/*****************************************
 * An abstract class that handles the specifics
 * of animation.  All the user has to do is 
 * implement subclass specific behavior.
*****************************************/ 

public abstract class AnimationApplet extends java.applet.Applet implements Runnable{
    // the thread that does the redrawing
    private Thread animationThread = null; 
    // how often the thread redraws itself
    private int delay; 
    
    public void start(){
        if (animationThread == null){
            animationThread = new Thread(this); 
            animationThread.start(); 
        }
    }
    
    public void stop(){ 
        animationThread = null; 
    } 
    
    public void run(){ 
        while (Thread.currentThread() == animationThread){ 
            repaint(); 
            try{ 
                Thread.currentThread().sleep(delay); 
            } 
            catch(InterruptedException e){/* don't do anything*/} 
        } 
    }
    
    // Java bean pattern to enforce encapsulation
    public void setDelay(int delay){
        this.delay = delay;
    }
    // Java bean pattern to enforce encapsulation
    public int getDelay(){
        return delay;
    }
}