import java.awt.*;import java.awt.event.*;import javax.swing.*;public class BounceExpress{  public static void main(String[] args)   {  JFrame frame = new BounceExpressFrame();      frame.show();   }}class BounceExpressFrame extends JFrame{  public BounceExpressFrame()   {  setSize(300, 200);      setTitle("Bounce");      addWindowListener(new WindowAdapter()         {  public void windowClosing(WindowEvent e)            {  System.exit(0);            }         } );      Container contentPane = getContentPane();      canvas = new JPanel();      contentPane.add(canvas, "Center");      JPanel p = new JPanel();      addButton(p, "Start",         new ActionListener()         {  public void actionPerformed(ActionEvent evt)            {  for (int i = 0; i < 5; i++)               {  Ball b = new Ball(canvas, Color.black);                  b.setPriority(Thread.NORM_PRIORITY);                  b.start();               }            }         });      addButton(p, "Express",         new ActionListener()         {  public void actionPerformed(ActionEvent evt)            {  for (int i = 0; i < 5; i++)               {  Ball b = new Ball(canvas, Color.red);                  b.setPriority(Thread.NORM_PRIORITY + 2);                  b.start();               }            }         });      addButton(p, "Close",         new ActionListener()         {  public void actionPerformed(ActionEvent evt)            {  canvas.setVisible(false);               System.exit(0);            }         });      contentPane.add(p, "South");   }   public void addButton(Container c, String title,      ActionListener a)   {  JButton b = new JButton(title);      c.add(b);      b.addActionListener(a);   }   private JPanel canvas;}class Ball extends Thread{  public Ball(JPanel b, Color c) { box = b; color = c; }   public void draw()   {  Graphics g = box.getGraphics();      g.setColor(color);      g.fillOval(x, y, XSIZE, YSIZE);      g.dispose();   }   public void move()   {  if (!box.isVisible()) return;      Graphics g = box.getGraphics();      g.setXORMode(box.getBackground());      g.setColor(color);      g.fillOval(x, y, XSIZE, YSIZE);      x += dx;      y += dy;      Dimension d = box.getSize();      if (x < 0)      { x = 0; dx = -dx; }      if (x + XSIZE >= d.width)      { x = d.width - XSIZE; dx = -dx; }      if (y < 0)      { y = 0; dy = -dy; }      if (y + YSIZE >= d.height)      { y = d.height - YSIZE; dy = -dy; }      g.fillOval(x, y, XSIZE, YSIZE);      g.dispose();   }   public void run()   {  try      {  draw();         for (int i = 1; i <= 1000; i++)         {  move();            sleep(5);         }      }      catch(InterruptedException e) {}   }   private JPanel box;   private static final int XSIZE = 10;   private static final int YSIZE = 10;   private int x = 0;   private int y = 0;   private int dx = 2;   private int dy = 2;   private Color color;}