Short Guide to Java Applet Programming


Revision 1.1

August 01, 2010



by

Aloysius Indrayanto



(C) 2010 AnemoneSoft.com


This document is multi-licensed under the Creative Commons Attribution Share-Alike (CC-BY-SA) license version 3.0 and the GNU Free Documentation License (GNU FDL) version 1.3 or later.



1. Introduction

Java is a programing language that has a similar syntax with C/C++. However, unlike C/C++, it has a simpler object model and fewer low-level functionality. Java was originally developed by James Gosling at Sun Microsystems (which is now a subsidiary of Oracle Corporation). The first version of Java was released in 1995. Java applications are compiled into bytecode and meant to be run on a Java Virtual Machine (JVM). The same bytecode can be run on any JVM that complies with the Java implementation standard. Hence, Java applications can be run in any platform and operating system that are supported by the JVM. Java installation package basically comes in two big flavors:

In May 2007, Sun released most of its Java technologies under the GNU General Public License. Java standard is now controlled through the Java Community Process.

The word “applet” usually refers to a small application that performs a specific task. However, it can also refer to an application which is embedded in another application to enhance the main application. An applet can run as an independent application as well as within the context of a larger application. The word applet was most likely first used by the scripting language AppleScript in year 1993.

A Java applet is a Java bytecode which is embedded in an HTML page. A Java applet can run in a web browser using a JVM or in an AppletViewer (a stand-alone tool for testing applets). Java applets were introduced from the very first version of Java in 1995. Java applets are usually developed by using the Java programing language. However, it is also possible to use other languages (such as Jython, Ruby, and Eiffel) that compile into standard-compliant Java bytecode. Some advantages of a Java applet are listed below:

Some disadvantages of a Java applet are listed below:

Please refer to the appendix for the methods to install Java plugin for FireFox and SeaMoneky in Linux. Other browsers (at least Google Chrome and Opera) seem to be able to find the plugin automatically, copy the settings from FireFox, or even provide a GUI interface to select/find the appropriate plugin. In Windows, FireFox should be able to automatically find the Java plugin from the installed JRE.

2. Requirements

A basic knowledge in programming using Java will be needed to understand the topic discussed in this tutorial. A system with an installation of Apache Web Server (HTTPD) version 2.2.x, Java Development Kit (JDK) version 1.6.x (Java Standard Edition 6), and a recent enough browser that can execute Java applet will be needed to run the code snippets.

3. “Hello World” Applet

The code snippet below shows a simple example of how to embed a Java applet in an HTML page.

<!DOCTYPE html PUBLIC '-//W3C//DTD XHTML 1.0 Strict//EN'  
                      'http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd'>

<html xmlns='http://www.w3.org/1999/xhtml' lang='en' xml:lang='en'>

    <head></head>

    <body>
        <applet width='320' height='240' codebase='HelloWorld/' code='HelloWorld.class'>
        </applet>
    </body>

</html>

tut01.html

The codebase attribute basically specify the CLASSPATH of the Java applet. In the example above, all the Java classes will be inside the 'HelloWorld' directory which is under the directory that contains the HTML file. The code attribute specify the main class of the applet (the class to be executed). The code snipped below shows the source code of the applet. Remember that a Java source file must has the same name with the public class defined in it.

import java.applet.*;
import java.awt.*;

public class HelloWorld extends Applet {
    // To suppress warning message
    private static final long serialVersionUID = 1L;

    // Size of the applet
    private int _width, _height;

    // Initialize the applet
    public void init()
    {
        _width  = getSize().width;
        _height = getSize().height;
        setBackground(Color.black);
    }

    // Draw the content of the applet
    public void paint(Graphics g)
    {
        g.setColor(Color.green);
        g.drawString("Hello world from Java Applet!", 50, 50);
    }
}

HelloWorld.java

Compile the code using the command 'javac -Xlint HelloWorld.java'. The resulting class file 'HelloWorld.class' will be stored in the same directory. When executed in a browser, the output would be similar to:

It is recommended to configure the JDK/JRE to always show the Java console when running an applet (please refer to the appendix). The console can be used to display exception messages, reset the JRE cache, etc. The picture below shows a typical Java console.


Explanation:

It is possible to develop an applet's main class that can also be run as a stand-alone Java application. This approach can be useful if a developer wants to develop a small utility that needs to be run both from the web and as a local application. However, for online game development, this approach may be not a good idea because it may add unnecessary complication as well as reducing the maintainability and security of the application. The code snippet below shows the needed modifications to the previous code snippet to make it capable of being run as a stand-alone Java application. Note that the applet's main class has been renamed to HelloWorldST.

import java.applet.*;
import java.awt.*;
import java.awt.event.*;

import java.net.URL;
import java.net.MalformedURLException;

class HelloWorldST_AppletStub implements AppletStub {
    private Applet _applet;

    public HelloWorldST_AppletStub(String argv[], Applet a)
    { _applet = a; }

    public void appletResize(int width, int height)
    { _applet.resize(width, height); }

    public AppletContext getAppletContext()
    { return null; }

    public java.net.URL getCodeBase()
    {
        try { return new URL("file://"); }
        catch(MalformedURLException e) { return null; }
    }

    public java.net.URL getDocumentBase()
    { return getCodeBase(); }

    public String getParameter(String p)
    { return null; }

    public boolean isActive()
    { return true; }
}

public class HelloWorldST extends Applet {
    ...
    ...
    ...

    // To indicate if the applet has ben run as a stand-alone Java application
    private static boolean _standAlone = false;


    ...
    ...
    ...

    // Draw the content of the applet
    public void paint(Graphics g)
    {
        g.setColor(Color.green);
        if(_standAlone)
            g.drawString("Hello world from Java!", 50, 50);
        else
            g.drawString("Hello world from Java Applet!", 50, 50);
    }

    // This main() method allows the applet to be run as a stand-alone Java application
    static public void main (String argv[])
    {
        // Size of the applet
        final int WIDTH  = 320;
        final int HEIGHT = 240;

        // Instantiate the applet and applet-stub class
        final Applet     applet     = new HelloWorldST();
        final AppletStub appletStub = new HelloWorldST_AppletStub(argv, applet);
        applet.setStub(appletStub);
        appletStub.appletResize(WIDTH, HEIGHT);

        // Generate a top-level frame to contain the applet
        Frame frame = new Frame("Hello World");
        frame.addWindowListener(
            new WindowAdapter()
            {
                // Ensure the applet is uninitialized if the frame is closed
                public void windowClosing(WindowEvent event)
                {
                    applet.stop();
                    applet.destroy();
                    System.exit(0);
                }
            }
        );

        // Show the frame
        frame.setResizable(false);
        frame.setVisible(true);

        // Get the frame's insets
        final Insets fi = frame.getInsets();
        final int    wo = fi.left + fi.right;
        final int    ho = fi.top + fi.bottom;

        // Set the frame's initial position and the frame's size
        frame.setBounds(50, 50, WIDTH + wo, HEIGHT + ho);

        // Add the applet to the frame and start the applet
        frame.add("Center", applet);
        _standAlone = true;
        applet.init();
        applet.start();
    }
}

HelloWorldST.java

Explanation:

The applet above can be run as a stand-alone application by using the command 'java HelloWorldST'. The result would be similar to the pictures below.

    

An applet can accept parameters from the HTML page by using the <param/> tag. It is possible to write a better applet stub class so that one can pass parameters from the command line in case the applet is executed as a stand-alone application. The modified applet stub class is shown below.

class HelloWorldST_Ex_AppletStub implements AppletStub {
    private Applet                    _applet;
    private Hashtable<String, String> _parameters;

    public HelloWorldST_Ex_AppletStub(String argv[], Applet a)
    {
        _applet = a;

        _parameters = new Hashtable<String, String>();
        for(int i = 0; i < argv.length; ++i) {
            try {
                StringTokenizer parser = new StringTokenizer(argv[i], "=");
                String name  = parser.nextToken().toString();
                String value = parser.nextToken("\"").toString().substring(1);
                _parameters.put(name, value);
            }
            catch(NoSuchElementException e) {}
        }
    }

    public void appletResize(int width, int height)
    { _applet.resize(width, height); }

    public AppletContext getAppletContext()
    { return null; }

    public java.net.URL getCodeBase()
    {
        try { return new URL("file://"); }
        catch(MalformedURLException e) { return null; }
    }

    public java.net.URL getDocumentBase()
    { return getCodeBase(); }

    public String getParameter(String p)
    { return _parameters.get(p); }

    public boolean isActive()
    { return true; }
}

4. Animation in Java Applet – “Bouncing Ball” Applet

The code snippets below show a simple example of how to implement animation with double buffering in Java applet.

<!DOCTYPE html PUBLIC '-//W3C//DTD XHTML 1.0 Strict//EN'  
                      'http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd'>

<html xmlns='http://www.w3.org/1999/xhtml' lang='en' xml:lang='en'>

    <head></head>

    <body>
        <applet width='320' height='240' codebase='BouncingBall/' code='BouncingBall.class'>
        </applet>
    </body>

</html>

tut02.html 


import java.applet.*;
import java.awt.*;

public class BouncingBall extends Applet implements Runnable {
    // To suppress warning message
    private static final long serialVersionUID = 1L;

    // Size of the applet
    private int _width, _height;

    // Backbuffer
    private Image    _bbImage;
    private Graphics _bbGraph;

    // Animation thread
    private Thread  _threadHandle    = null;
    private boolean _threadSuspended = false;

    // Animation data
    private int _xPos = 10, _xSpd =  5;
    private int _yPos = 10, _ySpd =  5;

    // Initialize the applet
    public void init()
    {
        _width  = getSize().width;
        _height = getSize().height;
        setBackground(Color.black);

        _bbImage = createImage(_width, _height);
        _bbGraph = _bbImage.getGraphics();
    }

    // Start the applet
    public void start()
    {
        // Create the thread if it is not yet exist
        if(_threadHandle == null) {
            _threadHandle    = new Thread(this);
            _threadSuspended = false;
            _threadHandle.start();
        }
        // Resume the thread if it is currently suspended
        else if(_threadSuspended) {
            _threadSuspended = false;
            synchronized(this) {
                notify();
            }
        }
    }

    // Stop the applet
    public void stop()
    { _threadSuspended = true; }

    // Draw the content of the applet
    public void paint(Graphics g)
    { update(g); }

    // Update the content of the applet
    public void update(Graphics g)
    { g.drawImage(_bbImage, 0, 0, this); }

    // Thread procedure
    public void run()
    {
        try {
            while (true) {
                // Check if the thread should suspend itself
                if(_threadSuspended) {
                    synchronized(this) {
                        while(_threadSuspended) wait();
                    }
                }
                // Draw the ball
                _bbGraph.setColor(Color.black);
                _bbGraph.fillRect(0, 0, _width, _height);
                _bbGraph.setColor(new Color(0,  64, 0));
                _bbGraph.fillOval(_xPos    , _yPos    , 20, 20);
                _bbGraph.setColor(new Color(0, 128, 0));
                _bbGraph.fillOval(_xPos + 2, _yPos + 2, 16, 16);
                _bbGraph.setColor(new Color(0, 207, 0));
                _bbGraph.fillOval(_xPos + 4, _yPos + 4, 12, 12);
                _bbGraph.setColor(new Color(0, 255, 0));
                _bbGraph.fillOval(_xPos + 6, _yPos + 6,  8,  8);
                // Update the ball's position
                _xPos += _xSpd;
                _yPos += _ySpd;
                if(_xPos <            0) { _xPos =            0; _xSpd = -_xSpd; }
                if(_xPos > _width  - 20) { _xPos = _width  - 20; _xSpd = -_xSpd; }
                if(_yPos <            0) { _yPos =            0; _ySpd = -_ySpd; }
                if(_yPos > _height - 20) { _yPos = _height - 20; _ySpd = -_ySpd; }
                // Repaint and sleep
                repaint();
                _threadHandle.sleep(50);
            }
        }
        catch(InterruptedException e) {}
    }
}

BouncingBall.java

Compile the code using the command 'javac -Xlint BouncingBall.java'. The result would be similar to the picture below.

Explanation:

4.1. Adding Sound Effect

All unsigned applets cannot access local files. Therefore from this section onwards, you will need to host the HTML and applet classes in a web server. It is recommended to always use a local (personal) web server when developing an applet-based application so that one can be sure that the applet will be executed as if it is in a real deployment environment (the internet).

The first step to add sound effects is to create an audio player class that utilizes features from javax.sound.sampled. However, it is important to understand that the current Java sound library (Java Standard Edition 6) has some limitations:

The code snippet below shows a simple audio player class that can only play audio files which are encoded in plain PCM (Pulse-Code Modulation). The method to write a custom mixer will not be discussed in this tutorial.

class AudioPlayer implements Runnable {
    private static final int INIT_BUFFER_SIZE = 1024 *  16;
    private static final int READ_BUFFER_SIZE = 1024 * 128;

    private byte[]        _buff  = null;
    private Mixer         _mixer = null;
    private AudioFormat   _af    = null;
    private DataLine.Info _dli   = null;
    private Thread        _th    = null;

    public AudioPlayer(String urlAudio)
    {
        try {
            // Open the audio
            URL               url = new URL(urlAudio);
            AudioInputStream  ais = AudioSystem.getAudioInputStream(url.openStream());

            // Get mixer, format, and data line
            _mixer = AudioSystem.getMixer(null);
            _af    = ais.getFormat();
            _dli   = new DataLine.Info(SourceDataLine.class, _af);

            // Allocate the initial audio buffer
            _buff = new byte[INIT_BUFFER_SIZE];

            // Read the audio data
            byte[] readBuff = new byte[READ_BUFFER_SIZE];
            int    totCount = 0;
            while(true) {
                // Read and check for end of stream
                int readCount = ais.read(readBuff, 0, readBuff.length);
                if(readCount <= 0) break;
                // Resize the audio buffer (if needed)
                if(totCount + readCount > _buff.length) {
                    // Allocate a new buffer
                    byte[] newBuff = new byte[_buff.length +
                                              Math.max(INIT_BUFFER_SIZE, readCount)];
                    // Copy data
                    System.arraycopy(_buff, 0, newBuff, 0, _buff.length);
                    // Swap buffer
                    _buff = newBuff;
                }
                // Copy data to the audio buffer
                System.arraycopy(readBuff, 0, _buff, totCount, readCount);
                totCount += readCount;
            }

            // Truncate the audio buffer to fit the full size of the audio stream
            if(totCount < _buff.length) {
                // Allocate a new buffer
                byte[] newBuff = new byte[totCount];
                // Copy data
                System.arraycopy(_buff, 0, newBuff, 0, totCount);
                // Swap buffer
                _buff = newBuff;
            }
        }
        catch(MalformedURLException e) {
            System.out.printf("MalformedURLException\n");
            System.out.printf("%s\n", e.getMessage());
        }
        catch(IOException e) {
            System.out.printf("IOException\n");
            System.out.printf("%s\n", e.getMessage());
        }
        catch(UnsupportedAudioFileException e) {
            System.out.printf("UnsupportedAudioFileException\n");
            System.out.printf("%s\n", e.getMessage());
        }
    }

    public void run()
    {
        SourceDataLine line = null;

        try {
            line = (SourceDataLine) _mixer.getLine(_dli);
            line.open(_af);
            line.start();
            line.write(_buff, 0, _buff.length);
            line.drain();
        }
        catch(LineUnavailableException e) {
            System.out.printf("LineUnavailableException\n");
            System.out.printf("%s\n", e.getMessage());
        }
        catch(Exception e) {
            System.out.printf("Exception\n");
            System.out.printf("%s\n", e.getMessage());
        }

        if(line != null) line.close();
        line = null;
        _th   = null;
    }

    public void play()
    {
        if(_buff.length <= 0 || _th != null) return;

        _th = new Thread(this);
        _th.start();
    }
}

Explanation:

The code snippet below shows the needed modifications to the original bouncing ball applet to make it capable of playing sound effect.

import java.applet.*;
import java.awt.*;

import java.lang.Math;

import java.net.URL;
import java.net.MalformedURLException;
import java.io.IOException;

import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.Mixer;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.SourceDataLine;
import javax.sound.sampled.UnsupportedAudioFileException;
import javax.sound.sampled.LineUnavailableException;

class AudioPlayer implements Runnable {
    ...
    ...
    ...
}

public class BouncingBallWS extends Applet implements Runnable {
    ...
    ...
    ...

    // Animation data
    private int         _xPos = 10;
    private int         _yPos = 10;
    private int         _xSpd =  5;
    private int         _ySpd =  5;
    private AudioPlayer _ap   = null;

    // Initialize the applet
    public void init()
    {
       _width    = getSize().width;
       _height   = getSize().height;
       _codeBase = getCodeBase().toString();

        setBackground(Color.black);

        _bbImage = createImage(_width, _height);
        _bbGraph = _bbImage.getGraphics();

        _ap = new AudioPlayer(_codeBase + "../cling.wav");
    }

    ...
    ...
    ...

    // Thread procedure
    public void run()
    {
        try {
            while (true) {
                ...
                ...
                ...

                // Update the ball's position and play audio (if needed)
                boolean pAud = false;
                _xPos += _xSpd;
                _yPos += _ySpd;
                if(_xPos <            0) { _xPos =            0; _xSpd = -_xSpd; pAud = true; }
                if(_xPos > _width  - 20) { _xPos = _width  - 20; _xSpd = -_xSpd; pAud = true; }
                if(_yPos <            0) { _yPos =            0; _ySpd = -_ySpd; pAud = true; }
                if(_yPos > _height - 20) { _yPos = _height - 20; _ySpd = -_ySpd; pAud = true; }
                if(pAud) _ap.play();
                // Repaint and sleep
                repaint();
                _threadHandle.sleep(50);
            }
        }
        catch(InterruptedException e) {}
    }
}

BouncingBallWS.java

Explanation:

4.2. Making It a Stand-Alone Application

It is quite simple to convert the previous code snippet so that it can be run both as an applet and as a stand-alone application. There are only three modifications that need to be done:

Please refer to 'HelloWorldST.java' for the details of the applet stub class and the main() method. The code snippet below shows the necessary modifications to the previous code snippet to make it capable of being run as a stand-alone Java application. Note that the applet's main class has been renamed to BouncingBallWSST.

class BouncingBallWSST_AppletStub implements AppletStub {
    ...
    ...
    ...
}

class AudioPlayer implements Runnable {
    ...
    ...
    ...

    public AudioPlayer(String locAudio)
    {
        try {
            // Open the audio
            URL               url = new URL(locAudio);
            AudioInputStream  ais = null;
            if(url.getProtocol() == "file")
                ais = AudioSystem.getAudioInputStream(new File(url.getPath()));
            else
                ais = AudioSystem.getAudioInputStream(url.openStream());

    ...
    ...
    ...
}

public class BouncingBallWSST extends Applet implements Runnable {
    ...
    ...
    ...

    // To indicate if the applet has ben run as a stand-alone Java application
    private static boolean _standAlone = false;

    ...
    ...
    ...

    // This main() method allows the applet to be run as a stand-alone Java application
    static public void main (String argv[])
    {
        ...
        ...
        ...

        // Generate a top-level frame to contain the applet
        Frame frame = new Frame("Bouncing Ball");
        ...
        ...
        ...
    }
}

BouncingBallWSST.java

The result would be similar to the picture below.

4.3. Playing Ogg Vorbis and MP3 Audio

Playing Ogg Vorbis and MP3 audio streams have been made easy by using plugins/libraries from http://www.tritonus.org/plugins.html and http://www.jcraft.com/jorbis. The code snippet below shows the necessary modification to the AudioPlayer class so that it can load compressed audio stream. The name of the audio file is now also obtained from the clingAudioFile applet parameter.

    ...
    ...
    ...

    public AudioPlayer(String urlAudio)
    {
        try {
            // Open the audio
            URL               url = new URL(urlAudio);
            AudioInputStream  sis = AudioSystem.getAudioInputStream(url.openStream());
            AudioFormat       sfm = sis.getFormat();

            // Get mixer, format, and data line
            _mixer = AudioSystem.getMixer(null);
            _af    = new AudioFormat(AudioFormat.Encoding.PCM_SIGNED,
                                     sfm.getSampleRate(), 
                                     16,                     // 16 bits per samples
                                     sfm.getChannels(), 
                                     sfm.getChannels() * 2,  // 16 bits are 2 bytes
                                     sfm.getSampleRate(), 
                                     false                   // Little endian
                                    );
            _dli   = new DataLine.Info(SourceDataLine.class, _af);

            // Convert the audio
            AudioInputStream ais = AudioSystem.getAudioInputStream(_af, sis);

            ...
            ...
            ...
     }

    ...
    ...
    ...

    public void init()
    {
        ...
        ...
        ...

        _ap = new AudioPlayer(_codeBase + getParameter("clingAudioFile"));
    }

    ...
    ...
    ...

BouncingBallWS_Decode.java

Decompressing/decoding a compressed audio format to plain PCM can simply be done by chaining two audio streams. The first one is used to read the audio data from the URL, the second one is used to convert (decompress/decode) the audio stream to the desired format.

The code snippets below demonstrate the usage of the archive attribute to load the needed libraries and the <param/> tag to define the name of the audio file. The libraries needed to play Ogg Vorbis audio files are a bit different than the libraries needed to play MP3 audio files.

<!DOCTYPE html PUBLIC '-//W3C//DTD XHTML 1.0 Strict//EN'
                      'http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd'>

<html xmlns='http://www.w3.org/1999/xhtml' lang='en' xml:lang='en'>

    <head></head>

    <body>
        <applet width    = '320'
                height   = '240'
                codebase = 'BouncingBallWS_Decode/'
                code     = 'BouncingBallWS_Decode.class'
                archive  = 'jorbis-0.0.17.jar,
                            tritonus_share-0.3.6.jar,tritonus_jorbis-0.3.6.jar'>
            <param name='clingAudioFile' value='../cling.ogg'/>
        </applet>
        <div>
            Using Ogg Vorbis plugin/library from<a href='http://www.tritonus.org/plugins.html'>
            http://www.tritonus.org/plugins.html</a> 
            and <a href='http://www.jcraft.com/jorbis/'>http://www.jcraft.com/jorbis</a>.
        </div>
    </body>

</html>

tut02ws_ovb.html 


<!DOCTYPE html PUBLIC '-//W3C//DTD XHTML 1.0 Strict//EN'
                      'http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd'>

<html xmlns='http://www.w3.org/1999/xhtml' lang='en' xml:lang='en'>

    <head></head>

    <body>
        <applet width    = '320'
                height   = '240'
                codebase = 'BouncingBallWS_Decode/'
                code     = 'BouncingBallWS_Decode.class'
                archive  = 'javalayer.jar,
                            tritonus_share-0.3.6.jar,tritonus_mp3-0.3.6.jar'>
            <param name='clingAudioFile' value='../cling.mp3'/>
        </applet>
        <div>
            Using MP3 plugin/library from<a href='http://www.tritonus.org/plugins.html'>
            http://www.tritonus.org/plugins.html</a>.
        </div>
    </body>

</html>

tut02ws_mp3.html

There seems to be bugs either in the libraries or in the JRE (or both). Only one audio format can be played by the same instance of JRE. If you run the Ogg Vorbis code snippet first and then run the MP3 code snippet, the second one will not run (it will produce error), and vice versa. One would need to restart the browser each time one wants to play different audio formats.

5. Using the <embed></embed> Tag

It is easy (and recommended) to replace the <applet></applet> tag with the newer <embed></embed> tag as shown in the code snippet below.

<!DOCTYPE html PUBLIC '-//W3C//DTD XHTML 1.0 Strict//EN'
                      'http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd'>

<html xmlns='http://www.w3.org/1999/xhtml' lang='en' xml:lang='en'>

    <head></head>

    <body>
        <embed type           = 'application/x-java-applet'
               width          = '320'
               height         = '240'
               codebase       = 'BouncingBallWS_Decode/'
               code           = 'BouncingBallWS_Decode.class'
               archive        = 'jorbis-0.0.17.jar,
                                 tritonus_share-0.3.6.jar,tritonus_jorbis-0.3.6.jar'
               pluginspage    = 'http://java.com/en/download/index.jsp'
               clingAudioFile = '../cling.ogg'>
        </embed>
        <div>
            Using Ogg Vorbis plugin/library from <a href='http://www.tritonus.org/plugins.html'> 
            http://www.tritonus.org/plugins.html</a>
            and <a href='http://www.jcraft.com/jorbis/'>http://www.jcraft.com/jorbis</a>.
        </div>
    </body>

</html>

tut02ws_ovb_embed.html

If an applet needs a specific version of JRE (for example Java Standard Edition 5), the type attribute can be extended to 'application/x-java-applet;version=1.5'. The pluginspage attribute should point to the URL from where users can download the needed plugin.

It is clear that using the <embed></embed> tag is a bit more complicated. However, it provides more features (the type and pluginspace attributes). The <embed></embed> tag is part of the new HTML 5 standard. Unless, there is a need to support very old browsers, using the <embed></embed> tag is strongly recommended. Try it for yourself to convert all the code snippets in this tutorial to use the <embed></embed> tag.



Appendix



====================================
Installing Java Plugin for x86 Linux
====================================

* For Firefox 2.0 or later and SeaMonkey 1.0 or later.
* Firefox 3.1 and later need JRE 1.6.0_10 or later.

-----------------
For Older Firefox
-----------------

Create a symbolic link to libjavaplugin_oji.so (located in the 'plugin/i386/ns7'
directory of your JRE installation) in your Mozilla plugins directory. Examples:

cd /usr/lib/firefox-3.6/plugins
ln -s /usr/java/jre1.6.0_20/plugin/i386/ns7/libjavaplugin_oji.so .

cd /usr/lib/firefox-3.6/plugins
ln -s /usr/java/jdk1.6.0_20/jre/plugin/i386/ns7/libjavaplugin_oji.so .

cd /usr/lib/firefox-3.6/plugins
ln -s /usr/java/latest/jre/plugin/i386/ns7/libjavaplugin_oji.so .

Please adjust the Firefox and Java plugins directories as needed.

-------------------------
For Firefox 3.1 and later
-------------------------

Create a symbolic link to libnpjp2.so (located in the 'lib/i386' directory
of your JRE installation) in your Mozilla plugins directory. Examples:

cd /usr/lib/firefox-3.6/plugins
ln -s /usr/java/jre1.6.0_20/lib/i386/libnpjp2.so .

cd /usr/lib/firefox-3.6/plugins
ln -s /usr/java/jdk1.6.0_20/jre/lib/i386/libnpjp2.so .

cd /usr/lib/firefox-3.6/plugins
ln -s /usr/java/latest/jre/lib/i386/libnpjp2.so .

Please adjust the Firefox and Java plugins directories as needed.


=======================================
Installing Java Plugin for x86_64 Linux
=======================================

* Available from JRE 1.6.0_12 or later.
* For Firefox 3.0 or later and pre-release versions of SeaMonkey 2.0.

Create a symbolic link to libnpjp2.so (located in the 'lib/amd64' directory
of your JRE installation) in your Mozilla plugins directory. Examples:

cd /usr/lib64/firefox-3.6/plugins
ln -s /usr/java/jre1.6.0_20/lib/amd64/libnpjp2.so .

cd /usr/lib64/firefox-3.6/plugins
ln -s /usr/java/jdk1.6.0_20/jre/lib/amd64/libnpjp2.so .

cd /usr/lib64/firefox-3.6/plugins
ln -s /usr/java/latest/jre/lib/amd64/libnpjp2.so .

Please adjust the Firefox and Java plugins directories as needed.


===========================================
Configuring Java to Always Show the Console
===========================================

* Run any of the commands:
/usr/java/jre1.6.0_20/bin/jcontrol
/usr/java/latest/bin/jcontrol
/usr/java/jdk1.6.0_20/bin/jcontrol

* Go to the 'Advanced' tab.

* Expand the 'Java Console' section.

* Select 'Show Console'.

* Click 'Apply' and then 'OK'.


References



http://en.wikipedia.org/wiki/Java_(programming_language), July 30, 2010

http://en.wikipedia.org/wiki/Java_Development_Kit, July 30, 2010

http://en.wikipedia.org/wiki/Java_applet, July 30, 2010

http://en.wikipedia.org/wiki/Applet, July 30, 2010

http://en.wikipedia.org/wiki/AppleScript, July 30, 2010

http://www.oracle.com/technetwork/java/index.html, July 30, 2010

http://download.oracle.com/javase/tutorial/java/index.html, July 30, 2010

http://profs.logti.etsmtl.ca/mmcguffin/learn/java, July 30, 2010