import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;

public class Ball extends Applet
                            implements Runnable {
    int frameNumber = -1;
    int delay;
    Thread animatorThread;

    public void init() {
        String str;
        int fps = 10;

        //How many milliseconds between frames?
        str = getParameter("fps");
        try {
            if (str != null) {
                fps = Integer.parseInt(str);
            }
        } catch (Exception e) {}
        delay = (fps > 0) ? (1000 / fps) : 100;
    }

    public void start() {
            //Start animating!
            if (animatorThread == null) {
                animatorThread = new Thread(this);
            }
            animatorThread.start();
    }

    public void stop() {
        //Stop the animating thread.
        animatorThread = null;

        animatorThread = null;
    }

    public void run() {
        //Just to be nice, lower this thread's priority
        //so it can't interfere with other processing going on.
        Thread.currentThread().setPriority(Thread.MIN_PRIORITY);

        //Remember which thread we are.
        Thread currentThread = Thread.currentThread();

        //This is the animation loop.
        while (currentThread == animatorThread) {
            //Advance the animation frame.
            frameNumber++;

            //Display it.
            repaint();

            // Delay
            try {
                Thread.sleep(delay);
            } catch (InterruptedException e) {
                break;
            }
        }
    }

    public void paint(Graphics g) {
        setBackground(Color.white);
        g.setColor(Color.red);
        Dimension d = getSize();
        if (frameNumber % 2 == 1)
           g.fillOval(0, 0, d.width/2, d.height/2);
        else g.fillOval(0, d.height/2, d.width/2, d.height/2);
    }
}