BouncingBall

package javafx;


import javax.swing.*;
import java.awt.*;
import java.awt.event.*;


/**
 *
 * @author Compsci
 */
public class BouncingBall extends JApplet{

    private final int X = 200;
    private final int WIDTH = 40;
    private final int HEIGHT = 40;
    private final int TIME_DELAY = 30;
    private final int MOVE = 20;
    private final int MINIMUM_Y = 50;
    private final int MAXIMUM_Y = 400;
    private int y = 400;
    private Timer timer;
    private boolean goingUp = true;

    public void init() {
        timer = new Timer(TIME_DELAY, new TimerListener());
        timer.start();

    }

    public void paint(Graphics g) {
        super.paint(g);
        g.setColor(Color.RED);
        g.fillOval(X, y, WIDTH, HEIGHT);
    }

    private class TimerListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            if (goingUp){
                if (y > MINIMUM_Y)
                    y -= MOVE;
                else
                    goingUp = false;
            }
            else{
                if (y < MAXIMUM_Y)
                    y += MOVE;
                else
                    goingUp = true;
            }

            repaint();
        }
    }
}