How do I access objects from the original Thread?

Question

I have this simple JApplet that just makes a circle bounce around the screen. Here it is:
import java.awt.Color;
import javax.swing.JApplet;
import java.awt.Graphics;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;
public class TestApplet3 extends JApplet implements MouseListener {
    private int lastX;          // x coordinate of circle
    private int lastY;          // y coordinate of circle
    private int d = 15;          // diameter of circle
    public void paint(Graphics g) {
    public void init() {
        addMouseListener(this);
    public void mouseClicked(MouseEvent event) {
        Graphics gx = this.getGraphics();
        for (int x = 0, y = 0, count = 0, horiz = 2, vert = 2, k = 2; count < 1000; x = x + horiz, y = y + vert, count++) {
            if ((x + d) >= 350) {
                horiz = -horiz;
            if ((x <= 0) && (horiz < 0)) {
                horiz = -horiz;
            if ((y + d) >= 200) {
                vert = -vert;
            if ((y <= 0) && (vert < 0)) {
                vert = -vert;
            gx.setColor(Color.WHITE);
            gx.fillOval(lastX, lastY, d, d);
            gx.setColor(Color.RED);
            lastX = x;
            lastY = y;
            gx.fillOval(lastX, lastY, d, d);
            try {
                Thread.sleep(20);
            } catch (Exception ex) {
                System.out.println(ex.getMessage());
    public void mouseEntered(MouseEvent event) {
    public void mouseExited(MouseEvent event) {
    public void mousePressed(MouseEvent event) {
    public void mouseReleased(MouseEvent event) {
}But now I'd like to change it so that when the mouse is clicked a new Thread is spawned to run the code within the mouseClicked method..... this will allow multiple circles to bounce around and will also keep the applet responsive to new mouse clicks... so I've tried changing it below:
* To change this template, choose Tools | Templates
* and open the template in the editor.
package runninggraph;
* @author epuknol
import java.awt.Color;
import javax.swing.JApplet;
import java.awt.Graphics;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;
public class TestApplet3 extends JApplet implements MouseListener, Runnable {
    private int lastX;          // x coordinate of circle
    private int lastY;          // y coordinate of circle
    private int d = 15;          // diameter of circle
    public void paint(Graphics g) {
    public void init() {
        addMouseListener(this);
    public void run() {
        Graphics gx = this.getGraphics();
        for (int x = 0, y = 0, count = 0, horiz = 2, vert = 2, k = 2; count < 1000; x = x + horiz, y = y + vert, count++) {
            if ((x + d) >= 350) {
                horiz = -horiz;
            if ((x <= 0) && (horiz < 0)) {
                horiz = -horiz;
            if ((y + d) >= 200) {
                vert = -vert;
            if ((y <= 0) && (vert < 0)) {
                vert = -vert;
            gx.setColor(Color.WHITE);
            gx.fillOval(lastX, lastY, d, d);
            gx.setColor(Color.RED);
            lastX = x;
            lastY = y;
            gx.fillOval(lastX, lastY, d, d);
            try {
                Thread.sleep(20);
            } catch (Exception ex) {
                System.out.println(ex.getMessage());
    public void mouseClicked(MouseEvent event) {
        (new Thread(new TestApplet())).start();       
    public void mouseEntered(MouseEvent event) {
    public void mouseExited(MouseEvent event) {
    public void mousePressed(MouseEvent event) {
    public void mouseReleased(MouseEvent event) {
}but this doesn't work - I think because the this.getGraphics() doesn't refer back to the same object ..... I've tried some other things too - like defining the Graphics gx as a class variable and initializing it before spawning the new Thread ... but I can't access gx using that technique either.
Can somebody please help me get where I'm trying to go?
Thanks.

Answer 1

Aw heck, got bored. For instance, this draws a bunch of balls without a direct call to Thread anything:
BouncingCircles.java
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JPanel;
import javax.swing.Timer;
* creates a JPanel that draws bouncing circles within it. 
* @author Pete
public class BouncingCircles {
  private static final int DELAY = 15;
  private static final int DIAMETER = 15;
  private static final int DELTA = 5;
  List<Ball> ballList = new ArrayList<Ball>(); // list of all balls
  private JPanel mainPanel = new JPanel() {
    @Override
    protected void paintComponent(Graphics g) {
      super.paintComponent(g);
      myPaint(g);
  // Swing Timer that tells the balls to move and tells the JPanel to then draw them
  private Timer sTimer = new Timer(DELAY, new ActionListener() {
    public void actionPerformed(ActionEvent e) {
      timerAction(e);
  public BouncingCircles() {
    mainPanel.setPreferredSize(new Dimension(400, 400));
    mainPanel.addMouseListener(new MouseAdapter() {
      @Override
      // add new ball with each mouse press
      public void mousePressed(MouseEvent e) {
        ballList.add(new Ball(e.getPoint(), new Point(DELTA, DELTA)));
    sTimer.start();
  public JPanel getPanel() {
    return mainPanel;
  private void timerAction(ActionEvent e) {
    Dimension d = mainPanel.getSize();
    for (Ball ball : ballList) {
      if (ball.getPoint().x < 0) {
        ball.setXDirectionRight(true);
      } else if (ball.getPoint().x + DIAMETER > d.width) {
        ball.setXDirectionRight(false);
      if (ball.getPoint().y < 0) {
        ball.setYDirectionDown(true);
      } else if (ball.getPoint().y + DIAMETER > d.height) {
        ball.setYDirectionDown(false);
      ball.increment();
    mainPanel.repaint();
   * paintComponent method draws all balls in List
   * @param g
  private void myPaint(Graphics g) {
    g.setColor(Color.red);
    Graphics2D g2d = (Graphics2D) g;
    RenderingHints rh = new RenderingHints(RenderingHints.KEY_ANTIALIASING,
        RenderingHints.VALUE_ANTIALIAS_ON);
    g2d.setRenderingHints(rh);
    for (Ball ball : ballList) {
      g.fillOval(ball.getPoint().x, ball.getPoint().y, DIAMETER, DIAMETER);
  private class Ball {
    private Point point = new Point();
    private Point velocity = new Point();
    public Ball(Point point, Point velocity) {
      this.point = point;
      this.velocity = velocity;
    public Point getPoint() {
      return point;
    public Point getVelocity() {
      return velocity;
    public void increment() {
      point = new Point(point.x + velocity.x, point.y + velocity.y);
    public void setXDirectionRight(boolean right) {
      int newVelocityX = Math.abs(velocity.x);
      if (!right) {
        newVelocityX = -newVelocityX;
      velocity = new Point(newVelocityX, velocity.y);
    public void setYDirectionDown(boolean down) {
      int newVelocityY = Math.abs(velocity.y);
      if (!down) {
        newVelocityY = -newVelocityY;
      velocity = new Point(velocity.x, newVelocityY);
}And this displays the JPanel produced above in a standard JApplet.
BouncingCircApplet.java
import java.lang.reflect.InvocationTargetException;
import javax.swing.JApplet;
import javax.swing.SwingUtilities;
public class BouncingCircApplet extends JApplet {
  @Override
  public void init() {
    try {
      SwingUtilities.invokeAndWait(new Runnable() {
        public void run() {
          getContentPane().add(new BouncingCircles().getPanel());
    } catch (InterruptedException e) {
      e.printStackTrace();
    } catch (InvocationTargetException e) {
      e.printStackTrace();
}