int
onth : int
ear : int
Verify days in month
Java™ Module 2, slide 14 of 26Copyrig
lasscess data
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Encapsulation
• Hides the implementation details of a c• Forces the user to use an interface to ac• Makes the code more maintainable
+setDay(int) : boolean
+setYear(int) : boolean
+setMonth(int) : boolean
+getDay() : int
+getMonth() : int
+getYear() : int
MyDate
-date : long
-isDayValid(int) : boolean
Java™ Module 2, slide 15 of 26Copyrig
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Declaring Constructors
• Basic syntax of a constructor:[<modifier>] <class_name> ( <argument>* ) {<statement>*
}
• Example:1 public class Dog {23 private int weight;45 public Dog() {6 weight = 42;7 }8 }
Java™ Module 2, slide 16 of 26Copyrig
r
in every class.ructors, thecally:umentstyinstances with
onstructor.
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The Default Constructo
• There is always at least one constructor• If the writer does not supply any const
default constructor is present automati• The default constructor takes no arg• The default constructor body is emp
• The default enables you to create objectnew Xxx()without having to write a c
Java™ Module 2, slide 17 of 26Copyrig
ort.java file
{...}
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Source File Layout
• Basic syntax of a Java source file is:[<package_declaration>]<import_declaration>*<class_declaration>+
• For example, the VehicleCapacityRepis:1 package shipping.reports;23 import shipping.domain.*;4 import java.util.List;5 import java.io.*;67 public class VehicleCapacityReport {8 private List vehicles;9 public void generateReport(Writer output)10 }
Java™ Module 2, slide 18 of 26Copyrig
ystems.ackages.
icle
RiverBarge
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Software Packages
• Packages help manage large software s• Packages can contain classes and sub-p
Veh
Truck
Company Owns 0..*
shipping
domaingui
reports
Java™ Module 2, slide 19 of 26Copyrig
t
is:
eginning of the
ce file. is placed into
d separated by
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The packageStatemen
• Basic syntax of the package statement package <top_pkg_name>[.<sub_pkg_name>]*;
• Examples of the statement are:package shipping.gui.reportscreens;
• Specify the package declaration at the bsource file.
• Only one package declaration per sour• If no package is declared, then the class
the default package.• Package names must be hierarchical an
dots.
Java™ Module 2, slide 20 of 26Copyrig
:name>;
g:
ses
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The importStatement
• Basic syntax of the import statement isimport <pkg_name>[.<sub_pkg_name>]*.<class_ORimport <pkg_name>[.<sub_pkg_name>]*.*;
• Examples of the statement are:import java.util.List;import java.io.*;import shipping.gui.reportscreens.*;
• The import statement does the followin• Precedes all class declarations• Tells the compiler where to find clas
Java™ Module 2, slide 21 of 26Copyrig
ges
containing the
packages.
.class
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Directory Layout and Packa
• Packages are stored in the directory treepackage name.
• An example is the shipping applicationshipping/
domain/
gui/
reports/
Vehicle.classRiverBarge.classTruck.class
VehicleCapacityReport
Company.class
Java™ Module 2, slide 22 of 26Copyrig
J
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
DevelopmentavaProjects/
ShippingPrj/
src/
docs/
shipping/
domain/gui/reports/
classes/
shipping/
domain/gui/reports/
Java™ Module 2, slide 23 of 26Copyrig
tion
va
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Compiling Using the -dOp
cd JavaProjects/ShippingPrj/srcjavac -d ../classes shipping/domain/*.ja
Java™ Module 2, slide 24 of 26Copyrig
run-time object
;iable, and data
bject;roceduresed to initialize
b-packages
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Terminology Recap
• Class – The source-code blueprint for a• Object – An instance of a class;
also known as instance• Attribute – A data element of an object
also known as data member, instance varfield
• Method – A behavioral element of an oalso known as algorithm, function, and p
• Constructor – A method-like construct ua new object
• Package – A grouping of classes and su
Java™ Module 2, slide 25 of 26Copyrig
API
HTML) files
s hyperlinks tot package.rarchy, avariables, a list
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Using the Java TechnologyDocumentation
• A set of Hypertext Markup Language (provides information about the API.
• A frame describes a package and containinformation describing each class in tha
• A class document includes the class hiedescription of the class, a list of memberof constructors, and so on.
Sun Services
Java Technology APIDocumentation With HTML3
Java™ Programming Language Module 2, slide 26 of 26Copyright 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Sun
Java™ Programmi
Id Types
Services
ng Language
Module 3
entifiers, Keywords, and
Java™ Module 3, slide 2 of 37Copyrig
identifiers
xtual typeseference variable
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Objectives
• Use comments in a source program• Distinguish between valid and invalid • Recognize Java technology keywords• List the eight primitive types• Define literal values for numeric and te• Define the terms primitive variable and r
Java™ Module 3, slide 3 of 37Copyrig
variableiables of class
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Objectives
• Declare variables of class type• Construct an object using new• Describe default initialization• Describe the significance of a reference• State the consequences of assigning var
type
Java™ Module 3, slide 4 of 37Copyrig
n variableswith object
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Relevance
• Do you know the primitive Java types?• Can you describe the difference betwee
holding primitive values as compared references?
Java™ Module 3, slide 5 of 37Copyrig
Th ava technologypro
// c
/* c* o*/
/** * */
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Comments
e three permissible styles of comment in a Jgram are:
omment on one line
omment on oner more lines
documentation commentcan also span one or more lines
Java™ Module 3, slide 6 of 37Copyrig
Space
terminated by
nd by opening
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Semicolons, Blocks, and White
• A statement is one or more lines of codea semicolon (;):totals = a + b + c
+ d + e + f;
• A block is a collection of statements bouand closing braces:{ x = y + 1; y = x + 1;}
Java™ Module 3, slide 7 of 37Copyrig
Space
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Semicolons, Blocks, and White
• A class definition uses a special block:public class MyDate { private int day; private int month; private int year;}
• You can nest block statements.while ( i < large ) {a = a + i;// nested blockif ( a == max ) {b = b + a;a = 0;
}i = i + 1;
}
Java™ Module 3, slide 8 of 37Copyrig
Space
in a Java
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Semicolons, Blocks, and White
• Any amount of white space is permittedprogram.For example:{int x;x=23*54;}
is equivalent to:{int x;
x = 23 * 54;}
Java™ Module 3, slide 9 of 37Copyrig
Ide
methodcore (_), or
m length
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Identifiers
ntifiers have the following characteristics:
• Are names given to a variable, class, or• Can start with a Unicode letter, unders
dollar sign ($)• Are case-sensitive and have no maximu• Examples:
identifieruserNameuser_name_sys_var1$change
Java™ Module 3, slide 10 of 37Copyrig
eywords
Re e
abs switch
ass synchronized
boo this
bre d throw
byt throws
cas transient
cat try
cha void
cla volatile
con while
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Java Programming Language K
served literal words: null, true, and fals
tract continue for new
ert default goto package
lean do if private
ak double implements protecte
e else import public
e enum instanceof return
ch extends int short
r final interface static
ss finally long strictfp
st float native super
Java™ Module 3, slide 11 of 37Copyrig
Th t primitivetyp
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Primitive Types
e Java programming language defines eighes:
• Logical – boolean• Textual – char• Integral – byte, short, int, and long
• Floating – double and float
Java™ Module 3, slide 12 of 37Copyrig
Th acteristics:
, true and
n type and
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Logical – boolean
e boolean primitive has the following char
• The boolean data type has two literalsfalse.
• For example, the statement:boolean truth = true;
declares the variable truth as booleaassigns it a value of true.
Java™ Module 3, slide 13 of 37Copyrig
Th characteristics:
quotes (’ ’)
is replaced with
letter phi [Φ].
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Textual – char
e textual char primitive has the following
• Represents a 16-bit Unicode character• Must have its literal enclosed in single • Uses the following notations:
'a' The letter a
'\t' The tab character
'\u????' A specific Unicode character, ????, exactly four hexadecimal digits .For example, ’\u03A6’ is the Greek
Java™ Module 3, slide 14 of 37Copyrig
Th aracteristics:
s (" ")
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Textual – String
e textual String type has the following ch
• Is not a primitive data type; it is a class• Has its literal enclosed in double quote
"The quick brown fox jumps over the lazy dog."
• Can be used as follows:String greeting = "Good Morning !! \n";String errorMessage = "Record Not Found !";
Java™ Module 3, slide 15 of 37Copyrig
d long
Th aracteristics:
mal, octal, or
long.
e.
al value.
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Integral – byte, short, int, an
e integral primitives have the following ch
• Integral primates use three forms: Decihexadecimal
• Literals have a default type of int.
• Literals with the suffix L or l are of type
2 The decimal form for the integer 2.
077 The leading 0 indicates an octal valu
0xBAAC The leading 0x indicates a hexadecim
Java™ Module 3, slide 16 of 37Copyrig
d long
ranges:
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Integral – byte, short, int, an
• Integral data types have the following
Integer Length Name or Type Range
8 bits byte -27 to 27-1
16 bits short -215 to 215 -1
32 bits int -231 to 231 -1
64 bits long -263 to 263 -1
Java™ Module 3, slide 17 of 37Copyrig
ouble
Th ngcha
ecimal point or
ouble)
dant D
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Floating Point – floatand d
e floating point primitives have the followiracteristics:
• Floating-point literal includes either a done of the following:• E or e (add exponential value)• F or f (float)• D or d (double)
3.14 A simple floating-point value (a d
6.02E23 A large floating-point value
2.718F A simple float size value
123.4E+306D A large double value with redun
Java™ Module 3, slide 18 of 37Copyrig
ouble
owing sizes:
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Floating Point – floatand d
• Literals have a default type of double.• Floating-point data types have the foll
Float Length Name or Type
32 bits float
64 bits double
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Variables, Declarations, andAssignments
1 public class Assign {2 public static void main (String args []) {3 // declare integer variables4 int x, y;5 // declare and assign floating point6 float z = 3.414f;7 // declare and assign double8 double w = 3.1415;9 // declare and assign boolean10 boolean truth = true;11 // declare character variable12 char c;13 // declare String variable14 String str;15 // declare and assign String variable16 String str1 = "bye";17 // assign value to char variable18 c = 'A';19 // assign value to String variable20 str = "Hi out there!";21 // assign values to int variables22 x = 6;23 y = 1000;24 }25 }
Java™ Programming Language Module 3, slide 19 of 37Copyright 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Java™ Module 3, slide 20 of 37Copyrig
pes all others
n object.
r) { ... }
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Java Reference Types
• In Java technology, beyond primitive tyare reference types.
• A reference variable contains a handle to a• For example:
1 public class MyDate {2 private int day = 1;3 private int month = 1;4 private int year = 2000;5 public MyDate(int day, int month, int yea6 public String toString() { ... }7 }
1 public class TestMyDate {2 public static void main(String[] args) {3 MyDate today = new MyDate(22, 7, 1964);4 }5 }
Java™ Module 3, slide 21 of 37Copyrig
bjects
ing actions:
rformed.
the new
o a variable.
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Constructing and Initializing O
• Calling new Xyz() performs the followa. Memory is allocated for the object.b. Explicit attribute initialization is pec. A constructor is executed.d. The object reference is returned by
operator.• The reference to the object is assigned t• An example is:
MyDate my_birth = new MyDate(22, 7, 1964);
Java™ Module 3, slide 22 of 37Copyrig
out
a reference:
for MyDate:
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Memory Allocation and Lay
• A declaration allocates storage only forMyDate my_birth = new MyDate(22, 7, 1964);
• Use the new operator to allocate space MyDate my_birth = new MyDate(22, 7, 1964);
my_birth ????
my_birth ????
day
month
year
0
0
0
Java™ Module 3, slide 23 of 37Copyrig
ion
ttribute
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Explicit Attribute Initializat
• Initialize the attributes as follows:MyDate my_birth = new MyDate(22, 7, 1964);
• The default values are taken from the adeclaration in the class.
my_birth ????
day
month
year
1
1
2000
Java™ Module 3, slide 24 of 37Copyrig
or
llows:
r, the first
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Executing the Construct
• Execute the matching constructor as foMyDate my_birth = new MyDate(22, 7, 1964);
• In the case of an overloaded constructoconstructor can call another.
my_birth ????
day
month
year
22
7
1964
Java™ Module 3, slide 25 of 37Copyrig
eference
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Assigning a Variable
• Assign the newly created object to the rvariable as follows:MyDate my_birth = new MyDate(22, 7, 1964);
my_birth 0x01abcdef
day
month
year
22
7
1964
Java™ Module 3, slide 26 of 37Copyrig
nt to two
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Assigning References
• Two variables refer to a single object:1 int x = 7;2 int y = x;3 MyDate s = new MyDate(22, 7, 1964);4 MyDate t = s;
• Reassignment makes two variables poiobjects:5 t = new MyDate(22, 12, 1964);
x 7
y 7
s 0x01234567
t 0x01234567
22 7 1964
x 7
y 7
s 0x01234567
t 0x12345678
22 7 1964
22 12 1964
Java™ Module 3, slide 27 of 37Copyrig
ogramminglue. argument to areference to the
d in the callede is never
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Pass-by-Value
• In a single virtual machine, the Java prlanguage only passes arguments by va
• When an object instance is passed as anmethod, the value of the argument is aobject.
• The contents of the object can be changemethod, but the original object referencchanged.
Java™ Module 3, slide 28 of 37Copyrig
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Pass-by-Value
public class PassTest {
// Methods to change the current values public static void changeInt(int value) { value = 55; } public static void changeObjectRef(MyDate ref) { ref = new MyDate(1, 1, 2000); } public static void changeObjectAttr(MyDate ref){ ref.setDay(4); }
Java™ Module 3, slide 29 of 37Copyrig
1314151617181920212223
Th
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Pass-by-Value
public static void main(String args[]) { MyDate date; int val;
// Assign the int val = 11; // Try to change it changeInt(val); // What is the current value? System.out.println("Int value is: " + val);
e result of this output is:
Int value is: 11
Java™ Module 3, slide 30 of 37Copyrig
24252627282930
Th
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Pass-by-Value
// Assign the date date = new MyDate(22, 7, 1964); // Try to change it changeObjectRef(date); // What is the current value?
System.out.println("MyDate: " + date);
e result of this output is:
MyDate: 22-7-1964
Java™ Module 3, slide 31 of 37Copyrig
3132333435363738
Th
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Pass-by-Value
// Now change the day attribute // through the object reference changeObjectAttr(date); // What is the current value?
System.out.println("MyDate: " + date);}
}
e result of this output is:
MyDate: 4-7-1964
Java™ Module 3, slide 32 of 37Copyrig
He
variables and
er to another
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The thisReference
re are a few uses of the this keyword:
• To resolve ambiguity between instanceparameters
• To pass the current object as a parametmethod or constructor
Java™ Module 3, slide 33 of 37Copyrig
123456789101112131415
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The thisReference
public class MyDate { private int day = 1; private int month = 1; private int year = 2000;
public MyDate(int day, int month, int year) { this.day = day; this.month = month; this.year = year; } public MyDate(MyDate date) { this.day = date.day; this.month = date.month; this.year = date.year; }
Java™ Module 3, slide 34 of 37Copyrig
1617181920212223242526
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The thisReference
public MyDate addDays(int moreDays) { MyDate newDate = new MyDate(this); newDate.day = newDate.day + moreDays; // Not Yet Implemented: wrap around code... return newDate; }public String toString() {
return "" + day + "-" + month + "-" + year; }}
Java™ Module 3, slide 35 of 37Copyrig
12345678
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The thisReference
public class TestMyDate { public static void main(String[] args) { MyDate my_birth = new MyDate(22, 7, 1964); MyDate the_next_week = my_birth.addDays(7);
System.out.println(the_next_week); }}
Java™ Module 3, slide 36 of 37Copyrig
Coding
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Java Programming LanguageConventions
• Packages:com.example.domain;
• Classes, interfaces, and enum types:SavingsAccount
• Methods:getAccount()
• Variables:currentCustomer
• Constants:HEAD_COUNT
Java™ Module 3, slide 37 of 37Copyrig
Coding
on.
ss members.
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Java Programming LanguageConventions
• Control structures:if ( condition ) {statement1;
} else {statement2;
}
• Spacing:• Use one statement per line.• Use two or four spaces for indentati
• Comments:• Use // to comment inline code.• Use /** documentation */ for cla
Sun
Java™ Programmi
ontrol
Services
ng Language
Module 4
Expressions and Flow C
Java™ Module 4, slide 2 of 31Copyrig
variablesablesence before
are operatorsssignments of
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Objectives
• Distinguish between instance and local• Describe how to initialize instance vari• Identify and correct a Possible refer
assignment compiler error• Recognize, describe, and use Java softw• Distinguish between legal and illegal a
primitive types
Java™ Module 4, slide 3 of 31Copyrig
requirements
d required casts
structions andue as flow
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Objectives
• Identify boolean expressions and theirin control constructs
• Recognize assignment compatibility anin fundamental types
• Use if, switch, for, while, and do conthe labeled forms of break and contincontrol structures in a program
Java™ Module 4, slide 4 of 31Copyrig
ogrammers?th the same
ed in otherguages use to
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Relevance
• What types of variables are useful to pr• Can multiple classes have variables wi
name and, if so, what is their scope?• What types of control structures are us
languages? What methods do these lancontrol flow?
Java™ Module 4, slide 5 of 31Copyrig
Lo
od and arek variableshod is executedd
Va :
ation.atically.
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Variables and Scope
cal variables are:
• Variables that are defined inside a methcalled local, automatic, temporary, or stac
• Variables that are created when the metare destroyed when the method is exite
riable initialization comprises the following
• Local variables require explicit initializ• Instance variables are initialized autom
Java™ Module 4, slide 6 of 31Copyrig
epub p
p
} p
}}
pubp
}}
Heap Memory
ScopeExample
i 1
ack
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Variable Scope Exampllic class ScopeExample {rivate int i=1;
ublic void firstMethod() { int i=4, j=5;
this.i = i + j; secondMethod(7);
ublic void secondMethod(int i) {int j=8; this.i = i + j;
lic class TestScoping {ublic static void main(String[] args) {ScopeExample scope = new ScopeExample();
scope.firstMethod();
main
firstMethod
i
j
secondMethod
i
j
this
this
scope
4
5
7
8
Execution St
Java™ Module 4, slide 7 of 31Copyrig
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Variable Initialization
Variable Value
byte 0
short 0
int 0
long 0L
float 0.0F
double 0.0D
char '\u0000'
boolean false
All reference types null
Java™ Module 4, slide 8 of 31Copyrig
ciple
Th ave beenini
javTest en initialized 1 er
345678910 ation11
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Initialization Before Use Prin
e compiler will verify that local variables htialized before used.
ac TestInitBeforeUse.javaInitBeforeUse.java:10: variable y might not have bez = y + x; // Possible use before initialization ^ror
public void doComputation() { int x = (int)(Math.random() * 100); int y; int z; if (x > 50) { y = 9; } z = y + x; // Possible use before initializ }
Java™ Module 4, slide 9 of 31Copyrig
Op ssociative++ to L* to R+ to R<< to R< to R== to R& to R^ to R| to R&& to R|| to R<b to L= * to L
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Operator Precedence
erators A-- + unary - unary ~ ! (<data_type>) R/ % L- L>> >>> L> <= >= instanceof L!= L
LLLLL
oolean_expr> ? <expr1> : <expr2> R= /= %= += -= <<= >>= >>>= &= ^= |= R
Java™ Module 4, slide 10 of 31Copyrig
e:
:
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Logical Operators
• The boolean operators are:! – NOT & – AND| – OR ^ – XOR
• The short-circuit boolean operators ar&& – AND || – OR
• You can use these operators as followsMyDate d = reservation.getDepartureDate();if ( (d != null) && (d.day > 31) {// do something with d
}
Java™ Module 4, slide 11 of 31Copyrig
s
0 1
1 1
0 1
0 1
1 1
1 1
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Bitwise Logical Operator
• The integer bitwise operators are:~ – Complement & – AND^ – XOR | – OR
• Byte-sized examples include:
0 0 01 1 1 1 1
1 1 10 0 0 0 0
~
0 0 01 1 1
0 0 01 1 1
0 0 0 0 1 1
&
0 0 01 1 1
0 0 01 1 1|
0 01 1 1 1
0 0 0 01 1 1 1
0 0 01 1 1 1 1
0 0 0 00 11 1
^
Java™ Module 4, slide 12 of 31Copyrig
>>>
rator:
ft.rator:. shift.
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Right-Shift Operators >>and
• Arithmetic or signed right shift (>>) ope• Examples are:
128 >> 1 returns 128/21 = 64256 >> 4 returns 256/24 = 16-256 >> 4 returns -256/24 = -16
• The sign bit is copied during the shi• Logical or unsigned right-shift (>>>) ope
• This operator is used for bit patterns• The sign bit is not copied during the
Java™ Module 4, slide 13 of 31Copyrig
s:
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Left-Shift Operator <<
• Left-shift (<<) operator works as follow128 << 1 returns 128 * 21 = 25616 << 2 returns 16 * 22 = 64
Java™ Module 4, slide 14 of 31Copyrig
s
0 10 0 1 1
1 1
0
00
11
1111
0
00
13
-13
135
-135
13
-13
1111 00011 1
1 1001
0 0111 0000 0
10 1 10
0 0111 0000 0
1111 00011 1
0 00 0 0
0 00 0 0
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Shift Operator Example
1
1
0
0
00 0 000 0 000 0 000 0 0
11 1 1 11 1 111 1 1 11 1 1 11 1 1
00 0 01357 =
-1357 =
57 >> 5 =
57 >> 5 =
7 >>> 5 =
7 >>> 5 =
57 << 5 =
57 << 5 =
11 1 1 111 1 1 11 1 1 11 1 1
1111 00011 1 1 11 1 111 1 11 1 1
000 0 000 0 000 0 000 0 0
0 0111 0000 0 000 0 000 0 000 0
0 00 0 0
11 1 11
000 0 000 0 000 0 000 0 00 00 0 0
11 1 1 111 1 1 11 1 1 11 1 10 00 0 0
Java™ Module 4, slide 15 of 31Copyrig
h +
.bjects
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String Concatenation Wit
• The + operator works as follows:• Performs String concatenation• Produces a new String:
String salutation = "Dr.";String name = "Pete" + " " + "Seymour";String title = salutation + " " + name;
• One argument must be a String object• Non-strings are converted to String o
automatically.
Java™ Module 4, slide 16 of 31Copyrig
nment, theent with a cast. requires an
a cast
a cast
ger literal
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Casting
• If information might be lost in an assigprogrammer must confirm the assignm
• The assignment between long and intexplicit cast.long bigValue = 99L;int squashed = bigValue; // Wrong, needsint squashed = (int) bigValue; // OK
int squashed = 99L; // Wrong, needsint squashed = (int) 99L; // OK, but...int squashed = 99; // default inte
Java™ Module 4, slide 17 of 31Copyrig
essions
o a longer form
e variable type bits) as the
l
egal
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Promotion and Casting of Expr
• Variables are promoted automatically t(such as int to long).
• Expression is assignment-compatible if this at least as large (the same number ofexpression type.long bigval = 6; // 6 is an int type, OKint smallval = 99L; // 99L is a long, illega
double z = 12.414F; // 12.414F is float, OKfloat z1 = 12.414; // 12.414 is double, ill
Java™ Module 4, slide 18 of 31Copyrig
nts
Th
if <
Ex
if (Sy
or
if (Sy
}
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Simple if, elseStateme
e if statement syntax:
( <boolean_expression> )statement_or_block>
ample:
x < 10 )stem.out.println("Are you finished yet?");
(recommended):
x < 10 ) {stem.out.println("Are you finished yet?");
Java™ Module 4, slide 19 of 31Copyrig
ents
Th
if <
els<
Ex
if (Sy
} elSy
}
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Complex if, elseStatem
e if-else statement syntax:
( <boolean_expression> )statement_or_block>estatement_or_block>
ample:
x < 10 ) {stem.out.println("Are you finished yet?");se {stem.out.println("Keep working...");
Java™ Module 4, slide 20 of 31Copyrig
ents
Th
if <
els<
Ex
int sif (Sy ;
} elSy
} elSy
}
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Complex if, elseStatem
e if-else-if statement syntax:
( <boolean_expression> )statement_or_block>e if ( <boolean_expression> )statement_or_block>
ample:
count = getCount(); // a method defined in the clascount < 0) {stem.out.println("Error: count value is negative.")se if (count > getMaxCount()) {stem.out.println("Error: count value is too big.");se {stem.out.println("There will be " + count +
" people for lunch today.");
Java™ Module 4, slide 21 of 31Copyrig
Th
swic
c
d
}
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Switch Statements
e switch statement syntax:
tch ( <expression> ) {ase <constant1>:<statement_or_block>*[break;]
ase <constant2>:<statement_or_block>*[break;]
efault:<statement_or_block>*[break;]
Java™ Module 4, slide 22 of 31Copyrig
A s
switca
ca
de
}
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Switch Statements
witch statement example:
ch ( carModel ) {se DELUXE:addAirConditioning();addRadio();addWheels();addEngine();break;se STANDARD:addRadio();addWheels();addEngine();break;fault:addWheels();addEngine();
Java™ Module 4, slide 23 of 31Copyrig
Th vious example:
switca
ca
de
}
Wi falls througheac
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Switch Statements
is switch statement is equivalent to the pre
ch ( carModel ) {se DELUXE:addAirConditioning();se STANDARD:addRadio();fault:addWheels();addEngine();
thout the break statements, the execution h subsequent case clause.
Java™ Module 4, slide 24 of 31Copyrig
Th
for<
Ex
for Sy
or
for Sy
}
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Looping Statements
e for loop:
( <init_expr>; <test_expr>; <alter_expr> )statement_or_block>
ample:
( int i = 0; i < 10; i++ )stem.out.println(i + " squared is " + (i*i));
(recommended):
( int i = 0; i < 10; i++ ) {stem.out.println(i + " squared is " + (i*i));
Java™ Module 4, slide 25 of 31Copyrig
Th
whi<
Ex
int whilSyi+
}
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Looping Statements
e while loop:
le ( <test_expr> )statement_or_block>
ample:
i = 0;e ( i < 10 ) {stem.out.println(i + " squared is " + (i*i));+;
Java™ Module 4, slide 26 of 31Copyrig
Th
do<
whi
Ex
intdo {Syi+
} wh
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Looping Statements
e do/while loop:
statement_or_block>le ( <test_expr> );
ample:
i = 0;
stem.out.println(i + " squared is " + (i*i));+;ile ( i < 10 );
Java™ Module 4, slide 27 of 31Copyrig
ol
dand, where
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Special Loop Flow Contr
• The break [<label>]; command• The continue [<label>]; comman• The <label> : <statement> comm
<statement> should be a loop
Java™ Module 4, slide 28 of 31Copyrig
1234567
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The breakStatement
do {statement;if ( condition ) {break;
}statement;
} while ( test_expr );
Java™ Module 4, slide 29 of 31Copyrig
t
1234567
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The continueStatemen
do {statement;if ( condition ) {continue;
}statement;
} while ( test_expr );
Java™ Module 4, slide 30 of 31Copyrig
Labels
123456789101112
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Using breakStatements with
outer:do {statement1;do {statement2;if ( condition ) {break outer;
}statement3;
} while ( test_expr );statement4;
} while ( test_expr );
Java™ Module 4, slide 31 of 31Copyrig
th Labels
123456789101112
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Using continueStatements wi
test:do {statement1;do {statement2;if ( condition ) {continue test;
}statement3;
} while ( test_expr );statement4;
} while ( test_expr );
Sun
Java™ Programmi
Services
ng Language
Module 5
Arrays
Java™ Module 5, slide 2 of 15Copyrig
class, or array
nitializedf an arrayn array
ne array to
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Objectives
• Declare and create arrays of primitive, types
• Explain why elements of an array are i• Explain how to initialize the elements o• Determine the number of elements in a• Create a multidimensional array• Write code to copy array values from o
another
Java™ Module 5, slide 3 of 15Copyrig
Wh
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Relevance
at is the purpose of an array?
Java™ Module 5, slide 4 of 15Copyrig
es:
new.
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Declaring Arrays
• Group data objects of the same type.• Declare arrays of primitive or class typ
char s[];Point p[];
char[] s;Point[] p;
• Create space for a reference.• An array is an object; it is created with
Java™ Module 5, slide 5 of 15Copyrig
Us .
For
12345678910
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Creating Arrays
e the new keyword to create an array object
example, a primitive (char) array:
public char[] createArray() {char[] s;
s = new char[26];for ( int i=0; i<26; i++ ) {s[i] = (char) (’A’ + i);
}
return s;}
Java™ Module 5, slide 6 of 15Copyrig
C imitives
ory
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reating an Array of Character Pr
main
createArray s
this
char[]
A
Execution Stack
Heap Mem
B
C
D
Z
Java™ Module 5, slide 7 of 15Copyrig
ys
An
12345678910
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Creating Reference Arra
other example, an object array:
public Point[] createArray() {Point[] p;
p = new Point[10];for ( int i=0; i<10; i++ ) {p[i] = new Point(i, i+1);
}
return p;}
Java™ Module 5, slide 8 of 15Copyrig
C imitives
nt
0
1
Point
x
y
1
2
int
2
3
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
reating an Array of Character PrWith PointObjects
main
createArray p
this
Point[]
Execution Stack
Heap Memory
Poi
x
y
Po
x
y
Java™ Module 5, slide 9 of 15Copyrig
Strnamnamnamnam
{
MyDdatdatdatdat
{, 7, 1964), 1, 2000),, 12, 1964)
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Initializing Arrays
• Initialize an array element.• Create an array with initial values.ing[] names;es = new String[3];es[0] = "Georgianna";es[1] = "Jen";es[2] = "Simon";
String[] names = "Georgianna","Jen","Simon"
};
ate[] dates;es = new MyDate[3];es[0] = new MyDate(22, 7, 1964);es[1] = new MyDate(1, 1, 2000);es[2] = new MyDate(22, 12, 1964);
MyDate[] dates = new MyDate(22new MyDate(1,new MyDate(22
};
Java™ Module 5, slide 10 of 15Copyrig
Ar
int[twoDtwoD
int[
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Multidimensional Arrays
rays of arrays:
][] twoDim = new int[4][];im[0] = new int[5];im[1] = new int[5];
][] twoDim = new int[][4]; // illegal
Java™ Module 5, slide 11 of 15Copyrig
h:
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Multidimensional Arrays
• Non-rectangular arrays of arrays:twoDim[0] = new int[2];twoDim[1] = new int[4];twoDim[2] = new int[6];twoDim[3] = new int[8];
• Array of four arrays of five integers eacint[][] twoDim = new int[4][5];
Java™ Module 5, slide 12 of 15Copyrig
All
publfo
}}
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Array Bounds
array subscripts begin at 0:
ic void printElements(int[] list) {r (int i = 0; i < list.length; i++) {System.out.println(list[i]);
Java™ Module 5, slide 13 of 15Copyrig
oop
Jav rsion 5.0int over arrays:
publfo
}}
Th in list do.
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Using the Enhanced forL
a 2 Platform, Standard Edition (J2SE™) veroduced an enhanced for loop for iterating
ic void printElements(int[] list) {r ( int element : list ) {System.out.println(element);
e for loop can be read as for each element
Java™ Module 5, slide 14 of 15Copyrig
e to refer to an
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Array Resizing
• You cannot resize an array.• You can use the same reference variabl
entirely new array, such as:int[] myArray = new int[6];myArray = new int[10];
Java™ Module 5, slide 15 of 15Copyrig
Th rays is:
123456789 h);
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Copying Arrays
e System.arraycopy() method to copy ar
//original arrayint[] myArray = { 1, 2, 3, 4, 5, 6 };
// new larger arrayint[] hold = { 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 };
// copy all of the myArray array to the hold// array, starting with the 0th indexSystem.arraycopy(myArray, 0, hold, 0, myArray.lengt
Sun
Java™ Programmi
Services
ng Language
Module 6
Class Design
Java™ Module 6, slide 2 of 43Copyrig
ding, overriding,
nd the default
d method
on and
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Objectives
• Define inheritance, polymorphism, overloaand virtual method invocation
• Use the access modifiers protected a(package-friendly)
• Describe the concepts of constructor anoverloading
• Describe the complete object constructiinitialization operation
Java™ Module 6, slide 3 of 43Copyrig
Ho pport objectinh
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Relevance
w does the Java programming language sueritance?
Java™ Module 6, slide 4 of 43Copyrig
Th
";
ls() {...}
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Subclassing
e Employee class is shown here.
public class Employee { public String name = " public double salary; public Date birthDate;
public String getDetai}
Employee
+name : String = ""
+salary : double
+birthDate : Date
+getDetails() : String
Java™ Module 6, slide 5 of 43Copyrig
Th
";
nt;
ls() {...}
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Subclassing
e Manager class is shown here.
public class Manager { public String name = " public double salary; public Date birthDate; public String departme
public String getDetai}
Manager
+name : String = ""
+salary : double
+birthDate : Date
+department : String
+getDetails() : String
Java™ Module 6, slide 6 of 43Copyrig
C d Manager
";
ls() {...}
ends Employee {nt;
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
lass Diagrams for EmployeeanUsing Inheritance
public class Employee { public String name = " public double salary; public Date birthDate;
public String getDetai}
public class Manager ext public String departme}
Manager
+department : String
Employee
+name : String = ""
+salary : double
+birthDate : Date
+getDetails() : String
Java™ Module 6, slide 7 of 43Copyrig
ss, it is called
le inheritance
s>] {
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Single Inheritance
• When a class inherits from only one clasingle inheritance.
• Interfaces provide the benefits of multipwithout drawbacks.
• Syntax of a Java class is as follows:<modifier> class <name> [extends <superclas<declaration>*
}
Java™ Module 6, slide 8 of 43Copyrig
cretary
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Single Inheritance
Manager
+department : String = ""
Employee
+name : String = ""
+salary : double
+birthDate : Date
Director
+carAllowance : double
Engineer Se
+getDetails() : String
+increaseAllowance()
Java™ Module 6, slide 9 of 43Copyrig
Ac s are listed here.
Mo ass Universe
pri
def
pro
pub Yes
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Access Control
cess modifiers on class member declaration
difier Same Class Same Package Subcl
vate Yes
ault Yes Yes
tected Yes Yes Yes
lic Yes Yes Yes
Java™ Module 6, slide 10 of 43Copyrig
ed from a
fferent but with the
1.
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Overriding Methods
• A subclass can modify behavior inheritparent class.
• A subclass can create a method with difunctionality than the parent’s methodsame:• Name• Return type1
• Argument list
In J2SE version 5, the return type can be a subclass of the overridden return type.
Java™ Module 6, slide 11 of 43Copyrig
12345678910
123456789
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Overriding Methods
public class Employee {protected String name;protected double salary;protected Date birthDate;
public String getDetails() {return “Name: “ + name + “\n” +
“Salary: “ + salary;}
}
public class Manager extends Employee {protected String department;
public String getDetails() {return “Name: “ + name + “\n” +
“Salary: “ + salary + "\n" +“Manager of: “ + department;
}}
Java™ Module 6, slide 12 of 43Copyrig
e Less
123
123
12345678
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Overridden Methods Cannot BAccessible
public class Parent {public void doSomething() {}
}
public class Child extends Parent {private void doSomething() {} // illegal
}
public class UseBoth {public void doOtherThing() {Parent p1 = new Parent();Parent p2 = new Child();p1.doSomething();p2.doSomething();
}}
Java™ Module 6, slide 13 of 43Copyrig
ods
A s ethod using thesup
refer to its
the members ofthods.the superclass;
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Invoking Overridden Meth
ubclass method may invoke a superclass mer keyword:
• The keyword super is used in a class tosuperclass.
• The keyword super is used to refer tosuperclass, both data attributes and me
• Behavior invoked does not have to be init can be further up in the hierarchy.
Java™ Module 6, slide 14 of 43Copyrig
ods
123456789
123456789
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Invoking Overridden Meth
public class Employee {private String name;private double salary;private Date birthDate;
public String getDetails() {return "Name: " + name + "\nSalary: " + salary;
}}
public class Manager extends Employee {private String department;
public String getDetails() {// call parent methodreturn super.getDetails()
+ “\nDepartment: " + department;}
}
Java™ Module 6, slide 15 of 43Copyrig
y differentas access to
of different
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Polymorphism
• Polymorphism is the ability to have manforms; for example, the Manager class hmethods from Employee class.
• An object has only one form.• A reference variable can refer to objects
forms.
Java™ Module 6, slide 16 of 43Copyrig
Empl
// e.de// t// e
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Polymorphism
oyee e = new Manager(); // legal
illegal attempt to assign Manager attributepartment = "Sales";he variable is declared as an Employee type,ven though the Manager object has that attribute
Java™ Module 6, slide 17 of 43Copyrig
n
d as follows:
vocations have
of the declared has a method
based on theManager classtails method.
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Virtual Method Invocatio
• Virtual method invocation is performeEmployee e = new Manager();e.getDetails();
• Compile-time type and runtime type inthe following characteristics:• The method name must be a member
variable type; in this case Employeecalled getDetails.
• The method implementation used isruntime object’s type; in this case thehas an implementation of the getDe
Java™ Module 6, slide 18 of 43Copyrig
ns
ss type areple:
ss types aremple:
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Heterogeneous Collectio
• Collections of objects with the same clacalled homogeneous collections. For examMyDate[] dates = new MyDate[2];dates[0] = new MyDate(22, 12, 1964);dates[1] = new MyDate(22, 7, 1964);
• Collections of objects with different clacalled heterogeneous collections. For exaEmployee [] staff = new Employee[1024];staff[0] = new Manager();staff[1] = new Employee();staff[2] = new Engineer();
Java™ Module 6, slide 19 of 43Copyrig
Bec ing is valid:
publpu
}}
// MTaxSManTaxR
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Polymorphic Arguments
ause a Manager is an Employee, the follow
ic class TaxService {blic TaxRate findTaxRate(Employee e) {// calculate the employee’s tax rate
eanwhile, elsewhere in the application classervice taxSvc = new TaxService();ager m = new Manager();ate t = taxSvc.findTaxRate(m);
Java™ Module 6, slide 20 of 43Copyrig
or
publpublpubl----
publif
}
}
}}
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The instanceofOperat
ic class Employee extends Objectic class Manager extends Employeeic class Engineer extends Employee------------------------------------
ic void doSomething(Employee e) { ( e instanceof Manager ) {// Process a Managerelse if ( e instanceof Engineer ) {// Process an Engineerelse {// Process any other type of Employee
Java™ Module 6, slide 21 of 43Copyrig
”
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Casting Objects
public void doSomething(Employee e) {if ( e instanceof Manager ) {Manager m = (Manager) e;System.out.println(“This is the manager of
+ m.getDepartment());}// rest of operation
}
Java™ Module 6, slide 22 of 43Copyrig
bject.y casting.wing
ne implicitly.s and checked
when runtime
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Casting Objects
• Use instanceof to test the type of an o• Restore full functionality of an object b• Check for proper casting using the follo
guidelines:• Casts upward in the hierarchy are do• Downward casts must be to a subclas
by the compiler.• The object type is checked at runtime
errors can occur.
Java™ Module 6, slide 23 of 43Copyrig
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Overloading Methods
• Use overloading as follows:public void println(int i)public void println(float f)public void println(String s)
• Argument lists must differ.• Return types can be different.
Java™ Module 6, slide 24 of 43Copyrig
ments
it multiple
array. For
););
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Methods Using Variable Argu
• Methods using variable arguments permnumber of arguments in methods.For example:public class Statistics {public float average(int... nums) {int sum = 0;for ( int x : nums ) {sum += x;
}return ((float) sum) / nums.length;
}}
• The vararg parameter is treated as anexample:float gradePointAverage = stats.average(4, 3, 4float averageAge = stats.average(24, 32, 27, 18
Java™ Module 6, slide 25 of 43Copyrig
rs
verloaded.
e DoB)
irst line of a
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Overloading Constructo
• As with methods, constructors can be oAn example is:public Employee(String name, double salary, Datpublic Employee(String name, double salary)public Employee(String name, Date DoB)
• Argument lists must differ.• You can use the this reference at the f
constructor to call another constructor.
Java™ Module 6, slide 26 of 43Copyrig
rs
12 0;34567 DoB) {8910111213141516171819
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Overloading Constructo
public class Employee { private static final double BASE_SALARY = 15000.0 private String name; private double salary; private Date birthDate;
public Employee(String name, double salary, Date this.name = name; this.salary = salary; this.birthDate = DoB; }public Employee(String name, double salary) {
this(name, salary, null); } public Employee(String name, Date DoB) { this(name, BASE_SALARY, DoB); }// more Employee code...
}
Java™ Module 6, slide 27 of 43Copyrig
ited
iables from the
ctor from the
ors.
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Constructors Are Not Inher
• A subclass inherits all methods and varsuperclass (parent class).
• A subclass does not inherit the construsuperclass.
• Two ways to include a constructor are:• Use the default constructor.• Write one or more explicit construct
Java™ Module 6, slide 28 of 43Copyrig
uctors
st place a call tor.or by theper.structor, thenper() that callshich could be
s, but does noten a compiler
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Invoking Parent Class Constr
• To invoke a parent constructor, you musuper in the first line of the constructo
• You can call a specific parent constructarguments that you use in the call to su
• If no this or super call is used in a conthe compiler adds an implicit call to suthe parent no argument constructor (wthe default constructor).If the parent class defines constructorprovide a no-argument constructor, therror message is issued.
Java™ Module 6, slide 29 of 43Copyrig
uctors
1234 dept) {56789101112 s: no super()13141516
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Invoking Parent Class Constr
public class Manager extends Employee {private String department;
public Manager(String name, double salary, Stringsuper(name, salary);department = dept;
}public Manager(String name, String dept) {super(name);department = dept;
}public Manager(String dept) { // This code faildepartment = dept;
}//more Manager code...
}
Java™ Module 6, slide 30 of 43Copyrig
C ts: A Slight
Me occurs.
Ins s recursively:
then skip to
t super call,
initializers.ructor.
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
onstructing and Initializing ObjecReprise
mory is allocated and default initialization
tance variable initialization uses these step
1. Bind constructor parameters.2. If explicit this(), call recursively, and
Step 5.3. Call recursively the implicit or explici
except for Object.4. Execute the explicit instance variable5. Execute the body of the current const
Sun Services
Constructor and InitializationExamples
1 public class Object {2 public Object() {}3 }
1 public class Employee extends Object {2 private String name;3 private double salary = 15000.00;4 private Date birthDate;56 public Employee(String n, Date DoB) {7 // implicit super();8 name = n;9 birthDate = DoB;10 }11 public Employee(String n) {12 this(n, null);13 }14 }
1 public class Manager extends Employee {2 private String department;34 public Manager(String n, String d) {5 super(n);6 department = d;7 }8 }
Java™ Programming Language Module 6, slide 31 of 43Copyright 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Java™ Module 6, slide 32 of 43Copyrig
xamples
0 Ba 0. 0.1 C 1. 1. 1. ull
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Constructor and Initialization E
sic initialization1 Allocate memory for the completeManager object2 Initialize all instance variables to their default values (0 ornull)
all constructor:Manager("Joe Smith", "Sales")1 Bind constructor parameters:n="Joe Smith", d="Sales"2 No explicitthis() call3 Callsuper(n) forEmployee(String)1.3.1 Bind constructor parameters:n="Joe Smith"1.3.2 Callthis(n, null) forEmployee(String, Date) 1.3.2.1 Bind constructor parameters:n="Joe Smith", DoB=n 1.3.2.2 No explicitthis() call 1.3.2.3 Callsuper() forObject() 1.3.2.3.1 No binding necessary 1.3.2.3.2 Nothis() call 1.3.2.3.3 Nosuper() call(Object is the root) 1.3.2.3.4 No explicit variable initialization forObject 1.3.2.3.5 No method body to call
Java™ Module 6, slide 33 of 43Copyrig
xamples
0; 1. 1.
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Constructor and Initialization E
1.3.2.4 Initialize explicit Employee variables:salary=15000.0 1.3.2.5 Execute body:name="Joe Smith"; date=null;1.3.3 - 1.3.4 Steps skipped1.3.5 Execute body: No body inEmployee(String)4 No explicit initializers forManager5 Execute body:department="Sales"
Java™ Module 6, slide 34 of 43Copyrig
s in Java.ause implies
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The ObjectClass
• The Object class is the root of all classe• A class declaration with no extends cl
extends Object. For example:public class Employee { ...}
is equivalent to:public class Employee extends Object { ...}
• Two important methods are:• equals
• toString
Java™ Module 6, slide 35 of 43Copyrig
rences arehe same object).ts are equal but
als method
ethod touality.emethod if you
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The equalsMethod
• The == operator determines if two refeidentical to each other (that is, refer to t
• The equalsmethod determines if objecnot necessarily identical.
• The Object implementation of the equuses the == operator.
• User classes can override the equals mimplement a domain-specific test for eq
• Note: You should override thehashCodoverride the equals method.
Java™ Module 6, slide 36 of 43Copyrig
12345678910
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
An equalsExample
public class MyDate { private int day; private int month; private int year;
public MyDate(int day, int month, int year) { this.day = day; this.month = month; this.year = year; }
Java™ Module 6, slide 37 of 43Copyrig
1112131415161718192021222324252627
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
An equalsExample
public boolean equals(Object o) {boolean result = false;if ( (o != null) && (o instanceof MyDate) ) {MyDate d = (MyDate) o;if ( (day == d.day) && (month == d.month)
&& (year == d.year) ) {result = true;
}}return result;
}
public int hashCode() {return (day ^ month ^ year);
}}
Java™ Module 6, slide 38 of 43Copyrig
1234567 e2");89 date2");10111213 ;1415 e2");16
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
An equalsExample
class TestEquals {public static void main(String[] args) {
MyDate date1 = new MyDate(14, 3, 1976); MyDate date2 = new MyDate(14, 3, 1976);
if ( date1 == date2 ) { System.out.println("date1 is identical to dat } else { System.out.println("date1 is not identical to }
if ( date1.equals(date2) ) { System.out.println("date1 is equal to date2") } else { System.out.println("date1 is not equal to dat }
Java™ Module 6, slide 39 of 43Copyrig
171819202122 e2");2324 date2");252627
Th
datedateset date
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
An equalsExample
System.out.println("set date2 = date1;"); date2 = date1;
if ( date1 == date2 ) { System.out.println("date1 is identical to dat } else { System.out.println("date1 is not identical to } }}
is example generates the following output:
1 is not identical to date21 is equal to date2date2 = date1;1 is identical to date2
Java™ Module 6, slide 40 of 43Copyrig
Th acteristics:
ing.ation.ation about a
c method to
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The toStringMethod
e toString method has the following char
• This method converts an object to a Str• Use this method during string concaten• Override this method to provide inform
user-defined object in readable format.• Use the wrapper class’s toString stati
convert primitive types to a String.
Java™ Module 6, slide 41 of 43Copyrig
Lo
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Wrapper Classes
ok at primitive data elements as objects.
Primitive Data Type Wrapper Class
boolean Boolean
byte Byte
char Character
short Short
int Integer
long Long
float Float
double Double
Java™ Module 6, slide 42 of 43Copyrig
An
int Inte oxingint
Oth
int int
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Wrapper Classes
example of a wrapper class is:
pInt = 420;ger wInt = new Integer(pInt); // this is called bp2 = wInt.intValue(); // this is called unboxing
er methods are:
x = Integer.valueOf(str).intValue();x = Integer.parseInt(str);
Java™ Module 6, slide 43 of 43Copyrig
pes
Au
ject equivalent
xingg
n dealing with
metic
ng
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Autoboxing of Primitive Ty
toboxing has the following description:
• Conversion of primitive types to the ob• Wrapper classes not always needed• Example:
int pInt = 420;Integer wInt = pInt; // this is called autoboint p2 = wInt; // this is called autounboxin
• Language feature used most often whecollections
• Wrapped primitives also usable in arithexpressions
• Performance loss when using autoboxi
Sun
Java™ Programmi
res
Services
ng Language
Module 7
Advanced Class Featu
Java™ Module 7, slide 2 of 44Copyrig
itializersbles
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Objectives
• Create static variables, methods, and in• Create final classes, methods, and varia• Create and use enumerated types• Use the static import statement• Create abstract classes and methods• Create and use an interface
Java™ Module 7, slide 3 of 44Copyrig
by all instances
om being
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Relevance
• How can you create a constant?• How can you declare data that is shared
of a given class?• How can you keep a class or method fr
subclassed or overridden?
Java™ Module 7, slide 4 of 44Copyrig
ier on variables,
bute or methodather than any
ass members,
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The staticKeyword
• Thestatickeyword is used as a modifmethods, and nested classes.
• The static keyword declares the attriis associated with the class as a whole rparticular instance of that class.
• Thus static members are often called clsuch as class attributes or class methods.
Java™ Module 7, slide 5 of 44Copyrig
Cla s of a class:
123456789
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Class Attributes
ss attributes are shared among all instance
public class Count {private int serialNumber;public static int counter = 0;
public Count() {counter++;serialNumber = counter;
}}
c1 : Count
Count
serialNumber=1
-serialNumber : int
+counter : int = 0
c2 : Count
serialNumber=2
«instanceOf»«instanceOf»
Java™ Module 7, slide 6 of 44Copyrig
If t
12345678
it c out an instance:
12345
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Class Attributes
he static member is public:
public class Count1 {private int serialNumber;public static int counter = 0;
public Count1() { counter++; serialNumber = counter; }}
an be accessed from outside the class with
public class OtherClass { public void incrementNumber() {
Count1.counter++; }}
Java™ Module 7, slide 7 of 44Copyrig
You
12345678910111213
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Class Methods
can create static methods:
public class Count2 { private int serialNumber; private static int counter = 0;
public static int getTotalCount() { return counter; }
public Count2() {counter++;
serialNumber = counter; }}
Java™ Module 7, slide 8 of 44Copyrig
You instance of thecla
123456789
Th
NumbNumb
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Class Methods
can invoke static methods without anyss to which it belongs:
public class TestCounter { public static void main(String[] args) { System.out.println("Number of counter is " + Count2.getTotalCount()); Count2 counter = new Count2(); System.out.println("Number of counter is " + Count2.getTotalCount()); }}
e output of the TestCounter program is:
er of counter is 0er of counter is 1
Java™ Module 7, slide 9 of 44Copyrig
Sta es:
12345678
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Class Methods
tic methods cannot access instance variabl
public class Count3 { private int serialNumber; private static int counter = 0;
public static int getSerialNumber() { return serialNumber; // COMPILER ERROR! }}
Java™ Module 7, slide 10 of 44Copyrig
that does not
hen the class is
ze static (class)
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Static Initializers
• A class can contain code in a static blockexist within a method body.
• Static block code executes once only, wloaded.
• Usually, a static block is used to initialiattributes.
Java™ Module 7, slide 11 of 44Copyrig
1234 ter").intValue();56
123 );45
Th is:
javacoun
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Static Initializers
public class Count4 { public static int counter;static {
counter = Integer.getInteger("myApp.Count4.coun}
}
public class TestStaticInit { public static void main(String[] args) { System.out.println("counter = "+ Count4.counter }}
e output of the TestStaticInit program
-DmyApp.Count4.counter=47 TestStaticInitter = 47
Java™ Module 7, slide 12 of 44Copyrig
, but thatthe declaration;
t be set in every
be set in the
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The finalKeyword
• You cannot subclass a final class.• You cannot override a final method.• A final variable is a constant.• You can set a final variable once only
assignment can occur independently ofthis is called a blank final variable.• A blank final instance attribute mus
constructor.• A blank final method variable must
method body before being used.
Java™ Module 7, slide 13 of 44Copyrig
Co
publpr 3.2;..
}
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Final Variables
nstants are static final variables.
ic class Bank {ivate static final double DEFAULT_INTEREST_RATE = . // more declarations
Java™ Module 7, slide 14 of 44Copyrig
12345678910111213141516171819
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Blank Final Variables
public class Customer {
private final long customerID;
public Customer() {customerID = createID();
}
public long getID() {return customerID;
}
private long createID() {return ... // generate new ID
}
// more declarations
}
Java™ Module 7, slide 15 of 44Copyrig
Idiom
En gramming.1234567891011121314151617
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Old-Style Enumerated Type
umerated types are a common idiom in pro0
package cards.domain;
public class PlayingCard {
// pseudo enumerated type public static final int SUIT_SPADES = 0; public static final int SUIT_HEARTS = 1; public static final int SUIT_CLUBS = 2; public static final int SUIT_DIAMONDS = 3;
private int suit; private int rank;
public PlayingCard(int suit, int rank) { this.suit = suit; this.rank = rank; }
Java™ Module 7, slide 16 of 44Copyrig
Idiom2223242526272829303132333435363738394041
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Old-Style Enumerated Type} public String getSuitName() { String name = ““; switch ( suit ) { case SUIT_SPADES: name = “Spades”; break; case SUIT_HEARTS: name = “Hearts”; break; case SUIT_CLUBS: name = “Clubs”; break; case SUIT_DIAMONDS: name = “Diamonds”; break; default: System.err.println(“Invalid suit.”); } return name; }
Java™ Module 7, slide 17 of 44Copyrig
Idiom
Old123456789 ;10 ank()11 ());1213 uit.1415 ank()16 ());1718
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Old-Style Enumerated Type
-style idiom is not type-safe:0
package cards.tests;
import cards.domain.PlayingCard;
public class TestPlayingCard { public static void main(String[] args) {
PlayingCard card1 = new PlayingCard(PlayingCard.SUIT_SPADES, 2) System.out.println(“card1 is the “ + card1.getR + “ of “ + card1.getSuitName
// You can create a playing card with a bogus s PlayingCard card2 = new PlayingCard(47, 2); System.out.println(“card2 is the “ + card2.getR + “ of “ + card2.getSuitName }}
Java™ Module 7, slide 18 of 44Copyrig
Idiom
Th lems:
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Old-Style Enumerated Type
is enumerated type idiom has several prob
• Not type-safe• No namespace• Brittle character• Uninformative printed values
Java™ Module 7, slide 19 of 44Copyrig
pe
No es:12345678
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The New Enumerated Ty
w you can create type-safe enumerated typ0
package cards.domain;
public enum Suit { SPADES, HEARTS, CLUBS, DIAMONDS}
Java™ Module 7, slide 20 of 44Copyrig
pe
Us123456789101112131415
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The New Enumerated Ty
ing enumerated types is easy:0
package cards.domain;
public class PlayingCard {
private Suit suit; private int rank;
public PlayingCard(Suit suit, int rank) { this.suit = suit; this.rank = rank; }
public Suit getSuit() { return suit; }
Java™ Module 7, slide 21 of 44Copyrig
e161718192021222324252627282930313233343536
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The New Enumerated Typ public String getSuitName() { String name = ““; switch ( suit ) { case SPADES: name = “Spades”; break; case HEARTS: name = “Hearts”; break; case CLUBS: name = “Clubs”; break; case DIAMONDS: name = “Diamonds”; break; default: // No need for error checking as the Suit // enum is finite. } return name; }
Java™ Module 7, slide 22 of 44Copyrig
pe
En1234567891011 ank()12 ());1314151617
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The New Enumerated Ty
umerated types are type-safe:0
package cards.tests;
import cards.domain.PlayingCard;import cards.domain.Suit;
public class TestPlayingCard { public static void main(String[] args) {
PlayingCard card1 = new PlayingCard(Suit.SPADES, 2); System.out.println(“card1 is the “ + card1.getR + “ of “ + card1.getSuitName
// PlayingCard card2 = new PlayingCard(47, 2); // This will not compile. }}
Java™ Module 7, slide 23 of 44Copyrig
pes
En thods:123456789101112131415161718
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Advanced Enumerated Ty
umerated types can have attributes and me0
package cards.domain;
public enum Suit { SPADES (“Spades”), HEARTS (“Hearts”), CLUBS (“Clubs”), DIAMONDS (“Diamonds”);
private final String name;
private Suit(String name) { this.name = name; }
public String getName() { return name; }}
Java™ Module 7, slide 24 of 44Copyrig
pes
Pu ssible:1234567891011 ank()12 etName());1314 , 2);151617
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Advanced Enumerated Ty
blic methods on enumerated types are acce0
package cards.tests;
import cards.domain.PlayingCard;import cards.domain.Suit;
public class TestPlayingCard { public static void main(String[] args) {
PlayingCard card1 = new PlayingCard(Suit.SPADES, 2); System.out.println(“card1 is the “ + card1.getR + “ of “ + card1.getSuit().g
// NewPlayingCard card2 = new NewPlayingCard(47 // This will not compile. }}
Java™ Module 7, slide 25 of 44Copyrig
ers from a class:er_name>;
idually or
nstants:;
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Static Imports
• A static import imports the static membimport static <pkg_list>.<class_name>.<membORimport static <pkg_list>.<class_name>.*;
• A static import imports members indivcollectively:import static cards.domain.Suit.SPADES;ORimport static cards.domain.Suit.*;
• There is no need to qualify the static coPlayingCard card1 = new PlayingCard(SPADES, 2)
• Use this feature sparingly.
Java™ Module 7, slide 26 of 44Copyrig
An12345678910 ank()11 etName());1213 , 2);141516
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Static Imports
example of a static import is:0
package cards.tests;
import cards.domain.PlayingCard;import static cards.domain.Suit.*;
public class TestPlayingCard { public static void main(String[] args) {
PlayingCard card1 = new PlayingCard(SPADES, 2); System.out.println(“card1 is the “ + card1.getR + “ of “ + card1.getSuit().g
// NewPlayingCard card2 = new NewPlayingCard(47 // This will not compile. }}
Java™ Module 7, slide 27 of 44Copyrig
Th this:
hicle
RiverBarge
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Abstract Classes
e design of the Shipping system looks like
Ve
Truck
Companyfleet
0..*
shipping
domainShippingMain «Uses»
FuelNeedsReport «Uses»
reports
Java™ Module 7, slide 28 of 44Copyrig
Fle
12345 s6789101112 ;131415
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Abstract Classes
et initialization code is shown here:
public class ShippingMain {public static void main(String[] args) {Company c = new Company();
// populate the company with a fleet of vehiclec.addVehicle( new Truck(10000.0) );c.addVehicle( new Truck(15000.0) );c.addVehicle( new RiverBarge(500000.0) );c.addVehicle( new Truck(9500.0) );c.addVehicle( new RiverBarge(750000.0) );
FuelNeedsReport report = new FuelNeedsReport(c)report.generateText(System.out);
}}
Java™ Module 7, slide 29 of 44Copyrig
12345678910111213 + ) {1415
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Abstract Classes
public class FuelNeedsReport {private Company company;
public FuelNeedsReport(Company company) {this.company = company;
}
public void generateText(PrintStream output) {Vehicle1 v;double fuel;double total_fuel = 0.0;
for ( int i = 0; i < company.getFleetSize(); i+v = company.getVehicle(i);
Java™ Module 7, slide 30 of 44Copyrig
1617 fficency();1819 eeds "20212223 uel + " liters.");2425
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Abstract Classes
// Calculate the fuel needed for this tripfuel = v.calcTripDistance() / v.calcFuelE
output.println("Vehicle " + v.getName() + " n+ fuel + " liters of fuel.");
total_fuel += fuel;}output.println("Total fuel needs is " + total_f
}}
Java™ Module 7, slide 31 of 44Copyrig
An hich the fullim by the concretesub
e
() : double
: double
: double)
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Solution
abstract class models a class of objects in wplementation is not known but is suppliedclasses.
RiverBarg
Vehicle
+calcFuelEfficiency() : double
+calcTripDistance() : double
Truck
+calcFuelEfficiency() : double
+calcTripDistance() : double
+Truck(maxLoad : double)
{abstract}
«constructors»
«methods»+calcFuelEfficiency
+calcTripDistance()
+RiverBarge(maxLoad
«constructors»
«methods»
Java™ Module 7, slide 32 of 44Copyrig
Th
1234
Th n:
1234 a given load */567 ay */89
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Solution
e declaration of the Vehicle class is:
public abstract class Vehicle {public abstract double calcFuelEfficiency();public abstract double calcTripDistance();
}
e Truck class must create an implementatio
public class Truck extends Vehicle {public Truck(double maxLoad) {...}
public double calcFuelEfficiency() { /* calculate the fuel consumption of a truck at } public double calcTripDistance() { /* calculate the distance of this trip on highw }}
Java™ Module 7, slide 33 of 44Copyrig
Lik nim
1234 ge */567 e river-ways */89
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Solution
ewise, the RiverBarge class must create aplementation:
public class RiverBarge extends Vehicle {public RiverBarge(double maxLoad) {...}
public double calcFuelEfficiency() { /* calculate the fuel efficiency of a river bar } public double calcTripDistance() { /* calculate the distance of this trip along th }}
Java™ Module 7, slide 34 of 44Copyrig
lient code and.such a contractentation.
the same
interfaces.
s>]face>]* ] {
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Interfaces
• A public interface is a contract between cthe class that implements that interface
• A Java interface is a formal declaration ofin which all methods contain no implem
• Many unrelated classes can implementinterface.
• A class can implement many unrelated• Syntax of a Java class is as follows:
<modifier> class <name> [extends <superclas[implements <interface> [,<inter
<member_declaration>*}
Java™ Module 7, slide 35 of 44Copyrig
publpupupu
}
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Flyer Example
ic interface Flyer {blic void takeOff();blic void land();blic void fly();
+takeOff()
+land()
+fly()
«interface»
Flyer
+takeOff()
+land()
+fly()
Airplane
Java™ Module 7, slide 36 of 44Copyrig
publpu
}pu
}pu
}}
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Flyer Example
ic class Airplane implements Flyer {blic void takeOff() {// accelerate until lift-off// raise landing gear
blic void land() {// lower landing gear// decelerate and lower flaps until touch-down// apply brakes
blic void fly() {// keep those engines running
Java™ Module 7, slide 37 of 44Copyrig
)
an
ding()
et()
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Flyer Example
+takeOff()
+land()
+fly()
«interface»
Flyer
+takeOff()
+land()
+fly()
Airplane
+takeOff()
+land()
+fly()
Bird
+takeOff(
+land()
+fly()
Superm
+buildNest()
+layEggs()
+leapBuil
+stopBull
Java™ Module 7, slide 38 of 44Copyrig
Kryptonian
eOff()
d()
()
perman
pBuilding()
pBullet()
()
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Flyer Example
Vehicle
Animal
+eat()
+takeOff()
+land()
+fly()
«interface»
Flyer
+takeOff()
+land()
+fly()
Airplane
+takeOff()
+land()
+fly()
Bird
+tak
+lan
+fly
Su
+buildNest()
+layEggs()
+lea
+sto
+eat() +eat
Java™ Module 7, slide 39 of 44Copyrig
publpu */ }pu */ }pu */ }pu */ }pu */ }pu */ }
}
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Flyer Example
ic class Bird extends Animal implements Flyer {blic void takeOff() { /* take-off implementationblic void land() { /* landing implementationblic void fly() { /* fly implementationblic void buildNest() { /* nest building behaviorblic void layEggs() { /* egg laying behaviorblic void eat() { /* override eating behavior
Java™ Module 7, slide 40 of 44Copyrig
Kryptonian
takeOff()
land()
fly()
Superman
leapBuilding()
stopBullet()
eat()
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Flyer Example
Vehicle
Animal
+eat()
+takeOff()
+land()
+fly()
«interface»
Flyer
+takeOff()
+land()
+fly()
Airplane
+takeOff()
+land()
+fly()
Bird
+
+
+
+buildNest()
+layEggs()
+
+
+eat() +
HelicopterSeaPlane
Java™ Module 7, slide 41 of 44Copyrig
publpu
}
pr
}}
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Flyer Example
ic class Airport {blic static void main(String[] args) {Airport metropolisAirport = new Airport();Helicopter copter = new Helicopter();SeaPlane sPlane = new SeaPlane();
metropolisAirport.givePermissionToLand(copter);metropolisAirport.givePermissionToLand(sPlane);
ivate void givePermissionToLand(Flyer f) {f.land();
Java™ Module 7, slide 42 of 44Copyrig
le
keOff()
nd()
y()
interface»
Flyer
ff()
)
lane
Helicopter
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Multiple Interface Examp
+ta
+la
+fl
«
+takeO
+land(
+fly()
Airp
+dock()
+cruise()
«interface»
Sailer
SeaPlane
+dock()
+cruise()
Vehicle
RiverBarge
+dock()
+cruise()
Java™ Module 7, slide 43 of 44Copyrig
le
publpu
}
pr
}}
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Multiple Interface Examp
ic class Harbor {blic static void main(String[] args) {Harbor bostonHarbor = new Harbor();RiverBarge barge = new RiverBarge();SeaPlane sPlane = new SeaPlane();
bostonHarbor.givePermissionToDock(barge);bostonHarbor.givePermissionToDock(sPlane);
ivate void givePermissionToDock(Sailer s) {s.dock();
Java™ Module 7, slide 44 of 44Copyrig
Int
sses are
interfacee classed classes
laring a class
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Uses of Interfaces
erface uses include the following:
• Declaring methods that one or more claexpected to implement
• Determining an object’s programming without revealing the actual body of th
• Capturing similarities between unrelatwithout forcing a class relationship
• Simulating multiple inheritance by decthat implements several interfaces
Sun
Java™ Programmi
ons
Services
ng Language
Module 8
Exceptions and Asserti
Java™ Module 8, slide 2 of 25Copyrig
ts
exceptions
iate uses of
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Objectives
• Define exceptions• Use try, catch, and finally statemen• Describe exception categories• Identify common exceptions• Develop programs to handle your own• Use assertions• Distinguish appropriate and inappropr
assertions• Enable assertions at runtime
Java™ Module 8, slide 3 of 25Copyrig
do you resolve
y your codeng, what might
pend CPU programs?
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Relevance
• In most programming languages, how runtime errors?
• If you make assumptions about the waworks, and those assumptions are wrohappen?
• Is it always necessary or desirable to expower testing assertions in production
Java™ Module 8, slide 4 of 25Copyrig
ns
ns – Illegaloundming here from code atn at all.
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Exceptions and Assertio
• Exceptions handle unexpected situatioargument, network failure, or file not f
• Assertions document and test programassumptions – This can never be negative
• Assertion tests can be removed entirelyruntime, so the code is not slowed dow
Java™ Module 8, slide 5 of 25Copyrig
orrect program
on class.ted as fatal or bugs are
Error class.
exceptions that
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Exceptions
• Conditions that can readily occur in a care checked exceptions.These are represented by the Excepti
• Severe problems that normally are treasituations that probably reflect programunchecked exceptions.Fatal situations are represented by theProbable bugs are represented by theRuntimeException class.
• The API documentation shows checkedcan be thrown from a method.
Java™ Module 8, slide 6 of 25Copyrig
123456789
javSum
javExce r input string: "two"
matException.java:48)
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Exception Example
public class AddArguments { public static void main(String args[]) { int sum = 0; for ( String arg : args ) { sum += Integer.parseInt(arg); } System.out.println("Sum = " + sum); }}
a AddArguments 1 2 3 4= 10
a AddArguments 1 two 3.0 4ption in thread "main" java.lang.NumberFormatException: Foat java.lang.NumberFormatException.forInputString(NumberForat java.lang.Integer.parseInt(Integer.java:447)at java.lang.Integer.parseInt(Integer.java:497)at AddArguments.main(AddArguments.java:5)
Java™ Module 8, slide 7 of 25Copyrig
nt
1234567891011 eger.");121314
javOne
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The try-catchStateme
public class AddArguments2 { public static void main(String args[]) {
try { int sum = 0;
for ( String arg : args ) {sum += Integer.parseInt(arg);
} System.out.println("Sum = " + sum);
} catch (NumberFormatException nfe) { System.err.println("One of the command-line "
+ "arguments is not an int}
}}
a AddArguments2 1 two 3.0 4of the command-line arguments is not an integer.
Java™ Module 8, slide 8 of 25Copyrig
nt
12345678 integer"9 uded in the sum.");1011121314
jav[two sum.[3.0 sum.Sum
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The try-catchStateme
public class AddArguments3 { public static void main(String args[]) { int sum = 0;
for ( String arg : args ) {try {sum += Integer.parseInt(arg);
} catch (NumberFormatException nfe) {System.err.println("[" + arg + "] is not an
+ " and will not be incl}
} System.out.println("Sum = " + sum); }}
a AddArguments3 1 two 3.0 4] is not an integer and will not be included in the] is not an integer and will not be included in the= 5
Java™ Module 8, slide 9 of 25Copyrig
nt
A t h clauses:
try //
} ca// wn
} ca// thrown
} ca//
}
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The try-catchStateme
ry-catch statement can use multiple catc
{ code that might throw one or more exceptions
tch (MyException e1) { code to execute if a MyException exception is thro
tch (MyOtherException e2) { code to execute if a MyOtherException exception is
tch (Exception e3) { code to execute if any other exception is thrown
Java™ Module 8, slide 10 of 25Copyrig
rent try-catchethod.thod and is not
ed abnormally.
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Call Stack Mechanism
• If an exception is not handled in the curblock, it is thrown to the caller of that m
• If the exception gets back to the main mehandled there, the program is terminat
Java™ Module 8, slide 11 of 25Copyrig
Th at alwaysexe
12345678
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The finallyClause
e finally clause defines a block of code thcutes.
try { startFaucet(); waterLawn();} catch (BrokenPipeException e) {
logProblem(e); } finally { stopFaucet();}
Java™ Module 8, slide 12 of 25Copyrig
icException
terException
rgumentException
ception
rflowError
oryError
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Exception Categories
Throwable
Error
Exception
RuntimeException
IOException
Arithmet
NullPoin
IllegalA
FileNotFoundEx
VirtualMachineError
AssertionError
StackOve
OutOfMem
EOFException
SQLException
Java™ Module 8, slide 13 of 25Copyrig
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Common Exceptions
• NullPointerException
• FileNotFoundException
• NumberFormatException
• ArithmeticException
• SecurityException
Java™ Module 8, slide 14 of 25Copyrig
le
Us
on by using the
on { ... }
Oth
eptions or
ptions.
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Handle or Declare Ru
e the handle or declare rule as follows:
• Handle the exception by using thetry-catch-finally block.
• Declare that the code causes an exceptithrows clause.void trouble() throws IOException { ... }void trouble() throws IOException, MyExcepti
er Principles
• You do not need to declare runtime excerrors.
• You can choose to handle runtime exce
Java™ Module 8, slide 15 of 25Copyrig
ptions
Th
by the
s thrown by the
Th
e overridden
by the
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Method Overriding and Exce
e overriding method can throw:
• No exceptions• One or more of the exceptions thrown
overridden method• One or more subclasses of the exception
overridden method
e overriding method cannot throw:
• Additional exceptions not thrown by thmethod
• Superclasses of the exceptions thrown overridden method
Java™ Module 8, slide 16 of 25Copyrig
tions
12345
12345
12 G345
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Method Overriding and Excep
public class TestA { public void methodA() throws IOException { // do some file manipulation }}
public class TestB1 extends TestA { public void methodA() throws EOFException {
// do some file manipulation}
}
public class TestB2 extends TestA { public void methodA() throws Exception { // WRON
// do some file manipulation}
}
Java™ Module 8, slide 17 of 25Copyrig
ions
1 ception {234 t port) {56789101112
Us the Exceptioncla n was made.
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Creating Your Own Except
public class ServerTimedOutException extends Ex private int port;
public ServerTimedOutException(String message, insuper(message);
this.port = port; }
public int getPort() { return port; }}
e the getMessage method, inherited from ss, to get the reason for which the exceptio
Java™ Module 8, slide 18 of 25Copyrig
eption
A m exception:
123456789 t connect",10 nect);1112
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Handling a User-Defined Exc
ethod can throw a user-defined, checked
public void connectMe(String serverName)throws ServerTimedOutException {
boolean successful; int portToConnect = 80;
successful = open(serverName, portToConnect);
if ( ! successful ) {throw new ServerTimedOutException("Could no portToCon
}}
Java™ Module 8, slide 19 of 25Copyrig
eption
An o captureuse
12345 alternative");6789 e() +10 e1.getPort());111213
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Handling a User-Defined Exc
other method can use a try-catch block tr-defined exceptions:
public void findServer() { try { connectMe(defaultServer); } catch (ServerTimedOutException e) { System.out.println("Server timed out, trying try { connectMe(alternativeServer); } catch (ServerTimedOutException e1) { System.out.println("Error: " + e1.getMessag " connecting to port " + } } }
Java™ Module 8, slide 20 of 25Copyrig
ssion> ;
false, then an
string and usedror message.
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Assertions
• Syntax of an assertion is:assert <boolean_expression> ;assert <boolean_expression> : <detail_expre
• If <boolean_expression> evaluatesAssertionError is thrown.
• The second argument is converted to aas descriptive text in the AssertionEr
Java™ Module 8, slide 21 of 25Copyrig
rtions
Us umptions andint
Ina
meters of a
eck that can
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Recommended Uses of Asse
e assertions to document and verify the assernal logic of a single method:
• Internal invariants• Control flow invariants• Postconditions and class invariants
ppropriate Uses of Assertions
• Do not use assertions to check the parapublic method.
• Do not use methods in the assertion chcause side-effects.
Java™ Module 8, slide 22 of 25Copyrig
Th
12345
Th
123456
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Internal Invariants
e problem is:
if (x > 0) {// do this
} else {// do that
}
e solution is:
if (x > 0) {// do this
} else {assert ( x == 0 );// do that, unless x is negative
}
Java™ Module 8, slide 23 of 25Copyrig
For
12345678910 d suit";1112
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Control Flow Invariants
example:
switch (suit) { case Suit.CLUBS: // ... break; case Suit.DIAMONDS: // ... break; case Suit.HEARTS: // ... break; case Suit.SPADES: // ... break; default: assert false : "Unknown playing car break;}
Java™ Module 8, slide 24 of 25Copyrig
riants
For
1234 empty stack");567 ement */ ;8910111213
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Postconditions and Class Inva
example:
public Object pop() { int size = this.getElementCount(); if (size == 0) { throw new RuntimeException("Attempt to pop from }
Object result = /* code to retrieve the popped el
// test the postconditionassert (this.getElementCount() == size - 1);
return result;}
Java™ Module 8, slide 25 of 25Copyrig
C Assertions
e runs as fast as
lt. Enables:
class, package,
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ontrolling Runtime Evaluation of
• If assertion checking is disabled, the codif the check was never there.
• Assertion checks are disabled by defauassertions with the following commandjava -enableassertions MyProgram
or:java -ea MyProgram
• Assertion checking can be controlled onand package hierarchy bases, see:docs/guide/language/assert.html
Sun
Java™ Programmi
ns
Services
ng Language
Module 9
Text-Based Applicatio
Java™ Module 9, slide 2 of 37Copyrig
ne arguments
rd inputd outputnd write filesns in the Java 2)
tionctions
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Objectives
• Write a program that uses command-liand system properties
• Write a program that reads from standa• Describe the C-type formatted input an• Write a program that can create, read, a• Describe the basic hierarchy of collectio
Software Development Kit (Java 2 SDK• Write a program that uses sets and lists• Write a program to iterate over a collec• Write a program that uses generic colle
Java™ Module 9, slide 3 of 37Copyrig
of a programnames or the
be coded to
collections (thatava technologyollections?ents of any
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Relevance
• It is often the case that certain elementsshould not be hard-coded, such as file name of a database. How can a programsupply these elements at runtime?
• Simple arrays are far too static for mostis, a fixed number of elements). What Jfeatures exist to support more flexible c
• Besides computation, what are key elemtext-based application?
Java™ Module 9, slide 4 of 37Copyrig
ts
se
he commandthe class name:
in the argsethod:
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Command-Line Argumen
• Any Java technology application can ucommand-line arguments.
• These string arguments are placed on tline to launch the Java interpreter, afterjava TestArgs arg1 arg2 "another arg"
• Each command-line argument is placedarray that is passed to the static main mpublic static void main(String[] args)
Java™ Module 9, slide 5 of 37Copyrig
s
1234 rgs[i] + "’");567
Ex
javargsargsargs
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Command-Line Argument
public class TestArgs { public static void main(String[] args) { for ( int i = 0; i < args.length; i++ ) { System.out.println("args[" + i + "] is ’" + a } }}
ample execution:
a TestArgs arg1 arg2 "another arg"[0] is ’arg1’[1] is ’arg2’[2] is ’another arg’
Java™ Module 9, slide 6 of 37Copyrig
laces the are
eturns a
ringoperty.perty.
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
System Properties
• System properties are a feature that repconcept of environment variables (whichplatform-specific).
• The System.getProperties method rProperties object.
• The getProperty method returns a Strepresenting the value of the named pr
• Use the -D option to include a new pro
Java™ Module 9, slide 7 of 37Copyrig
pping of names
Enumeration
ringoperty.s collection into
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The PropertiesClass
• ThePropertiesclass implements a mato values (a String to String map).
• The propertyNames method returns anof all property names.
• The getProperty method returns a Strepresenting the value of the named pr
• You can also read and write a propertiea file using load and store.
Java™ Module 9, slide 8 of 37Copyrig
12345678910 ent();11 ;1213 ");141516
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The PropertiesClass
import java.util.Properties;import java.util.Enumeration;
public class TestProperties { public static void main(String[] args) { Properties props = System.getProperties(); Enumeration propNames = props.propertyNames();
while ( propNames.hasMoreElements() ) { String propName = (String) propNames.nextElem String property = props.getProperty(propName) System.out.println("property ’" + propName
+ "’ is ’" + property + "’ } }}
Java™ Module 9, slide 9 of 37Copyrig
He
jav
He
propproppropproppropprop ms Inc.’proppropprop
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The PropertiesClass
re is an example test run of this program:
a -DmyProp=theValue TestProperties
re is the (partial) output:
erty ’java.version’ is ’1.5.0-rc’erty ’java.compiler’ is ’NONE’erty ’path.separator’ is ’:’erty ’file.separator’ is ’/’erty ’user.home’ is ’/home/basham’erty ’java.specification.vendor’ is ’Sun Microsysteerty ’user.language’ is ’en’erty ’user.name’ is ’basham’erty ’myProp’ is ’theValue’
Java™ Module 9, slide 10 of 37Copyrig
o write to
read from
o write to
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Console I/O
• The variable System.out enables you tstandard output.It is an object of type PrintStream.
• The variable System.in enables you tostandard input.It is an object of type InputStream.
• The variable System.err enables you tstandard error.It is an object of type PrintStream.
Java™ Module 9, slide 11 of 37Copyrig
ut
ent and a
t without a
verloaded fornt, long,ject, and
ect) methodsent.
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Writing to Standard Outp
• The println methods print the argumnewline character (\n).
• The print methods print the argumennewline character.
• The print and println methods are omost primitive types (boolean, char, ifloat, and double) and for char[], ObString.
• The print(Object) and println(Objcall the toString method on the argum
Java™ Module 9, slide 12 of 37Copyrig
put
123456789101112 +13 xit");
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Reading From Standard In
import java.io.*;
public class KeyboardInput {public static void main (String args[]) {String s;// Create a buffered reader to read// each line from the keyboard.InputStreamReader ir= new InputStreamReader(System.in);
BufferedReader in = new BufferedReader(ir);
System.out.println("Unix: Type ctrl-d to exit.""\nWindows: Type ctrl-z to e
Java™ Module 9, slide 13 of 37Copyrig
ut
1415 reen.161718192021222324 tions.25262728
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Reading From Standard Inp
try {// Read each input line and echo it to the scs = in.readLine();while ( s != null ) {System.out.println("Read: " + s);s = in.readLine();
}
// Close the buffered reader.in.close();
} catch (IOException e) { // Catch any IO excepe.printStackTrace();
}}
}
Java™ Module 9, slide 14 of 37Copyrig
t
y as follows
l);
this table.
Co
%s ling the
%d cimal value.
%f es scientific
%n .
%%
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Simple Formatted Outpu
• You can use the formatting functionalitout.printf(“name count\n”);String s = String.format(“%s %5d%n”, user, tota
• Common formatting codes are listed in
de Description
Formats the argument as a string, usually by caltoString method on the object.
%o %x Formats an integer, as a decimal, octal, or hexade
%g Formats a floating point number. The %g code usnotation.
Inserts a newline character to the string or stream
Inserts the % character to the string or stream.
Java™ Module 9, slide 15 of 37Copyrig
t
input function.ut streams as
m);
ue);
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Simple Formatted Inpu
• The Scanner API provides a formatted • A Scanner can be used with console inp
well as file or network streams.• You can read console input as follows:
1 import java.io.*;2 import java.util.Scanner;3 public class ScanTest {4 public static void main(String [] args) {5 Scanner s = new Scanner(System.in);6 String param = s.next();7 System.out.println("the param 1" + para8 int value = s.nextInt();9 System.out.println("second param" + val10 s.close();11 }12 }
Java™ Module 9, slide 16 of 37Copyrig
Th ollowing:
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Files and File I/O
e java.io package enables you to do the f
• Create File objects• Manipulate File objects• Read and write to file streams
Java™ Module 9, slide 17 of 37Copyrig
ect
Th
;
file.txt");
Dir e File classsup les in thedir
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Creating a New FileObj
e File class provides several utilities:
• File myFile;
• myFile = new File("myfile.txt")
• myFile = new File("MyDocs", "my
ectories are treated just like files in Java; thports methods for retrieving an array of fi
ectory, as follows:
File myDir = new File("MyDocs");myFile = new File(myDir, "myfile.txt");
Java™ Module 9, slide 18 of 37Copyrig
es
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The FileTests and Utiliti
• File information:String getName()String getPath()String getAbsolutePath()String getParent()long lastModified()long length()
• File modification:boolean renameTo(File newName)boolean delete()
• Directory utilities:boolean mkdir()String[] list()
Java™ Module 9, slide 19 of 37Copyrig
s
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The FileTests and Utilitie
• File tests:boolean exists()boolean canWrite()boolean canRead()boolean isFile()boolean isDirectory()boolean isAbsolute();
Java™ Module 9, slide 20 of 37Copyrig
aracters.e the readLine
haracters.e print and
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
File Stream I/O
• For file input:• Use the FileReader class to read ch• Use the BufferedReader class to us
method.• For file output:
• Use the FileWriter class to write c• Use the PrintWriter class to use th
println methods.
Java™ Module 9, slide 21 of 37Copyrig
A fi
12345678910111213
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
File Stream I/O
le input example is:
import java.io.*;public class ReadFile { public static void main (String[] args) { // Create file File file = new File(args[0]);
try { // Create a buffered reader
// to read each line from a file. BufferedReader in
= new BufferedReader(new FileReader(file)); String s;
Java™ Module 9, slide 22 of 37Copyrig
14 o the screen.1516171819202122232425 ;26272829303132
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
File Stream I/O
// Read each line from the file and echo it ts = in.readLine();
while ( s != null ) {System.out.println("Read: " + s);s = in.readLine();
}// Close the buffered readerin.close();
} catch (FileNotFoundException e1) {// If this file does not exist
System.err.println("File not found: " + file)
} catch (IOException e2) {// Catch any other IO exceptions.
e2.printStackTrace();}
}}
Java™ Module 9, slide 23 of 37Copyrig
123456789 from standard in.1011121314151617
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
File Output Example
import java.io.*;
public class WriteFile {public static void main (String[] args) {// Create fileFile file = new File(args[0]);
try {// Create a buffered reader to read each lineInputStreamReader isr= new InputStreamReader(System.in);
BufferedReader in = new BufferedReader(isr); // Create a print writer on this file. PrintWriter out = new PrintWriter(new FileWriter(file)); String s;
Java™ Module 9, slide 24 of 37Copyrig
1819202122 reen.2324252627 nt writer.282930313233343536
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
File Output Example
System.out.print("Enter file text. "); System.out.println("[Type ctrl-d to stop.]");
// Read each input line and echo it to the sc while ((s = in.readLine()) != null) { out.println(s); }
// Close the buffered reader and the file pri in.close(); out.close();
} catch (IOException e) { // Catch any IO exceptions. e.printStackTrace(); } }}
Java™ Module 9, slide 25 of 37Copyrig
g a group of
that group
lled elements; allowance ofmentationuplicates are
ates are
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The Collections API
• A collection is a single object representinobjects known as its elements.
• The Collections API contains interfacesobjects as one of the following:• Collection – A group of objects ca
any specific ordering (or lack of) andduplicates is specified by each imple
• Set – An unordered collection; no dpermitted
• List – An ordered collection; duplicpermitted
Java™ Module 9, slide 26 of 37Copyrig
st
Object)t
ject) intor
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Collections API
Collection«interface»
Set«interface»
List«interface»
HashSet
ArrayList LinkedLi
+add(element : Object) : boolean
+size() : int+remove(element : Object) : boolean
+isEmpty() : boolean+contains(element : Object) : boolean+iterator() : Iterator
+add(index : int, element :
+get(index : int) : Object+remove(index : int) : Objec
+set(index : int, element Ob+indexOf(element : Object) :+listIterator() : ListIterat
Java™ Module 9, slide 27 of 37Copyrig
1234567891011 dded12 dded131415
Th
[one
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
A SetExample
import java.util.*;
public class SetExample { public static void main(String[] args) { Set set = new HashSet(); set.add("one"); set.add("second"); set.add("3rd"); set.add(new Integer(4)); set.add(new Float(5.0F)); set.add("second"); // duplicate, not a set.add(new Integer(4)); // duplicate, not a System.out.println(set); }}
e output generated from this program is:
, second, 5.0, 3rd, 4]
Java™ Module 9, slide 28 of 37Copyrig
1234567891011 dded12 dded131415
Th
[one
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
A ListExample
import java.util.*
public class ListExample { public static void main(String[] args) { List list = new ArrayList(); list.add("one"); list.add("second"); list.add("3rd"); list.add(new Integer(4)); list.add(new Float(5.0F)); list.add("second"); // duplicate, is a list.add(new Integer(4)); // duplicate, is a System.out.println(list); }}
e output generated from this program is:
, second, 3rd, 4, 5.0, second, 4]
Java™ Module 9, slide 29 of 37Copyrig
n 1.1
Co ™) include:
interface. and supports
ap interface.n on the
ementsble.
heavy weight.
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Collections in JDK™ Versio
llections in the Java Development Kit (JDK
• The class Vector implements the List• The class Stack is a subclass of Vector
the push, pop, and peek methods.• The class Hashtable implements the M• The Enumeration interface is a variatio
Iterator interface.An enumeration is returned by the elmethod in Vector, Stack, and Hashta
• Classes are thread-safe, and therefore,• These classes also support generics.
Java™ Module 9, slide 30 of 37Copyrig
Ge
Be
Arralistint
Aft
Arralistint
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Generics
nerics are described as follows:
• Provides compile-time type safety• Eliminates the need for casts
fore Generics
yList list = new ArrayList();.add(0, new Integer(42));total = ((Integer)list.get(0)).intValue();
er Generics
yList<Integer> list = new ArrayList<Integer>();.add(0, new Integer(42));total = list.get(0).intValue();
Java™ Module 9, slide 31 of 37Copyrig
I
t<E>
E)
or<E>
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Generic Collections APCollection<E>
«interface»
Set<E>«interface»
List<E>«interface»
HashSet<E>
ArrayList<E> LinkedLis
+add(element : E) : boolean
+size() : int+remove(element : E) : boolean
+isEmpty() : boolean+contains(element : E) : boolean+iterator() : Iterator<E>
+add(index : int, element :
+get(index : int) : E+remove(index : int) : E
+set(index : int, element E)+indexOf(element : E) : int+listIterator() : ListIterat
Java™ Module 9, slide 32 of 37Copyrig
javaNote rations.Note
javaGene call to add(int,E)as a 1 wa
12345678
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Compiler Warnings
c GenericsWarning.java: GenericsWarning.java uses unchecked or unsafe ope: Recompile with -Xlint:unchecked for details.
c -Xlint:unchecked GenericsWarning.javaricsWarning.java:7: warning: [unchecked] unchecked member of the raw type java.util.ArrayListlist.add(0, new Integer(42)); ^rning
0
import java.util.*;public class GenericsWarning { public static void main(String[] args) { List list = new ArrayList(); list.add(0, new Integer(42)); int total = ((Integer)list.get(0)).intValue(); }}
Java™ Module 9, slide 33 of 37Copyrig
ry element in a
ned forwards (using the
List// aIterwhilSy
}
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Iterators
• Iteration is the process of retrieving evecollection.
• An Iterator of a Set is unordered.• A ListIterator of a List can be scan
(using the next method) or backwardsprevious method).
list = new ArrayList();dd some elementsator elements = list.iterator();e ( elements.hasNext() ) {stem.out.println(elements.next());
Java™ Module 9, slide 34 of 37Copyrig
rchy
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Iterator Interface Hiera
Iterator<E>«interface»
ListIterator<E>«interface»
+hasNext() : boolean+next() : E+remove()
+hasPrevious() : boolean+previous() : E+add(element : E)+set(element : E)
Java™ Module 9, slide 35 of 37Copyrig
Th racteristics:
Ite
loop. to go wrong.
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Enhanced forLoop
e enhanced for loop has the following cha
• Simplified iteration over collections• Much shorter, clearer, and safer• Effective for arrays• Simpler when using nested loops• Iterator disadvantages removed
rators are error prone:
• Iterator variables occur three times per• This provides the opportunity for code
Java™ Module 9, slide 36 of 37Copyrig
An
.hasNext() ; ){
:
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Enhanced forLoop
enhanced for loop can look like this:
• Using iterators:public void deleteAll(Collection<NameList> c){for ( Iterator<NameList> i = c.iterator() ; iNameList nl = i.next();nl.deleteItem();
}}
• Using enhanced for loop in collectionspublic void deleteAll(Collection<NameList> c){for ( NameList nl : c ){nl.deleteItem();
}}
Java™ Module 9, slide 37 of 37Copyrig
ps:
();
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Enhanced forLoop
• Using enhanced for loop in arrays:public int sum(int[] array){int result = 0;for ( int element : array ) {result += element;
}return result;
}
• Using enhanced for loop in nested looList<Subject> subjects=...;List<Teacher> teachers=...;List<Course> courseList = new ArrayList<Course>for ( Subject subj : subjects ) {for ( Teacher tchr : teachers ) {courseList.add(new Course(subj, tchr));
}}
Sun
Java™ Programmi
Services
ng Language
Module 10
Building Java GUIs
Java™ Module 10, slide 2 of 37Copyrig
AWT)package
, and layouttogether to
nd GridLayout layout
propriatelysted containers
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Objectives
• Describe the Abstract Window Toolkit (and its components
• Define the terms containers, componentsmanagers, and describe how they work build a GUI
• Use layout managers• Use the FlowLayout, BorderLayout, a
managers to achieve a desired dynamic• Add components to a container• Use the Frame and Panel containers ap• Describe how complex layouts with ne
work
Java™ Module 10, slide 3 of 37Copyrig
As guage, how isJav ser interface(GU
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Relevance
a platform-independent programming lana technology used to make the graphical uI) platform-independent?
Java™ Module 10, slide 4 of 37Copyrig
t
Th
d in all Java
or extended;
is displayed onlass Component
bclass ofs:
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Abstract Window Toolki
e AWT performs the following:
• Provides GUI components that are useapplets and applications
• Contains classes that can be composed classes can also be abstract
• Ensures that every GUI component thatthe screen is a subclass of the abstract cor MenuComponent
• Has Container, which is an abstract suComponent and includes two subclasse• Panel
• Window
Sun Services
The java.awtPackage
java.lang.Object
ButtonCanvasCheckboxChoiceContainerLabelListScrollbarTextComponent
BorderLayoutCardLayoutCheckboxGroupColorEventFontFlowLayoutFontMetricsGraphicsGridBagLayoutGridLayoutImageInsetsPointPolygonRectangleToolkitMenuComponentComponent
MenuBarMenuItem Menu -- PopupMenu
CheckboxMenuItem
TextAreaTextField
PanelWindowScrollPane
DialogFrame
Applet (java.applet package)
FileDialog
Exceptions – AWTException Errors – AWTError
java.awt.geom.Dimension2D
java.lang.Object
Dimension
Java™ Programming Language Module 10, slide 5 of 37Copyright 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Java™ Module 10, slide 6 of 37Copyrig
od.indow and
the display.nts that must
iner, such as a
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Containers
• Add components with the add() meth• The two main types of containers are W
Panel.• A Window is a free floating window on • A Panel is a container of GUI compone
exist in the context of some other contawindow or applet.
Java™ Module 10, slide 7 of 37Copyrig
s
n a container is
omponents by
etSize(), orthem in the
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Positioning Component
• The position and size of a component idetermined by a layout manager.
• You can control the size or position of cdisabling the layout manager.You must then use setLocation(), ssetBounds() on components to locatecontainer.
Java™ Module 10, slide 8 of 37Copyrig
Fra
(true) to
out managerhe default
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Frames
mes have the following characteristics:
• Are a subclass of Window• Have title and resizing corners• Are invisible initially; use setVisible
expose the frame• Have BorderLayout as the default lay• Use the setLayout method to change t
layout manager
Java™ Module 10, slide 9 of 37Copyrig
s
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The FrameExampleClas
import java.awt.*;
public class FrameExample { private Frame f; public FrameExample() { f = new Frame("Hello Out There!"); }
public void launchFrame() { f.setSize(170,170); f.setBackground(Color.blue); f.setVisible(true); }
public static void main(String args[]) { FrameExample guiWindow = new FrameExample(); guiWindow.launchFrame(); }}
Java™ Module 10, slide 10 of 37Copyrig
dows
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Example Frame
Solaris OS Microsoft Win
Java™ Module 10, slide 11 of 37Copyrig
.n layout
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Panels
• Panels provide a space for components• This enables subpanels to have their ow
manager.
Java™ Module 10, slide 12 of 37Copyrig
ss
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The FrameWithPanelCla
import java.awt.*;
public class FrameWithPanel { private Frame f;private Panel pan;
public FrameWithPanel(String title) { f = new Frame(title);
pan = new Panel();}
Java™ Module 10, slide 13 of 37Copyrig
s
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The FrameWithPanelClas
public void launchFrame() { f.setSize(200,200); f.setBackground(Color.blue); f.setLayout(null); // Use default layout
pan.setSize(100,100); pan.setBackground(Color.yellow); f.add(pan); f.setVisible(true); }
public static void main(String args[]) { FrameWithPanel guiWindow = new FrameWithPanel("Frame with Panel"); guiWindow.launchFrame(); }}
Java™ Module 10, slide 14 of 37Copyrig
indows
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Example Panel
Solaris OSMicrosoft W
Java™ Module 10, slide 15 of 37Copyrig
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Layout Managers
• FlowLayout
• BorderLayout
• GridLayout
• CardLayout
• GridBagLayout
Java™ Module 10, slide 16 of 37Copyrig
s
ut
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Default Layout Manager
Component
Container
Window
Frame Dialog
BorderLayout
Panel
Applet
FlowLayo
Java™ Module 10, slide 17 of 37Copyrig
ple
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Sun Services
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A Simple FlowLayoutExam
import java.awt.*;
public class LayoutExample { private Frame f; private Button b1; private Button b2;
public LayoutExample() { f = new Frame("GUI example"); b1 = new Button("Press Me"); b2 = new Button("Don’t press Me"); }
Java™ Module 10, slide 18 of 37Copyrig
ple
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A Simple FlowLayoutExam
public void launchFrame() { f.setLayout(new FlowLayout()); f.add(b1); f.add(b2); f.pack(); f.setVisible(true); }
public static void main(String args[]) { LayoutExample guiWindow = new LayoutExample(); guiWindow.launchFrame(); }
} // end of LayoutExample class
Java™ Module 10, slide 19 of 37Copyrig
dows
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Example of FlowLayout
Solaris OS Microsoft Win
Java™ Module 10, slide 20 of 37Copyrig
er
Th haracteristics:
class
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The FlowLayoutManag
e FlowLayout manager has the following c
• Forms the default layout for the Panel• Adds components from left to right• Alignment default is centered• Uses components’ preferred sizes• Uses the constructor to tune behavior
Java™ Module 10, slide 21 of 37Copyrig
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The FlowLayoutResizing
Solaris OS
After user orprogram resizes
Java™ Module 10, slide 22 of 37Copyrig
s
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The FlowExampleClas
import java.awt.*;
public class FlowExample { private Frame f; private Button button1; private Button button2; private Button button3;
public FlowExample() { f = new Frame("Flow Layout"); button1 = new Button("Ok"); button2 = new Button("Open"); button3 = new Button("Close"); }
Java™ Module 10, slide 23 of 37Copyrig
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The FlowExampleClass
public void launchFrame() { f.setLayout(new FlowLayout()); f.add(button1); f.add(button2); f.add(button3); f.setSize(100,100); f.setVisible(true); }
public static void main(String args[]) { FlowExample guiWindow = new FlowExample(); guiWindow.launchFrame(); }}
Java™ Module 10, slide 24 of 37Copyrig
ger
ult layout for
ns.
just
t vertically
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The BorderLayoutMana
• The BorderLayout manager is the defathe Frame class.
• Components are added to specific regio• The resizing behavior is as follows:
• North, South, and Center regions adhorizontally
• East, West, and Center regions adjus
Java™ Module 10, slide 25 of 37Copyrig
ayout
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Organization of the Border LComponents
North
South
Eas
t
Wes
t
Center
Java™ Module 10, slide 26 of 37Copyrig
ss
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The BorderExampleCla
import java.awt.*;
public class BorderExample { private Frame f; private Button bn, bs, bw, be, bc;
public BorderExample() { f = new Frame("Border Layout"); bn = new Button("B1"); bs = new Button("B2"); bw = new Button("B3"); be = new Button("B4"); bc = new Button("B5"); }
Java™ Module 10, slide 27 of 37Copyrig
s
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The BorderExampleClas
public void launchFrame() { f.add(bn, BorderLayout.NORTH); f.add(bs, BorderLayout.SOUTH); f.add(bw, BorderLayout.WEST); f.add(be, BorderLayout.EAST); f.add(bc, BorderLayout.CENTER); f.setSize(200,200); f.setVisible(true); }
public static void main(String args[]) { BorderExample guiWindow2 = new BorderExample(); guiWindow2.launchFrame(); }}
Java™ Module 10, slide 28 of 37Copyrig
t
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Example of BorderLayou
Solaris OS
After user orprogram resizes
Java™ Module 10, slide 29 of 37Copyrig
er
t, and from top
columns.
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The GridLayoutManag
• Components are added from left to righto bottom.
• All regions are sized equally.• The constructor specifies the rows and
Java™ Module 10, slide 30 of 37Copyrig
s
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The GridExampleClas
import java.awt.*;
public class GridExample { private Frame f; private Button b1, b2, b3, b4, b5, b6;
public GridExample() { f = new Frame("Grid Example"); b1 = new Button("1"); b2 = new Button("2"); b3 = new Button("3"); b4 = new Button("4"); b5 = new Button("5"); b6 = new Button("6"); }
Java™ Module 10, slide 31 of 37Copyrig
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The GridExampleClass
public void launchFrame() { f.setLayout (new GridLayout(3,2)); f.add(b1); f.add(b2); f.add(b3); f.add(b4); f.add(b5); f.add(b6);
f.pack(); f.setVisible(true); }
public static void main(String args[]) { GridExample grid = new GridExample(); grid.launchFrame(); }}
Java™ Module 10, slide 32 of 37Copyrig
ows
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Example of GridLayout
Solaris OS
Microsoft Wind
After user orprogram resizes
After user orprogram resizes
Java™ Module 10, slide 33 of 37Copyrig
Class
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The ComplexLayoutExample
import java.awt.*;
public class ComplexLayoutExample { private Frame f; private Panel p; private Button bw, bc; private Button bfile, bhelp;
public ComplexLayoutExample() { f = new Frame("GUI example 3"); bw = new Button("West"); bc = new Button("Work space region"); bfile = new Button("File"); bhelp = new Button("Help"); }
Java™ Module 10, slide 34 of 37Copyrig
lass
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The ComplexLayoutExampleC
public void launchFrame() { // Add bw and bc buttons in the frame border f.add(bw, BorderLayout.WEST); f.add(bc, BorderLayout.CENTER); // Create panel for the buttons in the north bo p = new Panel(); p.add(bfile); p.add(bhelp); f.add(p, BorderLayout.NORTH); // Pack the frame and make it visible f.pack(); f.setVisible(true); }
public static void main(String args[]) { ComplexLayoutExample gui = new ComplexLayoutExa gui.launchFrame(); }}
Java™ Module 10, slide 35 of 37Copyrig
rs
aris OS
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Combining Layout Manage
Sol
After user orprogram resizes
Java™ Module 10, slide 36 of 37Copyrig
ugh AWT just for this
sorPaneland
the componentow overlapped.
ct.drawing
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Drawing in AWT
• You can draw in any Component (althoprovides the Canvas and Panel classespurpose).
• Typically, you create a subclass ofCanvaoverride the paint method.
• The paintmethod is called every timeis shown (for example, if another windthe component and was then removed)
• Every component has a Graphics obje• The Graphics class implements many
methods.
Java™ Module 10, slide 37 of 37Copyrig
raphics
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Various Shapes Drawn by the GObject
Sun
Java™ Programmi
Services
ng Language
Module 11
GUI Event Handling
Java™ Module 11, slide 2 of 22Copyrig
in a GUI, including how
ed the event
ce for a variety
ethods for a
anonymous
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Objectives
• Define events and event handling• Write code to handle events that occur • Describe the concept of adapter classes
and when to use them• Determine the user action that originat
from the event object details• Identify the appropriate listener interfa
of event types• Create the appropriate event handler m
variety of event types• Understand the use of inner classes and
classes in event handling
Java™ Module 11, slide 3 of 22Copyrig
ke it useful?mouse click or
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Relevance
• What parts of a GUI are required to ma• How does a graphical program handle a
any other type of user interaction?
Java™ Module 11, slide 4 of 22Copyrig
penedents an event
ser’s interaction
vent e) {
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
What Is an Event?
• Events – Objects that describe what hap• Event sources – The generator of an ev• Event handlers – A method that receive
object, deciphers it, and processes the uFrame
Panel
Button
The user clicks on the button
Some Event HandleractionPerformed(ActionE ...}
ActionEvent
Java™ Module 11, slide 5 of 22Copyrig
ndlers.
ts when theyat component.
vent e) {
vent e) {
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Delegation Model
• An event can be sent to many event ha
• Event handlers register with componenare interested in events generated by th
Frame
Panel
Button
The user clicks on the button
Another Event Handler
One Event Handler
actionPerformed(ActionE ...}
actionPerformed(ActionE ...}ActionEvent
Java™ Module 11, slide 6 of 22Copyrig
GUI
lers for the type
n one type of
ork among
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Delegation Model
• Client objects (handlers) register with acomponent that they want to observe.
• GUI components only trigger the handof event that has occurred.
• Most components can trigger more thaevent.
• The delegation model distributes the wmultiple classes.
Java™ Module 11, slide 7 of 22Copyrig
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
A Listener Example
import java.awt.*;
public class TestButton { private Frame f; private Button b;
public TestButton() { f = new Frame("Test"); b = new Button("Press Me!"); b.setActionCommand("ButtonPressed"); }
public void launchFrame() {b.addActionListener(new ButtonHandler());
f.add(b,BorderLayout.CENTER); f.pack(); f.setVisible(true); }
Java™ Module 11, slide 8 of 22Copyrig
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Co
123 tener {456789
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A Listener Example
public static void main(String args[]) { TestButton guiApp = new TestButton(); guiApp.launchFrame(); }}
de for the event listener looks like this:
import java.awt.event.*;
public class ButtonHandler implements ActionLis public void actionPerformed(ActionEvent e) { System.out.println("Action occurred"); System.out.println("Button’s command is: " + e.getActionCommand()); }}
Java™ Module 11, slide 9 of 22Copyrig
java.util.EventObject
KeyEvent
MouseEvent
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Event Categoriesjava.awt.AWTEvent ActionEvent
AdjustmentEvent
ComponentEvent
TextEvent
ContainerEvent
FocusEvent
InputEvent
WindowEvent
java.awt.event
ItemEvent
Java™ Module 11, slide 10 of 22Copyrig
faces
Ca
Ac ActionEvent)
Item (ItemEvent)
Mo seEvent)useEvent)seEvent)eEvent)seEvent)
Momo
seEvent)Event)
Ke ent)vent)t)
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Method Categories and Inter
tegory Interface Name Methods
tion ActionListener actionPerformed(
ItemListener itemStateChanged
use MouseListener mousePressed(MoumouseReleased(MomouseEntered(MoumouseExited(MousmouseClicked(Mou
usetion
MouseMotionListener mouseDragged(MoumouseMoved(Mouse
y KeyListener keyPressed(KeyEvkeyReleased(KeyEkeyTyped(KeyEven
Java™ Module 11, slide 11 of 22Copyrig
ces
Ca
Foc sEvent)vent)
Ad hanged)
Co omponentEvent)ComponentEvent)(ComponentEvent)omponentEvent)
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Method Categories and Interfa
tegory Interface Name Methods
us FocusListener focusGained(FocufocusLost(FocusE
justment AdjustmentListener adjustmentValueC(AdjustmentEvent
mponent ComponentListener componentMoved(CcomponentHidden(componentResizedcomponentShown(C
Java™ Module 11, slide 12 of 22Copyrig
ces
Ca
Wi ndowEvent)dowEvent)WindowEvent)d(WindowEvent)dowEvent)WindowEvent)d(WindowEvent)
Co ontainerEvent)(ContainerEvent)
Tex (TextEvent)
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Method Categories and Interfa
tegory Interface Name Methods
ndow WindowListener windowClosing(WiwindowOpened(WinwindowIconified(windowDeiconifiewindowClosed(WinwindowActivated(windowDeactivate
ntainer ContainerListener componentAdded(CcomponentRemoved
t TextListener textValueChanged
Java™ Module 11, slide 13 of 22Copyrig
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Complex Example
import java.awt.*;import java.awt.event.*;
public class TwoListenerimplements MouseMotionListener, MouseLis
private Frame f; private TextField tf;
public TwoListener() { f = new Frame("Two listeners example"); tf = new TextField(30); }
Java™ Module 11, slide 14 of 22Copyrig
131415 se");16171819202122232425
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Complex Example
public void launchFrame() { Label label = new Label("Click and drag the mou // Add components to the frame f.add(label, BorderLayout.NORTH); f.add(tf, BorderLayout.SOUTH); // Add this object as a listener f.addMouseMotionListener(this); f.addMouseListener(this); // Size the frame and make it visible f.setSize(300, 200); f.setVisible(true); }
Java™ Module 11, slide 15 of 22Copyrig
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Complex Example
// These are MouseMotionListener events public void mouseDragged(MouseEvent e) { String s = "Mouse dragging: X = " + e.getX() + " Y = " + e.getY(); tf.setText(s); }
public void mouseEntered(MouseEvent e) { String s = "The mouse entered"; tf.setText(s); }
public void mouseExited(MouseEvent e) { String s = "The mouse has left the building"; tf.setText(s); }
Java™ Module 11, slide 16 of 22Copyrig
434445 he46474849505152535455565758
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Complex Example
// Unused MouseMotionListener method. // All methods of a listener must be present in t // class even if they are not used. public void mouseMoved(MouseEvent e) { }
// Unused MouseListener methods. public void mousePressed(MouseEvent e) { } public void mouseClicked(MouseEvent e) { } public void mouseReleased(MouseEvent e) { }
public static void main(String args[]) { TwoListener two = new TwoListener(); two.launchFrame(); }}
Java™ Module 11, slide 17 of 22Copyrig
of a program to
re called when
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Multiple Listeners
• Multiple listeners cause unrelated partsreact to the same event.
• The handlers of all registered listeners athe event occurs.
Java™ Module 11, slide 18 of 22Copyrig
extend adapterthat you need.
1234 {5678910111213
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Event Adapters
• The listener classes that you define canclasses and override only the methods
• An example is:import java.awt.*;import java.awt.event.*;
public class MouseClickHandler extends MouseAdapter
// We just need the mouseClick handler, so we use // an adapter to avoid having to write all the // event handler methods
public void mouseClicked(MouseEvent e) { // Do stuff with the mouse click... }}
Java™ Module 11, slide 19 of 22Copyrig
lasses
123456789101112 apter {1314 )15161718
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Event Handling Using Inner C
import java.awt.*;import java.awt.event.*;public class TestInner { private Frame f; private TextField tf; // used by inner class
public TestInner() { f = new Frame("Inner classes example"); tf = new TextField(30); }
class MyMouseMotionListener extends MouseMotionAd public void mouseDragged(MouseEvent e) { String s = "Mouse dragging: X = "+ e.getX( + " Y = " + e.getY();
tf.setText(s); } }
Java™ Module 11, slide 20 of 22Copyrig
sses
192021 se");2223242526 ner());2728293031323334353637
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Event Handling Using Inner Cla
public void launchFrame() { Label label = new Label("Click and drag the mou // Add components to the frame f.add(label, BorderLayout.NORTH); f.add(tf, BorderLayout.SOUTH); // Add a listener that uses an Inner class f.addMouseMotionListener(new MyMouseMotionListe f.addMouseListener(new MouseClickHandler()); // Size the frame and make it visible f.setSize(300, 200); f.setVisible(true); }
public static void main(String args[]) { TestInner obj = new TestInner(); obj.launchFrame(); }}
Java™ Module 11, slide 21 of 22Copyrig
E s Classes
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
vent Handling Using Anonymou
import java.awt.*;import java.awt.event.*;
public class TestAnonymous { private Frame f; private TextField tf;
public TestAnonymous() { f = new Frame("Anonymous classes example"); tf = new TextField(30); }
public static void main(String args[]) { TestAnonymous obj = new TestAnonymous(); obj.launchFrame(); }
Java™ Module 11, slide 22 of 22Copyrig
E Classes
1819 se");2021222324 () {2526 )2728293031 Not shown3233343536
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
vent Handling Using Anonymous
public void launchFrame() { Label label = new Label("Click and drag the mou // Add components to the frame f.add(label, BorderLayout.NORTH); f.add(tf, BorderLayout.SOUTH); // Add a listener that uses an anonymous class f.addMouseMotionListener(new MouseMotionAdapter public void mouseDragged(MouseEvent e) { String s = "Mouse dragging: X = "+ e.getX( + " Y = " + e.getY(); tf.setText(s); } }); // <- note the closing parenthesis f.addMouseListener(new MouseClickHandler()); // // Size the frame and make it visible f.setSize(300, 200); f.setVisible(true); }}
Sun
Java™ Programmi
ns
Services
ng Language
Module 12
GUI-Based Applicatio
Java™ Module 12, slide 2 of 18Copyrig
the events that
menu, and
d font of a
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Objectives
• Identify the key AWT components andthey trigger
• Describe how to construct a menu bar, menu items in a Java GUI
• Understand how to change the color ancomponent
Java™ Module 12, slide 3 of 18Copyrig
I for bothut. However,
ich GUIs can becomponents
UI frame?
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Relevance
• You now know how to set up a Java GUgraphic output and interactive user inponly a few of the components from whbuilt have been described. What other would be useful in a GUI?
• How can you create a menu for your G
Java™ Module 12, slide 4 of 18Copyrig
Co
But for receiving mouse
Can
Che to select an item
Che
Cho
Com nts, except menu
Con s
Dia and a border;al
Fra ws with window
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
AWT Components
mponent Type Description
ton A named rectangular box used clicks
vas A panel used for drawing
ckbox A component enabling the user
ckboxMenuItem A checkbox within a menu
ice A pull-down static list of items
ponent The parent of all AWT componecomponents
tainer The parent of all AWT container
log A top-level window with a titledialogs can be modeless or mod
me The base class of all GUI windomanager controls
Java™ Module 12, slide 5 of 18Copyrig
Co
Lab
Lis namic set of items
Men , which contains a
Men
Pan st often to create
Scr r to select from a
Scr ts automatic for a single child
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
AWT Components
mponent Type Description
el A text string component
t A component that contains a dy
u An element under the menu barset of menu items
uItem An item within a menu
el A basic container class used mocomplex layouts
ollbar A component that enables a userange of values
ollPane A container class that implemenhorizontal and vertical scrollingcomponent
Java™ Module 12, slide 6 of 18Copyrig
Co
Tex ser to enter a block
Tex ser to enter a single
Win s, without window
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
AWT Components
mponent Type Description
tArea A component that enables the uof text
tField A component that enables the uline of text
dow The base class of all GUI windowmanager controls
Java™ Module 12, slide 7 of 18Copyrig
CoTy
u MM Text Win
But ✓
Can ✓
Che ✓
CheMen
Cho ✓
Com ✓
Con ✓
Dia ✓
Fra ✓
Lab ✓
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
AWT Listeners
mponentpe
Act Adj Cmp Cnt Foc Itm Key Mo
ton ✓ ✓ ✓ ✓ ✓
vas ✓ ✓ ✓ ✓
ckbox ✓ ✓ ✓ ✓ ✓
ckbox-uItem
✓
ice ✓ ✓ ✓ ✓ ✓
ponent ✓ ✓ ✓ ✓
tainer ✓ ✓ ✓ ✓ ✓
log ✓ ✓ ✓ ✓ ✓
me ✓ ✓ ✓ ✓ ✓
el ✓ ✓ ✓ ✓
Java™ Module 12, slide 8 of 18Copyrig
CoTy
u MM Text Win
Lis ✓
Men
Pan ✓
Scr ✓
Scr ✓
Tex ✓ ✓
Tex ✓ ✓
Win ✓ ✓ ✓
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
AWT Listeners
mponentpe
Act Adj Cmp Cnt Foc Itm Key Mo
t ✓ ✓ ✓ ✓ ✓ ✓
uItem ✓
el ✓ ✓ ✓ ✓ ✓
ollbar ✓ ✓ ✓ ✓ ✓
ollPane ✓ ✓ ✓ ✓ ✓
tArea ✓ ✓ ✓ ✓
tField ✓ ✓ ✓ ✓ ✓
dow ✓ ✓ ✓ ✓ ✓
Java™ Module 12, slide 9 of 18Copyrig
a menu
dd them to the
and add them
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
How to Create a Menu
1. Create a MenuBar object, and set it intocontainer, such as a Frame.
2. Create one or more Menu objects, and amenu bar object.
3. Create one or more MenuItem objects,to the menu object.
Java™ Module 12, slide 10 of 18Copyrig
123
ndows
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Creating a MenuBar
Frame f = new Frame("MenuBar");MenuBar mb = new MenuBar();f.setMenuBar(mb);
Solaris OS Microsoft Wi
Java™ Module 12, slide 11 of 18Copyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Creating a Menu
Frame f = new Frame("Menu");MenuBar mb = new MenuBar();Menu m1 = new Menu("File");Menu m2 = new Menu("Edit");Menu m3 = new Menu("Help");mb.add(m1);mb.add(m2);mb.setHelpMenu(m3);f.setMenuBar(mb);
Java™ Module 12, slide 12 of 18Copyrig
ndows
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Creating a Menu
Solaris OSMicrosoft Wi
Java™ Module 12, slide 13 of 18Copyrig
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Creating a MenuItem
MenuItem mi1 = new MenuItem("New");MenuItem mi2 = new MenuItem("Save");MenuItem mi3 = new MenuItem("Load");MenuItem mi4 = new MenuItem("Quit");mi1.addActionListener(this);mi2.addActionListener(this);mi3.addActionListener(this);mi4.addActionListener(this);m1.add(mi1);m1.add(mi2);m1.add(mi3);m1.addSeparator();m1.add(mi4);
Java™ Module 12, slide 14 of 18Copyrig
ndows
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Creating a MenuItem
Solaris OSMicrosoft Wi
Java™ Module 12, slide 15 of 18Copyrig
tem
1234567891011121314 tent");1516
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Creating a CheckBoxMenuI
MenuBar mb = new MenuBar();Menu m1 = new Menu("File");Menu m2 = new Menu("Edit");Menu m3 = new Menu("Help");mb.add(m1);mb.add(m2);mb.setHelpMenu(m3);f.setMenuBar(mb);.....MenuItem mi2 = new MenuItem("Save");mi2.addActionListener(this);m1.add(mi2);......CheckboxMenuItem mi5 = new CheckboxMenuItem("Persismi5.addItemListener(this);m1.add(mi5);
Java™ Module 12, slide 16 of 18Copyrig
tem
ndows
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Creating a CheckBoxMenuI
Solaris OSMicrosoft Wi
Java™ Module 12, slide 17 of 18Copyrig
ts
Co I include:
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Controlling Visual Aspec
mmands to control visual aspects of the GU
• Colors:setForeground()setBackground()
• Example:Color purple = new Color(255, 0, 255);Button b = new Button(“Purple”);b.setBackground(purple);
Java™ Module 12, slide 18 of 18Copyrig
y
wing) toolkit.he components
much moree, JTree, and
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
J.F.C./Swing Technolog
• Java Foundation Class/Swing (J.F.C./Stechnology is a second-generation GUI
• It builds on top of AWT, but supplants twith lightweight versions.
• There are many more components, andcomplex components, including JTablJComboBox.
Sun
Java™ Programmi
Services
ng Language
Module 13
Threads
Java™ Module 13, slide 2 of 37Copyrig
ology program,sed by that
rite platform-
when multiple
etween threads corruption
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Objectives
• Define a thread• Create separate threads in a Java techn
controlling the code and data that are uthread
• Control the execution of a thread and windependent code with threads
• Describe the difficulties that might arisethreads share data
• Use waitand notify to communicate b• Use synchronized to protect data from
Java™ Module 13, slide 3 of 37Copyrig
Ho le taskscon
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Relevance
w do you get programs to perform multipcurrently?
Java™ Module 13, slide 4 of 37Copyrig
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Threads
• What are threads?Threads are a virtual CPU.
• The three parts of at thread are:• CPU• Code• Data
CPU
Code Data
A thread orexecution context
Java™ Module 13, slide 5 of 37Copyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Creating the Thread
public class ThreadTester { public static void main(String args[]) { HelloRunner r = new HelloRunner(); Thread t = new Thread(r); t.start(); }}class HelloRunner implements Runnable { int i; public void run() { i = 0; while (true) { System.out.println("Hello " + i++); if ( i == 50 ) { break; } } }}
Java™ Module 13, slide 6 of 37Copyrig
characteristics:ble instance.e.
”nner
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Creating the Thread
• Multithreaded programming has these• Multiple threads are from one Runna• Threads share the same data and cod
• For example:Thread t1 = new Thread(r);Thread t2 = new Thread(r);
CPU
Code DataHelloRunner Instance “r
Thread t}New Thread
Class of HelloRu
Java™ Module 13, slide 7 of 37Copyrig
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Starting the Thread
• Use the start method.• Place the thread in a runnable state.
Java™ Module 13, slide 8 of 37Copyrig
N Dead
run() Completes
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Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Thread Scheduling
Runnable
ew
RunningScheduler
Blocked
Unblocked Event Blocked
start()
Java™ Module 13, slide 9 of 37Copyrig
ple
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Thread Scheduling Exam
public class Runner implements Runnable { public void run() { while (true) { // do lots of interesting stuff
// ...// Give other threads a chance
try {Thread.sleep(10);
} catch (InterruptedException e) { // This thread’s sleep was interrupted // by another thread } } }}
Java™ Module 13, slide 10 of 37Copyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Terminating a Thread
public class Runner implements Runnable { private boolean timeToQuit=false;
public void run() { while ( ! timeToQuit ) { // continue doing work } // clean up before run() ends }
public void stopRunning() { timeToQuit=true; }}
Java™ Module 13, slide 11 of 37Copyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Terminating a Thread
public class ThreadController { private Runner r = new Runner(); private Thread t = new Thread(r);
public void startThread() { t.start(); }
public void stopThread() { // use specific instance of Runner r.stopRunning(); }}
Java™ Module 13, slide 12 of 37Copyrig
s
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Basic Control of Thread
• Test threads:isAlive()
• Access thread priority:getPriority()setPriority()
• Put threads on hold:Thread.sleep() // static methodjoin()Thread.yield() // static method
Java™ Module 13, slide 13 of 37Copyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The joinMethod
public static void main(String[] args) { Thread t = new Thread(new Runner()); t.start(); ... // Do stuff in parallel with the other thread for ... // Wait here for the other thread to finish try { t.join(); } catch (InterruptedException e) { // the other thread came back early } ... // Now continue in this thread ...}
Java™ Module 13, slide 14 of 37Copyrig
ads
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Other Ways to Create Thre
public class MyThread extends Thread { public void run() { while ( true ) { // do lots of interesting stuff try { Thread.sleep(100); } catch (InterruptedException e) { // sleep interrupted } } }
public static void main(String args[]) { Thread t = new MyThread(); t.start(); }}
Java™ Module 13, slide 15 of 37Copyrig
reads
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Selecting a Way to Create Th
• Implement Runnable:• Better object-oriented design• Single inheritance• Consistency
• Extend Thread:Simpler code
Java™ Module 13, slide 16 of 37Copyrig
yword
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Using the synchronizedKe
public class MyStack {
int idx = 0; char [] data = new char[6];
public void push(char c) { data[idx] = c; idx++; }
public char pop() { idx--; return data[idx]; }}
Java™ Module 13, slide 17 of 37Copyrig
lock flag. with the lock
h(char c) {(this) { c;
onized(this)
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Object Lock Flag
• Every object has a flag that is a type of• The synchronized enables interaction
flag.
Object this
public void pussynchronized data[idx] =idx++;
}}
Thread before synchr
Code orBehavior
Data orState
Java™ Module 13, slide 18 of 37Copyrig
h(char c) {(this) { c;
nized(this)
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Object Lock Flag
Object this
public void pussynchronized data[idx] =idx++;
}}
Thread after synchro
Code orBehavior
Data orState
Java™ Module 13, slide 19 of 37Copyrig
op() {d (this) {
ta[idx];
ing tozed(this)
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The Object Lock Flag
Object this
public char psynchronizeidx--;return da
}}
Another thread, try
Waiting for
lock flag missing
object lock
Code orBehavior
Data orState
execute synchroni
Java™ Module 13, slide 20 of 37Copyrig
Th ts:
d of the
eturn, ored code block
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Releasing the Lock Flag
e lock flag is released in the following even
• Released when the thread passes the ensynchronized code block
• Released automatically when a break, rexception is thrown by the synchroniz
Java™ Module 13, slide 21 of 37Copyrig
t Together
nchronized.ed should be
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Using synchronized– Putting I
• All access to delicate data should be sy• Delicate data protected by synchroniz
private.
Java™ Module 13, slide 22 of 37Copyrig
t Together
Th ent:
publ sy }}
publ//
}
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Using synchronized– Putting I
e following two code segments are equival
ic void push(char c) {nchronized(this) {// The push method code
ic synchronized void push(char c) { The push method code
Java™ Module 13, slide 23 of 37Copyrig
T ronization
N Dead
run() Completes
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
hread State Diagram With Synch
Blocked inObject’s
Lock Pool
Runnable
ew
RunningScheduler
Blocked
Unblocked Event Blocked
Lock Acquired Synchronized
start()
Java™ Module 13, slide 24 of 37Copyrig
A d
from the other.
s
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Deadlock
eadlock has the following characteristics:
• It is two threads, each waiting for a lock• It is not detected or avoided.• Deadlock can be avoided by:
• Deciding on the order to obtain lock• Adhering to this order throughout• Releasing locks in reverse order
Java™ Module 13, slide 25 of 37Copyrig
notify
two threads.
at your
stination and
pon arrival at
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Thread Interaction – waitand
• Scenario:Consider yourself and a cab driver as
• The problem:How do you determine when you aredestination?
• The solution:• You notify the cab driver of your de
relax.• The driver drives and notifies you u
your destination.
Java™ Module 13, slide 26 of 37Copyrig
Th
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Thread Interaction
read interactions include:
• The wait and notify methods• The pools:
• Wait pool• Lock pool
Java™ Module 13, slide 27 of 37Copyrig
Th nd notify
Blocked inObject’s
Wait Pool
New Dead
un() Completes
)
wait()[Must have lock]/Releases lock
st
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
read State Diagram With wait a
notify() orBlocked inObject’s
Lock Pool
Runnable RunningScheduler
Blocked
Unblocked Event Blocked
r
Lock Acquired Synchronized
interrupt(
art()
Java™ Module 13, slide 28 of 37Copyrig
zation
notifications in
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Monitor Model for Synchroni
• Leave shared data in a consistent state.• Ensure programs cannot deadlock.• Do not put threads expecting different
the same wait pool.
Java™ Module 13, slide 29 of 37Copyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The ProducerClass
package mod13;
public class Producer implements Runnable { private SyncStack theStack; private int num; private static int counter = 1;
public Producer (SyncStack s) { theStack = s; num = counter++; }
Java™ Module 13, slide 30 of 37Copyrig
13141516171819 c);202122232425262728
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The ProducerClass
public void run() { char c;
for (int i = 0; i < 200; i++) { c = (char)(Math.random() * 26 +’A’); theStack.push(c); System.out.println(“Producer” + num + “: “ + try { Thread.sleep((int)(Math.random() * 300)); } catch (InterruptedException e) { // ignore it } } } // END run method
} // END Producer class
Java™ Module 13, slide 31 of 37Copyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The ConsumerClass
package mod13;
public class Consumer implements Runnable { private SyncStack theStack; private int num; private static int counter = 1;
public Consumer (SyncStack s) { theStack = s; num = counter++; }
Java™ Module 13, slide 32 of 37Copyrig
1314151617 c);181920212223242526
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The ConsumerClass
public void run() { char c; for (int i = 0; i < 200; i++) { c = theStack.pop(); System.out.println(“Consumer” + num + “: “ +
try { Thread.sleep((int)(Math.random() * 300)); } catch (InterruptedException e) { // ignore it } } } // END run method
Java™ Module 13, slide 33 of 37Copyrig
Th
publ
pr ter>(400);
pu
}
pu
}}
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The SyncStackClass
is is a sketch of the SyncStack class:
ic class SyncStack {
ivate List<Character> buffer = new ArrayList<Charac
blic synchronized char pop() {// pop code here
blic synchronized void push(char c) {// push code here
Java™ Module 13, slide 34 of 37Copyrig
91011121314151617181920
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The popMethod
public synchronized char pop() { char c; while (buffer.size() == 0) { try { this.wait(); } catch (InterruptedException e) { // ignore it... } } c = buffer.remove(buffer.size()-1); return c; }
Java™ Module 13, slide 35 of 37Copyrig
22232425
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The pushMethod
public synchronized void push(char c) { this.notify(); buffer.add(c); }
Java™ Module 13, slide 36 of 37Copyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The SyncTestClass
package mod13;public class SyncTest { public static void main(String[] args) { SyncStack stack = new SyncStack(); Producer p1 = new Producer(stack); Thread prodT1 = new Thread (p1); prodT1.start(); Producer p2 = new Producer(stack); Thread prodT2 = new Thread (p2); prodT2.start();
Consumer c1 = new Consumer(stack); Thread consT1 = new Thread (c1); consT1.start(); Consumer c2 = new Consumer(stack); Thread consT2 = new Thread (c2); consT2.start(); }}
Java™ Module 13, slide 37 of 37Copyrig
ProdConsProdConsProdProdProdConsConsProdProdConsConsProdConsProdConsCons
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The SyncTestClass
ucer2: Fumer1: Fucer2: Kumer2: Kucer2: Tucer1: Nucer1: Vumer2: Vumer1: Nucer2: Vucer2: Uumer2: Uumer2: Vucer1: Fumer1: Fucer2: Mumer2: Mumer2: T
Sun
Java™ Programmi
s
Services
ng Language
Module 14
Advanced I/O Stream
Java™ Module 14, slide 2 of 22Copyrig
io package, and use them
treams, and
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Objectives
• Describe the main features of the java.• Construct node and processing streams
appropriately• Distinguish readers and writers from s
select appropriately between them
Java™ Module 14, slide 3 of 22Copyrig
he Javate from sources
pported in I/O
s of character
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Relevance
• What mechanisms are in place within tprogramming language to read and wri(or sinks) other than files?
• How are international character sets suoperations?
• What are the possible sources and sinkand byte streams?
Java™ Module 14, slide 4 of 22Copyrig
data from a
a, also called an
a, also called an
.y, and pipes
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
I/O Fundamentals
• A stream can be thought of as a flow of source or to a sink.
• A source stream initiates the flow of datinput stream.
• A sink stream terminates the flow of datoutput stream.
• Sources and sinks are both node streams• Types of node streams are files, memor
between threads or processes.
Java™ Module 14, slide 5 of 22Copyrig
ses
Str racter Streams
Sou der
Sin ter
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Fundamental Stream Clas
eam Byte Streams Cha
rce streams InputStream Rea
k streams OutputStream Wri
Java™ Module 14, slide 6 of 22Copyrig
streams:
andled by
d by input
byte stream.haracter
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Data Within Streams
• Java technology supports two types of character and byte.
• Input and output of character data is hreaders and writers.
• Input and output of byte data is handlestreams and output streams:• Normally, the term stream refers to a• The terms reader and writer refer to c
streams.
Java™ Module 14, slide 7 of 22Copyrig
ds
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The InputStreamMetho
• The three basic read methods are:int read()int read(byte[] buffer)int read(byte[] buffer, int offset, int length)
• Other methods include:void close()int available()long skip(long n)boolean markSupported()void mark(int readlimit)void reset()
Java™ Module 14, slide 8 of 22Copyrig
ds
h)
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The OutputStreamMetho
• The three basic write methods are:void write(int c)void write(byte[] buffer)void write(byte[] buffer, int offset, int lengt
• Other methods include:void close()void flush()
Java™ Module 14, slide 9 of 22Copyrig
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The ReaderMethods
• The three basic read methods are:int read()int read(char[] cbuf)int read(char[] cbuf, int offset, int length)
• Other methods include:void close()boolean ready()long skip(long n)boolean markSupported()void mark(int readAheadLimit)void reset()
Java™ Module 14, slide 10 of 22Copyrig
h)
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The WriterMethods
• The basic write methods are:void write(int c)void write(char[] cbuf)void write(char[] cbuf, int offset, int length)void write(String string)void write(String string, int offset, int lengt
• Other methods include:void close()void flush()
Java™ Module 14, slide 11 of 22Copyrig
Ty ms
Fil StreamtStream
Mearr
InputStreamOutputStream
Mestr
Pip tStreamutStream
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Node Streams
pe Character Streams Byte Strea
e FileReaderFileWriter
FileInputFileOutpu
mory:ay
CharArrayReaderCharArrayWriter
ByteArrayByteArray
mory:ing
StringReaderStringWriter
N/A
e PipedReaderPipedWriter
PipedInpuPipedOutp
Java™ Module 14, slide 12 of 22Copyrig
Th sing a manualbu
jav
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
A Simple Example
is program performs a copy file operation uffer:
a TestNodeStreams file1 file2
import java.io.*;
public class TestNodeStreams { public static void main(String[] args) { try { FileReader input = new FileReader(args[0]); FileWriter output = new FileWriter(args[1]); char[] buffer = new char[128]; int charsRead;
// read the first buffer charsRead = input.read(buffer);
Java™ Module 14, slide 13 of 22Copyrig
13141516171819202122232425262728
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
A Simple Example
while ( charsRead != -1 ) {// write the buffer out to the output fileoutput.write(buffer, 0, charsRead);
// read the next buffercharsRead = input.read(buffer);
}
input.close(); output.close(); } catch (IOException e) { e.printStackTrace(); } }}
Java™ Module 14, slide 14 of 22Copyrig
Th sing a built-inbu
jav
123456 s[0]);7 (input);8 s[1]);9 (output);10111213
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Buffered Streams
is program performs a copy file operation uffer:
a TestBufferedStreams file1 file2
import java.io.*;
public class TestBufferedStreams { public static void main(String[] args) { try { FileReader input = new FileReader(arg BufferedReader bufInput = new BufferedReader FileWriter output = new FileWriter(arg BufferedWriter bufOutput = new BufferedWriter String line;
// read the first line line = bufInput.readLine();
Java™ Module 14, slide 15 of 22Copyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Buffered Streams
while ( line != null ) {// write the line out to the output filebufOutput.write(line, 0, line.length());bufOutput.newLine();// read the next lineline = bufInput.readLine();
}bufInput.close();
bufOutput.close();} catch (IOException e) {
e.printStackTrace(); } }}
Java™ Module 14, slide 16 of 22Copyrig
Program
Data Sink
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
I/O Stream Chaining
Data Source
FileInputStreamBufferedInputStream
DataInputStream
Program
FileOutputStreamBufferedOutputStream
DataOutputStream
Input Stream Chain
Output Stream Chain
Java™ Module 14, slide 17 of 22Copyrig
Ty ams
Bu InputStreamOutputStream
Filt nputStreamutputStream
Cobetand
Perobjser
putStreamtputStream
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Processing Streams
pe Character Streams Byte Stre
ffering BufferedReaderBufferedWriter
BufferedBuffered
ering FilterReaderFilterWriter
FilterIFilterO
nvertingween bytes character
InputStreamReaderOutputStreamWriter
formingectialization
ObjectInObjectOu
Java™ Module 14, slide 18 of 22Copyrig
Ty ams
Percon
tStreamutStream
Co erInputStream
Pee InputStream
Pri eam
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Processing Streams
pe Character Streams Byte Stre
forming dataversion
DataInpuDataOutp
unting LineNumberReader LineNumb
king ahead PushbackReader Pushback
nting PrintWriter PrintStr
Java™ Module 14, slide 19 of 22Copyrig
rarchy
nputStream
ackInputStream
redInputStream
umberInputStream
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The InputStreamClass Hie
InputStream
FileInputStream
ObjectInputStream
PipedInputStream
StringBufferInputStream
FilterInputStream
ByteArrayInputStream
DataI
Pushb
Buffe
LineN
SequenceInputStream
Java™ Module 14, slide 20 of 22Copyrig
rarchy
aOutputStream
ntStreamntStream
feredOutputStream
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The OutputStreamClass Hie
OutputStream
FileOutputStream
ObjectOutputStream
FilterOutputStream
ByteArrayOutputStream
Dat
PriPri
Buf
PipedOutputStream
Java™ Module 14, slide 21 of 22Copyrig
hy
eader
erReader
ader
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The ReaderClass Hierarc
Reader
BufferedReader
CharArrayReader
PipedReader
FilterReader
StringReader
FileRInputStreamReader
LineNumb
PushbackRe
Java™ Module 14, slide 22 of 22Copyrig
hy
eWriter
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
The WriterClass Hierarc
Writer
BufferedWriter
CharArrayWriter
PrintWriter
PipedWriter
FilterWriter
StringWriter
FilOutputStreamWriter
Sun
Java™ Programmi
Services
ng Language
Module 15
Networking
Java™ Module 15, slide 2 of 12Copyrig
nection
forservers
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Objectives
• Develop code to set up the network con• Understand the TCP/IP Protocol• Use ServerSocket and Socket classes
implementation of TCP/IP clients and
Java™ Module 15, slide 3 of 12Copyrig
Ho nt machine anda s
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Relevance
w can a communication link between a clieerver on the network be established?
Java™ Module 15, slide 4 of 12Copyrig
Th
So
am and an
ams.
Se
Set telephonesys ch must belist
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Networking
is section describes networking concepts.
ckets
• Sockets hold two streams: an input streoutput stream.
• Each end of the socket has a pair of stre
tting Up the Connection
up of a network connection is similar to a tem: One end must dial the other end, whiening.
Java™ Module 15, slide 5 of 12Copyrig
o.com
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Networking
client.bar.com
client.baz.com
server.fo
18000
18002
3000
Java™ Module 15, slide 6 of 12Copyrig
ology
following:hinese at the server
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Networking With Java Techn
• To address the connection, include the • The address or name of remote mac• A port number to identify the purpo
• Port numbers range from 0–65535.
Java™ Module 15, slide 7 of 12Copyrig
l
t#)
)
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Java Networking Mode
Server
ServerSocket (port #)
OutputStream
InputStream
Socket.close()
Client
Socket (host, por
OutputStream
InputStream
Socket.close(
Register withthis service
Wait for aconnection
(Attempt to connect)Socket()
ServerSocket.accept()
Java™ Module 15, slide 8 of 12Copyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Minimal TCP/IP Server
import java.net.*;import java.io.*;
public class SimpleServer { public static void main(String args[]) { ServerSocket s = null;
// Register your service on port 5432 try {
s = new ServerSocket(5432); } catch (IOException e) { e.printStackTrace(); }
Java™ Module 15, slide 9 of 12Copyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Minimal TCP/IP Server
// Run the listen/accept loop forever while (true) { try { // Wait here and listen for a connection
Socket s1 = s.accept();
// Get output stream associated with the so OutputStream s1out = s1.getOutputStream( BufferedWriter bw = new BufferedWriter( new OutputStreamWriter(s1out));
// Send your string! bw.write(“Hello Net World!\n”);
Java™ Module 15, slide 10 of 12Copyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Minimal TCP/IP Server
// Close the connection, but not the serverbw.close();s1.close();
} catch (IOException e) { e.printStackTrace(); } // END of try-catch
} // END of while(true)
} // END of main method
} // END of SimpleServer program
Java™ Module 15, slide 11 of 12Copyrig
123456789 54321011 ;1213141516 ;
Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Minimal TCP/IP Client
import java.net.*;import java.io.*;
public class SimpleClient {
public static void main(String args[]) {
try { // Open your connection to a server, at port // localhost used here
Socket s1 = new Socket("127.0.0.1", 5432)
// Get an input stream from the socket InputStream is = s1.getInputStream(); // Decorate it with a "data" input stream DataInputStream dis = new DataInputStream(is)
Java™ Module 15, slide 12 of 12Copyrig
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Sun Services
Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1
Minimal TCP/IP Client
// Read the input and print it to the screen System.out.println(dis.readUTF());
// When done, just close the steam and connec dis.close(); s1.close();
} catch (ConnectException connExc) { System.err.println("Could not connect.");
} catch (IOException e) { // ignore } // END of try-catch
} // END of main method
} // END of SimpleClient program