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Java

• Teach Yourself Java : one of the best selling Java programing books
• WisdomSoft : introduction to Java language and Java API

Installation

$ sudo aptitude install sun-java6-jdk
$ sudo aptitude install sun-java6-plugin

If you want to have Sun's official tools as the default:

$ sudo update-java-alternatives -s java-6-sun

If you want to have the alternative open source tools as the default:

$ sudo update-java-alternatives -s java-6-openjdk

Otherwise, you can show interactive menu by just adding --config java to update-alternatives.

$ sudo update-alternatives --config java

If you need the Java API documentation,

$ sudo aptitude install openjdk-6-doc

and open file:///usr/share/doc/openjdk-6-doc/api/index.html with your favorite browser.

Java Notes

A class can only inherit one superclass:

class Foo extends Bar {
  private int balance;

  void deposit(int amount) {
    balance += amount;
  }
}

However, an interface can inherit multiple interfaces that are listed after the 'extends' keyword:

interface I1 extends I2, I3, I4, ... {
  int getWeight();
}

External Libraries

In Ubuntu and other Debian-based Linuxes, Java libraries are located in '/usr/share/java'. Mostly you can grab the packages with apt:

$ sudo aptitude install libjogl-java libjogl-java-doc

When you use an external library (i.e. some library that does not come with JDK), you need to tell where it is to the development tools.

You can do this by setting an environment variable called 'CLASSPATH', or giving an option to the tool like a compiler, just like in gcc there's an option '-L' to tell the compiler the location of the library to use.

You can set CLASSPATH environment variable with the current directory so that the tool searches in there, too. Jar files need to be specified as their file names.

$ export CLASSPATH=.:/usr/share/java/jogl.jar:/usr/share/java/gluegen-rt.jar

or use wildcard:

$ export CLASSPATH=.:/usr/share/java/*

Debian GNU/Linux uses this '/usr/share/java' path by default. Let's put this entry in the '~/.bash_profile' in your home.

AWT and Swing

• java.awt

• Event
• Event Source
• Event Listener

AWT is supported well under OpenGL. All you have to do is set up GLCanvas for rendering and giving commands to the GL library.

Probably if you've made GLCanvas to work, you'd love using it instead of GLJPanel that comes with Swing for the purported speed benefits.

Ant / Apache Projects

Ant : A build tool for Java similar to GNU make.

• Jakarta Project useful on site

HttpClient :

$ sudo aptitude install libcommons-httpclient-java
$ sudo aptitude install libcommons-httpclient-java-doc

$ CLASSPATH=$CLASSPATH:/usr/share/java/commons-httpclient.jar\\
:/usr/share/java/commons-logging.jar:/usr/share/java/commons-codec.jar

Multithreading

There are two ways to implement threads using Java standard Thread class in the class library.

class ThreadX extends Thread {
  public void run() {
    // Threaded code goes here...
  }
}

class Caller {
  public static void main(String args[]) {
    ThreadX th = new ThreadX();
    th.start();
    // th.join();
  }
}

class RunnableX implements Runnable {
  public void run() {
    // Threaded code goes here...
  }
}

class Caller {
  public static void main(String args[]) {
    RunnableX rx = new RunnableX();
    Thread th = new Thread(rx);
    th.start();
    // th.join();
  }
}

• synchronized

Frameworks

Server-side Frameworks

There are much more powerful frameworks in Java and JSP than ones for any other languages. However, Tomcat is not widely deployed to many web hosting services out there. So currently it will be better to use PHP if you want to spread your web application to general web service providers. These two languages resemble in some way as written above in Japanese:

By the way, JSP is a derivative of Java which embeds the code in an HTML file (like Smarty templates in PHP).

• Struts : the basic Java framework running on servlet container Tomcat
• Seasar

Client-side Frameworks

3D Engine Bindings

There are several kinds of 3D engine bindings for Java. One of which is Java3D that abstracts different APIs such as Direct3D and OpenGL. Java3D does not fully exploit the performance advantage of OpenGL, though its design is considerably affected by VRML.

When you use JOGL, pointers for vertices, colors and texture coords must point to direct buffers:

ByteBuffer data = ByteBuffer.allocateDirect(size);
...
data.position(0);
gl.glVertexPointer(3, GL.GL_FLOAT, 0, data);

• Java Gaming
• JOGL (an OpenGL binding for Java) is said to be faster in AWT than in Swing.
• OpenGL ES : OpenGL is for desktop as well as OpenGL ES for mobile devices and it can be set up this way . The binding for Java is called JSR239 and is a part of phoneME (Java MicroEdition) project.
• JSR239 : Java Binding for the OpenGL ES API
• Overview of Java Binding for the OpenGL ES API
• EGL

Have fun.