CSE 1340CSE 1340Class 3 Class 3

Class 03 objectivesClass 03 objectives State the difference between Machine Language vs. High

Level Languages Discuss some characteristics of the Java language Write an algorithm Differentiate between the compilation and execution

processes of a program Understand the purpose of using a compiler Gain an elementary understanding of object-oriented

programming

Evolution of computer languagesEvolution of computer languages Machine language

– Characterized by binary ones and zeroes Low-level assembly languages

– Characterized by mnemonic codes High-level languages

– English-like Very-high level languages

– Results instead of procedural oriented Natural languages

– Conversational

What Is Java?What Is Java?

High-level languageObject-oriented

– Data and operations are packaged into a single unit called an object

Basic syntax derived from C, C++, and Smalltalk– Designed by a team from Sun

Microsystems led by James Gosling in the early 1990’s

What Is Java?What Is Java?

Parsimonious– Compatible with older versions

Robust– Strongly typed and incorruptible data

Secure– Protection against misuse of code

Portable– Platform-independent

What Is the Java SDK?What Is the Java SDK?

The Java Software Development Kit (SDK) is a programming package to develop Java applications

The Java Runtime Environment (JRE) provides the tools to deploy Java applications

Features of the J2SEFeatures of the J2SE

The Java Compiler– Converts code into bytecode

The Java Virtual Machine – Contains an interpreter to execute the

bytecode

The Java API– The standard set of packages available in Java

The Java Applet Viewer– Mini browser to display Java applets

Any Java Compiler that is compatible with the

Java 2 Platform 6.0 (J2SE 6.0)

Please see your Blackboard homepage for link to free download of Sun Microsystems J2SE 6.0

If you use J2SE 6.0, it is a command line interface. In other words, there is no User Interface to work with. Programs have to be entered into a text editor, saved and then compiled through commands at a command prompt. Instructions for doing so are in a link on your Blackboard homepage.

Your textbook also comes with a CD that includes Textpad that make coding a little easier. See textbook for installation.

See also the link on your Blackboard homepage for instructions on using the NetBeans platform as another option.

Editor

Compiler

Class Loader

Byte Code Verifier

..

..

..

Interpreter

..

..

..

..

..

..

Editor DiskProgram1.java

Compiler DiskProgram1.javaProgram1.class

Class Loader

.

.

.

PrimaryPrimaryMemoryMemory

Program1.classDiskProgram1.classProgram1.html

Java Virtual MachineJava Virtual Machine

JVM

Java Source code .java

Java byte-code .class

Environment

Java VMjavac java

Byte CodeVerifier .

.

.

PrimaryPrimaryMemoryMemory

Program1.class

JIT CompilerJIT Compiler

JIT- takes byte-codes and change it to machine code.

JVMRunning

Applet or Application

J.I.T.Compiler

.class file

machine code

Interpreter ...

PrimaryPrimaryMemoryMemory

Program1.class

Editor

Compiler

Class Loader

Byte Code Verifier

..

..

..

Interpreter

..

..

..

..

..

..

Java Program TypesJava Program Types

Console and Windowed applicationsAppletsServletsWeb ServicesJavaBeans

Console ApplicationsConsole Applications

Stand-alone programs using a command-line interface

Windowed ApplicationsWindowed Applications

Stand-alone programs using a graphical user interface (GUI)

AppletsApplets

Client-side programs executed as part of a displayed Web page

ServletsServlets

Server-side programs hosted and run on a Web server

Used in conjunction with Java Server Pages (JSP) to provide sophisticated server-side logic

Enable connections to server databases through Java Database Connectivity (JDBC)

ServletsServlets

Web ServicesWeb ServicesServices receive information

requests over the Web and return the requested data

JavaBeansJavaBeansReusable software components

Sample ProblemSample Problem

A programmer needs an algorithm to determine an employee’s weekly wages. How would the calculations be done by hand?

One Employee’s WagesOne Employee’s Wages

In one week an employee works 52 hours at the hourly pay rate of $24.75. Assume a 40.0 hour normal work week and an overtime pay rate factor of 1.5

What are the employee’s wages?40 x $ 24.75 = $ 990.00

12 x 1.5 x $ 24.75 = $ 445.50___________

$ 1435.50

If hours are more than 40.0, then

wages = (40.0 * payRate) + (hours - 40.0) * 1.5 *payRate

otherwise,

wages = hours * payRate

Weekly Wages, in GeneralWeekly Wages, in General

RECALL EXAMPLE

( 40 x $ 24.75 ) + ( 12 x 1.5 x $ 24.75 ) = $1435.50

An Algorithm is . . .An Algorithm is . . .

a step-by-step procedure for solving a problem in a finite amount of time.

Algorithm to Determine an Algorithm to Determine an Employee’s Weekly WagesEmployee’s Weekly Wages

1. Display to the screen “how many hours did you work?” 2. Input hours 3. Display to the screen “what is your rate of pay?” 4. Input rate 5. Calculate this week’s regular wages 6. Calculate this week’s overtime wages (if any) (Fill in details of how to do steps 5 and 6) 7. Add the regular wages to overtime wages (if any) to determine

total wages for the week

Translating your algorithm into a programming language is called CODING

The “code” or “program” for this algorithm is on the next screen

// A payroll program public class Payroll{ public static void main(String [] args) { double hours, rate, regularPay, overtimePay,grossPay; Scanner keyboard = new Scanner(System.in); System.out.print( "How many hours did you work?“) ; hours = keyboard.nextInt(); System.out.print( "how much were you paid per hour?“); rate = keyboard,nextInt(); if (hours <= 40) { regularPay = hours * rate; overtimePay = 0.0; } else { regularPay = 40 * rate; overtimePay = (hours - 40 ) * (rate * 1.5 ); } grossPay = regularPay + overtimePay; System.out.println(“Your gross pay is” + grossPay);

} }

Introduction to Object-oriented Introduction to Object-oriented Programming and DesignProgramming and Design

Key concepts in beginning to Key concepts in beginning to understand object-oriented understand object-oriented programmingprogramming

A specific approach to programmingData and operations on the data are

packaged together into a single unit called an object.

Models real-world problems

OBJECT ORIENTED OBJECT ORIENTED PROGRAMMINGPROGRAMMING

What is an object?

A noun

A person

A bank account

A rectangle

A grade book

What is an object’s data members?What is an object’s data members?

Person

A name

An address

A phone number

A social security number

What is an object’s behavior?What is an object’s behavior?

Person

Eats

Drinks

Walks

Exercises

In order to eat, does the person object need anything?

Food

Utensils

Rather than describing every single person, in object-oriented programming, the programmer describes a general type of an object and then creates many of the objects of that same type.

The person classThe person classclass Person{ // data members name; address; phonenumber; socialno; hand; mouth; // methods (behaviors) void eat(good food, fork utensils) { hand = utensils; mouth = food; }

Create many objects of type Person:

Person Judy;

Person John;

Person Ann;

Creating a new class from an Creating a new class from an existing classexisting class

class Instructor extends Person{ // Instructor gets to use all of Person data members // and methods // Instructor’s data members textbooks; computer; // Instructor’s methods void teach(….. ) { ……. };// other stuff }

Test your understanding on an Test your understanding on an airline reservation systemairline reservation system

What would some of the objects be?What data would the object contain?What operations would be performed

on that data?

Conclusion of Class 3Conclusion of Class 3