// JDK 1.1.1

import java.awt.*;

public class BouncingBallCanvas extends Canvas {
  int x, y, dx = -4, dy = -8, radius = 20; 
  Dimension d;
  Image im;
  Graphics offscreen;
  Color ballcolor = Color.red; 

  public void init() {
    d = getSize();
    x = d.width * 2 / 3 ;
    y = d.height - radius;
  }
  
  public void update(Graphics g) {
    if (im == null) {
      im = createImage(d.width, d.height);
      offscreen = im.getGraphics();
    }
    offscreen.setColor(Color.white);
    offscreen.fillRect(0,0,d.width,d.height); 
    if (x < radius || x > d.width - radius) {
      dx = -dx; 
    }
    if (y < radius || y > d.height - radius) {
      dy = -dy; 
    }
    x += dx; y += dy; 
    offscreen.setColor(ballcolor);
    offscreen.fillOval(x - radius, y - radius, radius * 2, radius * 2);
    g.drawImage(im, 0, 0, this);
  }  
  public void paint(Graphics g) {
    update(g); 
  }

  public void setColor(Color c) {
    ballcolor = c; 
  }
}