Bouncing Ball Just Suddenly Stops Mid Bounce

Question

I have a application where each time you click the add ball button a new randomly colored ball is added to the jpanel. It works fine except that the balls suddenly stop at the same spot. I want them to continue to bounce for a longer period of time instead of like 8 bounces. It was going around withoutstopping prior to my getting the add new ball part working. I cannot seem to figure out what I did wrong. Also curious if anyone new of a tip as to how to get the balls to disappear once a button is clicked or their cycle runs out. Below is my code:
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.*;
import javax.swing.*;
public class BounceBall{
    public static void main(String[] args) {
        JFrame frame = new BounceFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOS  E);
        frame.setVisible(true);
class BounceFrame extends JFrame {
    private BallCanvas canvas;
    public static final int WIDTH = 450;
    public static final int HEIGHT = 350;
    public BounceFrame() {
        setSize(WIDTH, HEIGHT);
        setTitle("BounceThread");
        Container contentPane = getContentPane();
        canvas = new BallCanvas();
        contentPane.add(canvas, BorderLayout.CENTER);
        JPanel buttonPanel = new JPanel();
        addButton(buttonPanel, "Add Ball",
                new ActionListener() {
            public void actionPerformed(ActionEvent evt) {
                addBall();
        addButton(buttonPanel, "Exit",
                new ActionListener() {
            public void actionPerformed(ActionEvent evt) {
                System.exit(0);
class BallThread extends Thread {
    private BouncingBall b;
    public BallThread(BouncingBall aBall) { b = aBall; }
    public void run() {
        try {
            for (int i = 1; i <= 1000; i++) {
                b.move();
                sleep(5);
        } catch (InterruptedException exception) {
class BallCanvas extends JPanel {
    private ArrayList balls = new ArrayList();
    public void add(BouncingBall b) {
        balls.add(b);
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        for (int i = 0; i < balls.size(); i++) {
            BouncingBall b = (BouncingBall)balls.get(i);
            b.draw(g2);
class BouncingBall {
    private Component canvas;
    private static final int XSIZE = 15;
    private static final int YSIZE = 15;
    private int x = 0;
    private int y = 0;
    private int dx = 2;
    private int dy = 2;
    public BouncingBall(Component c) { canvas = c; }
    Color color = getColor();
    public void draw(Graphics2D g2) {
        g2.setColor(color);
        g2.fillOval(x,y,30,30);   // adds color to circle
        g2.drawOval(x,y,30,30);   // draws circle
    public void move() {
        x += dx;
        y += dy;
        if (x < 0) {
            x = 0;
            dx = -dx;
        if (x + XSIZE >= canvas.getWidth()) {
            x = canvas.getWidth() - XSIZE;
            dx = -dx;
        if (y < 0) {
            y = 0;
            dy = -dy;
        if (y + YSIZE >= canvas.getHeight()) {
            y = canvas.getHeight() - YSIZE;
            dy = -dy;
        canvas.repaint();
    private Color getColor() {
        int rval = (int)Math.floor(Math.random() * 256);
        int gval = (int)Math.floor(Math.random() * 256);
        int bval = (int)Math.floor(Math.random() * 256);
        return new Color(rval, gval, bval);
    }Edited by: wnymetsfan on Dec 2, 2007 2:01 PM

Answer 1

wnymetsfan wrote:
Actually it is comiliable as I ran it numerous times today asI tried to fix it. No, it does not compile. Besides the obvious error:
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOS  E);, a large part of the BounceFrame class seems to be missing: I don't see a addButton(...) anywhere.
I posted here since it says new to java which I am. I also have posted here before with questions relatedto swing and 2D elements like graphs and no one else had an issue. It's not prohibited to post it here, but in the 2d forums, there are more people who know what they're talking about when it comes to 2D animations.
Thanks for the links to the other forums I will post there. Sorry to bother you guys as I was not aware that New to Java meant only if it doesn't involves things like swing and 2DIt's not a bother: I merely said it for you to get help sooner.