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

/* From Textbook */ 

public class BounceThread {
    public static void main(String[] args) {
	EventQueue.invokeLater(new Runnable() {
		public void run() {
		    JFrame frame = new BounceFrame();
		    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		    frame.setVisible(true);
		}
	    });
    }
}

class Ball {
    public void move(Rectangle2D bounds) {
	x += dx; 
	y += dy; 

	if(x < bounds.getMinX()) {
	    x = bounds.getMinX(); 
	    dx = -dx;
	}
	if(x + XSIZE >= bounds.getMaxX()){
	    x = bounds.getMaxX() - XSIZE;
	    dx = -dx;
	}

	if(y < bounds.getMinY()) {
	    y = bounds.getMinY(); 
	    dy = -dy;
	}
	if(y + YSIZE >= bounds.getMaxY()){
	    y = bounds.getMaxY() - YSIZE;
	    dy = -dy;
	}
    }

    public Ellipse2D getShape() {
	return new Ellipse2D.Double(x,y,XSIZE,YSIZE);
    }

    private static final int XSIZE = 15; 
    private static final int YSIZE = 15; 
    private double x = 0; 
    private double y = 0; 
    private double dx = 1; 
    private double dy = 1; 
}

class BallRunnable implements Runnable {
    public BallRunnable(Ball aBall, Component aComponent) {
	ball = aBall;
	component = aComponent;
    }

    public void run() {
	try {
	    for(int i = 1; i < STEPS; i++) {
		ball.move(component.getBounds());
		component.repaint(); 
		Thread.sleep(DELAY);
	    }
	}
	catch(InterruptedException exp) {
	}
    }

    private Ball ball;
    private Component component;
    public static final int STEPS = 1000; 
    public static final int DELAY = 5; 
}

class BounceFrame extends JFrame {
    public BounceFrame() {
	setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
	setTitle("Bounce Thread");

	comp = new BallComponent(); 
	add(comp, BorderLayout.CENTER);
	JPanel buttonPanel = new JPanel();
	addButton(buttonPanel, "Start", new ActionListener() {
		public void actionPerformed(ActionEvent evt) { addBall(); }
	    });
	
	addButton(buttonPanel, "Close", new ActionListener() {
		public void actionPerformed(ActionEvent evt) { System.exit(0); }
	    });

	add(buttonPanel, BorderLayout.SOUTH);
    }

    public void addButton(Container c, String title, ActionListener listener) {
	JButton button = new JButton(title); 
	c.add(button);
	button.addActionListener(listener);
    }

    public void addBall() {
	Ball b = new Ball(); 
	comp.addBall(b); 
	Runnable r = new BallRunnable(b, comp); 
	Thread t = new Thread(r); 
	t.start();
    }

    private BallComponent comp; 
    public static final int DEFAULT_WIDTH = 450;
    public static final int DEFAULT_HEIGHT = 350;
    public static final int STEPS = 2000; 
    public static final int DELAY = 3; 
}



class BallComponent extends JPanel {
    public void addBall(Ball b) {
	balls.add(b);
    }

    public void paintComponent(Graphics g) {
	super.paintComponent(g);   // erase background
	Graphics2D g2 = (Graphics2D) g;
	for(Ball b : balls)
	    g2.fill(b.getShape());
    }

    private ArrayList<Ball> balls = new ArrayList<Ball>();
}