For Example,

This is Demo.
his is Demo.T
is is Demo.Th
…

How to write program for this?

1. We need applet first. Will follow the applet life cycle

   import java.applet.*;
   import java.awt.*;
   
   public class bannerDemo extends Applet
   {
   	public void init()
   	{
   	}
   	public void paint(Graphics g)
   	{
   	}		
   }
   /*
   <applet code="bannerDemo" width="500" height="150"></applet>
   */
   

2. We want to draw a String on applet area. Which can be done by calling drawString() method of Graphics class inside paint() method.

   	public void paint(Graphics g)
   	{
   		Font f = new Font("Arial",Font.BOLD,36);
   		g.setFont(f);
   		g.drawString("Ankit Virparia (ankit.co)",50,75);
   	}	
   

3. We want continuous change in the text which we have printed so, Will go for multithreading.

   public class bannerDemo extends Applet implements Runnable
   {
   	Thread t;
           public void run()
   	{}
   }
   

4. Here one extra thread will be given a responsibility to update the text given (which is stored in a global variable – I mean common between paint() and run() methods)

   public class bannerDemo extends Applet implements Runnable
   {
   	Thread t;
   	String msg = "Ankit Virparia (ankit.co)";
   	
   	public void run()
   	{
   		try
   		{
   			while(true)
   			{
   				t.sleep(1000);
   				char c = msg.charAt(0);
   				String tmp = msg.substring(1,msg.length());
   				msg = tmp + c;
   				repaint();
   			}
   		}
   		catch(Exception e)
   		{
   			System.out.println(e);	
   		}
   	}
   		
   	public void paint(Graphics g)
   	{
   		Font f = new Font("Arial",Font.BOLD,36);
   		g.setFont(f);
   		g.drawString(msg,50,75);
   	}	
   	
   }
   

5. We need to start the thread in the beginning. Which can be written in init() method.

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

6. paint() is invoked only when a user does GUI related change. But here in our case we want to invoke paint() at the interval of 1 second.

7. We are ready to go!

Program for Banner Applet

File Name:bannerDemo.java

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

public class bannerDemo extends Applet implements Runnable
{
	Thread t;
	String msg = "Ankit Virparia (ankit.co)";
	public void init()
	{
		t = new Thread(this);
		t.start();
	}
	
	public void run()
	{
		try
		{
			while(true)
			{
				t.sleep(1000);
				char c = msg.charAt(0);
				String tmp = msg.substring(1,msg.length());
				msg = tmp + c;
				repaint();
			}
		}
		catch(Exception e)
		{
			System.out.println(e);	
		}
	}
		
	public void paint(Graphics g)
	{
		Font f = new Font("Arial",Font.BOLD,36);
		g.setFont(f);
		g.drawString(msg,50,75);
	}	
	
}

/*
<applet code="bannerDemo" width="500" height="150"></applet>
*/

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