Bola Memantul Menggunakan Java

import java.util.*;
import java.util.Random;
import java.util.List;
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;

public class bolapantul extends JFrame implements Runnable
{

    private JPanel tempat          = new JPanel();
    private JPanel p1               = new JPanel();
    private JButton bMulai          = new JButton("Mulai/Tambah");
   
    Thread thread1 = new Thread(this);

    List listBola = Collections.synchronizedList(new ArrayList());

    public bolapantul()
    {
        p1.add(bMulai);
        getContentPane().add(tempat, "Center");
        getContentPane().add(p1, "South");

        setResizable(false);

        bMulai.addActionListener(new Kejadian());
            }
    public class Kejadian implements ActionListener
    {
        public void actionPerformed(ActionEvent e)
        {
            Object o  = e.getSource();
            String ac = e.getActionCommand();
            kelasBola bola = new kelasBola();
            if(o==bMulai)
            {
                listBola.add(bola);
                bola.start();
            }

                    }
    }

    public void run()
    {
        Image persegi = createImage(tempat.getWidth(), tempat.getHeight());
        Graphics g = persegi.getGraphics();
        Graphics gc = tempat.getGraphics();
        while (true)
            {
            g.setColor(Color.white);
            g.fillRect(0, 0, tempat.getWidth(), tempat.getHeight());
            synchronized (listBola)
            {
                for (Iterator i = listBola.iterator(); i.hasNext();)
                {
                    kelasBola b = (kelasBola)i.next();
                    b.draw(g);
                }
            }
            gc.drawImage(persegi, 0, 0, tempat);
            try {Thread.sleep(5);} catch(InterruptedException e)
            {
            }
        }
    }

    class kelasBola extends Thread implements Cloneable
    {
        private Random r;
        private boolean bulat=true;
        private boolean jalan=true;
        private Color color = Color.black;
        private int x = 0;
        private int y = 0;
        private int dx = 2;
        private int dy = 2;
        private int delay = 10;
        private static final int RADIUS = 30;

       
        public Color getWarna()
        {
         r=new Random();
         return color=new Color((int)r.nextInt(255),(int)r.nextInt(256),(int)r.nextInt(255));
        }


        public void draw(Graphics g)
        {
            g.setColor(color);
            if(bulat==true)
                g.fillOval(x, y, RADIUS, RADIUS);
            else
                g.fillRect(x, y, RADIUS, RADIUS);
        }

        /**
         * Updates the position of the bola, taking care of bounces.
         */
        public void move()
        {
            x += dx;
            y += dy;
            if (x < 0)
            {
                // Bounce off left wall.
                x = 0; dx = -dx;
                getWarna();
                            }
            if (x + RADIUS >= tempat.getWidth())
            {
                // Bounce off right wall.
                x = tempat.getWidth() - RADIUS; dx = -dx;
                getWarna();
            }
            if (y < 0)
            {
                // Bounce off top wall.
                y = 0; dy = -dy;
                getWarna();
            }
            if (y + RADIUS >= tempat.getHeight())
            {
                // Bounce off bottom wall.
                y = tempat.getHeight() - RADIUS; dy = -dy;
                getWarna();
           }
        }

        public void run()
        {
            for (int i = 1; i <= 99999; i++)
            {
                move();
                try {Thread.sleep(delay);} catch(InterruptedException e)
                {
                }
            }
            listBola.remove(this);
        }

    }

    public static void main(String[] args)
    {
        bolapantul ujiBola1 = new bolapantul();
        ujiBola1.setTitle("Bola Pantul Sederhana");
        ujiBola1.setLocation(450,150);
        ujiBola1.setSize(550, 450);
        ujiBola1.show();
        ujiBola1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        ujiBola1.thread1.setPriority(Thread.MAX_PRIORITY);
        ujiBola1.thread1.start();
    }
}