Source of BouncingBall2.java

Structures and functions

public class BouncingBall2 extends DBAnimationApplet 

  1: import java.awt.*;
  2: 
  3: public class BouncingBall2 extends DBAnimationApplet {
  4: 
  5:   public BouncingBall2() {
  6:     super(true);  // double buffering
  7:   }
  8: 
  9:   protected void initAnimator() {
 10:     String att = getParameter("delay");
 11:     if (att != null)
 12:       setDelay(Integer.parseInt(att));
 13:     x = d.width * 2 / 3 ;
 14:     y = d.height - radius;
 15:   }
 16: 
 17: 
 18:   protected void paintFrame(Graphics g) {
 19:     g.setColor(Color.white);
 20:     g.fillRect(0,0,d.width,d.height);
 21:     if (x < radius || x > d.width - radius) {
 22:       dx = -dx;
 23:     }
 24: 
 25:     if (y < radius || y > d.height - radius) {
 26:       dy  =  -dy;
 27:     }
 28:     x += dx; y += dy;
 29:     g.setColor(color);
 30:     g.fillOval(x - radius, y - radius, radius * 2, radius * 2);
 31:   }
 32: 
 33:   protected int x, y;
 34:   protected int dx = -2, dy = -4;
 35:   protected int radius = 20;
 36:   protected Color color = Color.green;
 37: }