/**
  * Draws a ball bouncing around
  */
 import java.applet.*;
 import java.awt.*;
 import javax.swing.*;
 
 public class ball extends Applet implements Runnable {
     int x_pos = 10;
 
     int y_pos = 100;
 
     int radius = 20;
 
     private Image image;
 
     private Graphics graphic;
 
     public void init() {
         setBackground(Color.blue);
     }
 
     public void start() {
         Thread th = new Thread( /* this*/this);
         th.start();
     }
 
     public void stop() {
     }
 
     public void destroy() {
     }
 
     public void run() {
         Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
         while ( true ) {
             x_pos++;
             repaint();
             try {
                 Thread.sleep(20);
             }
             catch (InterruptedException ie) {
             }
             Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
         }
     }
 
     public void paint(Graphics g) {
         g.setColor(Color.red);
         g.fillOval(x_pos - radius, y_pos - radius, 2 * radius, 2 * radius);
     }
 
     public void update(Graphics g) {
         // initialize buffer
         if ( image == null ) {
             image = createImage(this.getSize().width, this.getSize().height);
             graphic = image.getGraphics();
         }
         // clear screen in background
         graphic.setColor(getBackground());
         graphic.fillRect(0, 0, this.getSize().width, this.getSize().height);
         // draw elements in background
         graphic.setColor(getForeground());
         paint(graphic);
         // draw image on the screen
         g.drawImage(image, 0, 0, this);
     }
 }