This document discusses JApplets, which are Java programs that are embedded in web pages. It explains that JApplets must extend the JApplet or Applet class and override certain methods. It also provides instructions for creating HTML files with applet tags to execute JApplets in a web browser or appletviewer application.

1. CS3135/CS2135
Object Oriented Programming (Java)
BSCS-3 / MCS-3
Lecture # 22
JApplet

2. JApplet
javax.swing.JApplet
• Applets are Java programs that are embedded in web pages. When a Java enabled web browser loads a web
page containing an applet, the applets downloads into the browser and executes.
• Java enabled web browsers contain Java Plugin. You can visit www.java.com whether your browser contain Java
Plugin or not. If not, you can click the Free Java Download button to install it.
• The application in which an applet executes is known as applet container. The JDK includes appletviewer applet
container for testing applets as you develop them and before you embed them in web page.
• Every Java applet must contain at least one public class declaration which also extends
Applet(java.applet.Applet)or JApplet(javax.swing.JApplet).
• Java applet must override methods init, start, paint, stop, destroy. If any of these methods are not declared
according to functionality, applet container calls their inherited empty body versions.
• After creating applet file having extension .java, create .htm or .html file which contains APPLET tag specifying
applet .class file and its path by code attribute. If both files are in same folder, no need to mention path.
• CODE contains only the name of the class file; CODEBASE contains an alternate pathname where classes are
contained. For example, if you store your class files in a directory called /classes, which is in the same directory
as your HTML files, CODEBASE is the following:
<APPLET CODE=”myclass.class” CODEBASE=”classes” WIDTH=100 HEIGHT=100>
</APPLET>
Instructor: Tanzila Kehkashan
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3. JApplet
Executing applet in appletviewer
• In command prompt, compile applet file with typical javac following command:
• javac filename.java
• In command prompt, execute html file by typing following command:
• appletviewer filename.html
Executing applet in web browser
• Right click on html file, open with Java enabled browser. Or
• Open browser. From file menu, open html file.
Enable Java in Web Browser
• Chrome versions launching since April 2015, do not support technology that run java in chrome.
• Run applets in Safari, Firefox, IE, etc.
• Before running applet, enable Java in your browser.
Internet Explorer
1. Click Tools and then Internet Options
2. Select the Security tab, and select the Custom Level
button
3. Scroll down to Scripting of Java applets
4. Make sure the Enable radio button is checked
5. Click OK to save your preference
Firefox
1. Open the Firefox browser or restart it, if it is already running
2. From the Firefox menu, select Tools, then click the Add-ons
option
3. In the Add-ons Manager window, select Plugins
4. Click Java (TM) Platform plugin to select it
5. Check that the option selected is Ask to Activate or Always
Activate or on older Firefox versions, click on the Enable
button (if the button says Disable, Java is already enabled)
Instructor: Tanzila Kehkashan
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4. JApplet
javax.swing.JApplet
• JApplet()
• Container getContentPane()
• void setJMenuBar(JMenuBar menuBar)
• void setLayout(LayoutManager manager)
• void update(Graphics g) // just calls paint method
Methods inherited from class java.applet.Applet
• void init()
• void start()
• AudioClip getAudioClip(URL url, String name)
• URL getDocumentBase()
Instructor: Tanzila Kehkashan
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5. Instructor: Tanzila Kehkashan
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6. Instructor: Tanzila Kehkashan
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7. Instructor: Tanzila Kehkashan
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