Tutorials : An Introduction to Multi-threading :

Extending the Thread class

import java.lang.*; 
//Note: The package java.lang is imported by default 
//in all java classes by the compiler

public class MyClass extends Thread 
{                      
    //Your code    
	public void run()                       
    {              
    	//Your code
    }
}

Implementing the Runnable Interface

import java.lang.*;
public class MyClass implements Runnable
{
        Thread t;
        //Your code
        public void run()                       
        {                              
         	//Your code            
        }
}

A Proper Example

The next line, t.start() is a method in the Thread. This indicates the runtime to get this thread to the run state (more on states later).

Notice that the code does not have a method called start(). When the threat starts executing, what actually happens in the background is: the runtime invokes the method containing the public void run() signature.

Note: The signature of the method is absolutely necessary. Without it, the default run() method from the Thread class will be executed and not the different method that you have written.

The run() method contains an implementation of a infinite for loop, which has the simple logic of string manipulation, a simple sleep of 500 ms, and also a call to the repaint() method.

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

/*
<applet code="AppletEx.class" height=100 width=100>
</applet>
*/

public class AppletEx extends Applet implements Runnable
{
	public String msg = "Hello. I'm Sridhar.";
	Thread t;

	public void init()
	{
		t = new Thread(this);
		t.start();
	}

	public void paint(Graphics g)
	{
		g.drawString(msg,10,10);
	}

	public void run()
	{
		for(;;)
		{
			char a = msg.charAt(0);
			msg = msg.substring(1,msg.length());
			msg = msg + a;
			try{
				Thread.sleep(500);
			}catch(Exception e)
			{}
		repaint();
		}
	}
}

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