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Java applet

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Rohan Gajre
Rohan Gajre

This document provides an introduction and overview of Java applet programming. It discusses what Java and applets are, the applet skeleton structure including common lifecycle methods like init(), start(), paint(), stop(), and destroy(). It also outlines the steps to write an applet code, compile it, and include it in an HTML file using applet tags to display the applet. An example Java applet class and HTML code is provided at the end to demonstrate a simple "Hello World" style applet.

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Java Applet Programming Rohan K. Gajre.
Outline • Introduction to java Programming • Applet Overview • Applet Skeleton • Steps to Write Applet Code • Compilation Process • Java Applet E.g. with HTML Code
What is Java • Java is Simplified version of C++ • Java is a programming language that is object Oriented and specifically designed to have as few implementation dependencies as possible • Java Programs can be easily moved form one computer to another • Almost everything in Java is an Object and Classes • Java has the ability to share both data and program • Java does not use pointer and header files • A class is collection of Object of similar type
What is Applet • Applet are Java Program that are used for Internet Computing • Applet can be transported over the internet from one computer to another • It can perform logical and arithmetic operations as well as accept user input • Applet are event driven • If you want to write applet code so you need to import two packages that is awt(Abstract Window Toolkit) and applet
Cont. • Execution of applet code does not begin with main()function • Types of Applet Local Applet :- Developed & stored in Local System Remote Applet :- Developed & stored on a Remote computer connected to the internet • Once an applet has been compiled, it is included in an HTML file using Applet tag
Cont. • Applets are not executed by a console based java run-time interpreter, but they are executed by either a java enabled web browser or an applet viewer. • You need two notepad one for java(Applet)code and another for HTML code having Applet Tag in that
An Applet Skeleton • Applet skeleton includes different methods for writing applet • When an applet begins, the AWT calls the following methods, in this sequence: init( ) start( ) paint( ) • When an applet is terminated, the following sequence of method calls takes place:
Cont. • stop( ) • destroy( ) • Above all methods are in Applet Life cycle • Explanation about above is as follows: • init( ):- init() is the first method to be called. This is where you should initialize variables. This method is called only once during run time of your applet
Cont. • start( ):- start() called after init(), also called to restart applet after it has been stopped. start() is called each time an applet’s HTML document is displayed on screen. • paint( ):- paint() is called each time your applets output must be redrawn. also called when the applet begins execution. This method has one parameter, Graphics. • stop( ):- stop()is called when a web browser leaves the HTML document containing the applet- when it goes to another page.
Cont. • destroy( ) :- destroy() is called when environment determines that your applet needs to be removed completely from memory. The stop() method is always called before destroy().
Steps to write Applet code • Writing an applet code in java file & save with class name (.java file) • Compile it & create (.class file) • Design a page using HTML tags • Write a <APPLET> Tag in that • Save it same as a class name with .HTML extension • Testing
Compilation Process • Open command prompt then go to directory using CD command • E.g. c:Users>d: • I am in D Drive now going to my directory using CD command • D:> cd Ram • I am in my directory that is Ram • Compile source file D:Ram> Javac Classname.java • E.g. D:Ram> Javac Demo.java
Cont. • Open file in appletviewer • Then Run HTML code • D:Ram> appletviewer classname.html • E.g. D:Ram> appletviewer Demo.html
Following Program shows a simple java applet import java.applet.*; import java.awt.*; public class DemoApp extends Applet{ public void paint (Graphics g) { g.drawString (“Welcome in Applet World", 25, 50); } }
Cont. • Save source file with name DemoApp.java • Compile source file D:Ram> javac DemoApp.java • Write HTML File and save it DemoApp.html
HTML Code <html> <title> Welcome in Applet World </title> <hr> <applet code=“DemoApp.class" width="320" height="120"> </applet> </hr> </html>
Cont. • Open file in appletviewer • Then Run HTML code • D:Ram> appletviewer DemoApp.html
Java applet

More Related Content

Java applet

  • 2. Outline • Introduction to java Programming • Applet Overview • Applet Skeleton • Steps to Write Applet Code • Compilation Process • Java Applet E.g. with HTML Code
  • 3. What is Java • Java is Simplified version of C++ • Java is a programming language that is object Oriented and specifically designed to have as few implementation dependencies as possible • Java Programs can be easily moved form one computer to another • Almost everything in Java is an Object and Classes • Java has the ability to share both data and program • Java does not use pointer and header files • A class is collection of Object of similar type
  • 4. What is Applet • Applet are Java Program that are used for Internet Computing • Applet can be transported over the internet from one computer to another • It can perform logical and arithmetic operations as well as accept user input • Applet are event driven • If you want to write applet code so you need to import two packages that is awt(Abstract Window Toolkit) and applet
  • 5. Cont. • Execution of applet code does not begin with main()function • Types of Applet Local Applet :- Developed & stored in Local System Remote Applet :- Developed & stored on a Remote computer connected to the internet • Once an applet has been compiled, it is included in an HTML file using Applet tag
  • 6. Cont. • Applets are not executed by a console based java run-time interpreter, but they are executed by either a java enabled web browser or an applet viewer. • You need two notepad one for java(Applet)code and another for HTML code having Applet Tag in that
  • 7. An Applet Skeleton • Applet skeleton includes different methods for writing applet • When an applet begins, the AWT calls the following methods, in this sequence: init( ) start( ) paint( ) • When an applet is terminated, the following sequence of method calls takes place:
  • 8. Cont. • stop( ) • destroy( ) • Above all methods are in Applet Life cycle • Explanation about above is as follows: • init( ):- init() is the first method to be called. This is where you should initialize variables. This method is called only once during run time of your applet
  • 9. Cont. • start( ):- start() called after init(), also called to restart applet after it has been stopped. start() is called each time an applet’s HTML document is displayed on screen. • paint( ):- paint() is called each time your applets output must be redrawn. also called when the applet begins execution. This method has one parameter, Graphics. • stop( ):- stop()is called when a web browser leaves the HTML document containing the applet- when it goes to another page.
  • 10. Cont. • destroy( ) :- destroy() is called when environment determines that your applet needs to be removed completely from memory. The stop() method is always called before destroy().
  • 11. Steps to write Applet code • Writing an applet code in java file & save with class name (.java file) • Compile it & create (.class file) • Design a page using HTML tags • Write a <APPLET> Tag in that • Save it same as a class name with .HTML extension • Testing
  • 12. Compilation Process • Open command prompt then go to directory using CD command • E.g. c:Users>d: • I am in D Drive now going to my directory using CD command • D:> cd Ram • I am in my directory that is Ram • Compile source file D:Ram> Javac Classname.java • E.g. D:Ram> Javac Demo.java
  • 13. Cont. • Open file in appletviewer • Then Run HTML code • D:Ram> appletviewer classname.html • E.g. D:Ram> appletviewer Demo.html
  • 14. Following Program shows a simple java applet import java.applet.*; import java.awt.*; public class DemoApp extends Applet{ public void paint (Graphics g) { g.drawString (“Welcome in Applet World", 25, 50); } }
  • 15. Cont. • Save source file with name DemoApp.java • Compile source file D:Ram> javac DemoApp.java • Write HTML File and save it DemoApp.html
  • 16. HTML Code <html> <title> Welcome in Applet World </title> <hr> <applet code=“DemoApp.class" width="320" height="120"> </applet> </hr> </html>
  • 17. Cont. • Open file in appletviewer • Then Run HTML code • D:Ram> appletviewer DemoApp.html