Java Programing Language

SESSION 01 – Introduction to Java

OBJECTIVES• History of Java• Java Virtual Machine• Features of Java• JRE and JDK• Choosing a development environment• Writing a simple Java program• Using the command-line tools• Using Java NetBeans and Eclipse

History of Java• Developed and maintained by Sun MicroSystems

(Oracle - 2010)– Since 1991– James Gosling– Originally called Oak

• Aimed at producing an operating environment for networked devices and embedded systems– “Write once, run anywhere”– Java is currently one of the most popular

programming language

The Java history timeline• 1991: Oak Language• 1995: Name changed from Oak to Java• 1996: JDK 1.0• 1997: JDK 1.1• 1998: J2EE, J2SE, J2ME• 2000: J2SE(EE) 1.3• 2002: J2SE(EE) 1.4• 2004: J2SE(EE) 5 (1.5)• 2006: Java SE(EE) 6• 2008: JavaFX 1.0• 2011: Java SE 7

1.01.1

J2SE

J2ME

J2EE

6.0

1.4

7.0

Java Virtual Machine• Java is both a compiled and an interpreted language

– Source code is compiled into Java bytecode– bytecode is then interpreted by the Java Virtual Machine

(JVM)

Java Virtual Machine (cont)Java Code

Byte Code (.class)

JVM

Windows LinuxMac

Java language for Mobile application development

• Android (Java)• Bada (C++)• Black Berry (Java)• iPhone, iPad (Objective-C)• Java Me (Java)• WebOs (C , C++, Javascript, HTML)• Symbian (C++)• Windows Mobile (VC++,C++)• Windows Phone (C#)

Features of Java• Simple• Object-Oriented• Platform-independent• Robust• Secure• Distributed• Multi-threaded

Features of Java (cont)• Simple:

– The syntax is mostly derived from C and C++– Java has simplified C++ programming by remove

some of complicated and difficult from C++• Goto statement• Overload operator• Pointer• Header• Union, struct• …

Features of Java (cont)• Object-Oriented:

– Except for primitive data types, everything in Java is an object

– There are no global functions in Java: all functions are invoked through an object

– Java’s support for Object-Orientation includes inheritance, polymorphism, data access levels…

– Not support multiple inheritance

Features of Java (cont)• Platform-independent:

– Java was conceived with the concept of WORA: “Write once, Run anywhere"

– Java code (.java) is compiled a byte code which is independent of the system

– Java byte code (.class) can run on any device equipped with a Java Virtual Machine

Features of Java (cont)• Robust: Java can be used to solve some very

complex programming problems with the supporting of:– Variety of data types– Distributed– Multithreaded– Garbage collection– …

Features of Java (cont)• Secure:

– No pointers are forged. – No illegal object casts are performed. – There will be no operand stack overflows or

underflows. – All parameters passed to functions are of the

proper types. – Rules regarding private, protected, and public

class membership are followed.

Features of Java (cont)• Distributed:

– Java facilitates the building of distributed applications by a collection of classes for use in networked applications.

– By using Java's URL class, an application can easily access a remote server. Classes also are provided for establishing socket-level connections.

• Multi-threaded:– Multiple, synchronized threads is built directly into the

Java language and runtime environment– Synchronized threads are useful in creating distributed,

network-aware applications

Java compared with other languages

• Java and C/C++• Java and C#• Java and script language such as PHP, Perl,

Python, Ruby• Java and JavaScript

The popularity of JavaProgramming

LanguagePosition

May 2011Position

May 2006Position

May 1996Position

May 1986Java 1 1 3 -

C 2 2 1 1C++ 3 3 2 5C# 4 7 - -

PHP 5 4 - -Objective-C 6 43 - -

Python 7 8 - -Visual Basic 8 5 4 6

Perl 9 6 6 -Ruby 10 18 - -Lisp 15 14 9 3Ada 16 16 8 2

JDK and JRE• The two principal products in the Java SE

platform: Java Development Kit (JDK) and Java Runtime Environment (JRE).– The JRE provides the libraries, Java virtual machine,

and other components necessary for running applets and applications written in the Java programming language

– The JDK includes the JRE plus development tools such as compilers and debuggers that are necessary or useful for developing applets and applications

JDK and JRE

Download and install JDK• The JDK is a development environment for building

applications, applets, and components using the Java programming language.

• JDK can be download at http://www.oracle.com• After downloading the JDK, follow the platform-

dependent installation directions. At the time of this writing, they were available at http://java.sun.com/javase/6/webnotes/install/index.html.

Navigating the Java Directories• The JDK has the directory structure shown

below:JDK 1.6.0_<version>

Readme.html

jre

bin lib

include

lib

bin

LICENSE

COPYRIGHT

README.txt

demo

Setting the Execution Path1. Click Start > Control Panel > System on

Windows XP or Start > Settings > Control Panel > System (on Windows XP.)

2. Click Advanced > Environment Variables.3. Add the location of bin folder of JDK

installation for PATH in User Variables and System Variables. A typical value for PATH is: C:\Program Files\Java\jdk1.6.0_<version>\bin

Write a simple Java programThe first application will simply display the greeting "Hello world!"

• Step 1: Create a source file public class Helloworld {

public static void main(String[] args){System.out.println("Hello world");

}}

• Step 2: Compile the source file into a .class file• Step 3: Run the program

Write a simple Java programWrite Java code using an editor

javac Helloworld.java

java Helloworld

Java code: Helloworld.java

Bytecode: Helloworld.class

Text Editor

Output

Save the file with a .java extension

Run the Java compiler 'javac'

Execute the bytecode with the command 'java'

This creates a file of bytecode with a .class extension

Using the Command-Line Tools• Open a shell indow. Go to directory where you

store your Helloworld.java and use javac

Using the Command-Line Tools• The javac has a set of standard options:

– classpath classpath– d directory– encoding encoding – g – help – nowarn – source release – sourcepath sourcepath – target version – …

Choosing a Development Environment

• NetBeans• Jbuilder• Eclipse

Using Java NetBeans

Using Eclipse

• Create a Java Project:

Using Eclipse

• Write a simple program:

Using Eclipse

Using Eclipse• Program’s output in Console window:

Comments• Java has three ways of marking comments:

– The most commonmethod is a //– Use the /* and */ comment to block off a longer

comment– Use a /** to start and a */ to end in order to

generate documentation automatically

Summary• In this session, we learnt:

– History of Java– Java Virtual Machine– Types of Java programs– Features of Java– JRE and JDK– Choosing a development environment– Writing a simple Java program– Using the command-line tools– Using Java NetBeans and Eclipse– Basic of Java