New to Java. Need some proformance suggestions

[Lamar Jared]

I am new to java. I am teaching myself the language. I have this bouncing ball program. When the start button is pressed the ball drops and bounces around the panel. Each time you press start a new ball is created. The problem is each new ball slows down the program. Is there a way to correct this?

Sorry if this isn't the correct place for this topic.

 
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;
 
import javax.swing.JPanel;
 
class Ball extends Thread {
 
private JPanel box;
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 Ball(JPanel b) {
box = b;
}
 
public void draw() {
Graphics g = box.getGraphics();
Graphics2D g2 = (Graphics2D) g;
g2.fill(new Ellipse2D.Double(x, y, XSIZE, YSIZE));
g2.dispose();
}
 
public void move() {
 
Graphics g = box.getGraphics();
Graphics2D g2 = (Graphics2D) g;
g2.setXORMode(box.getBackground());
g2.fill(new Ellipse2D.Double(x, y, XSIZE, YSIZE));
x += dx;
y += dy;
if (x < 0) {
x = 0;
dx = -dx;
}
if (x + XSIZE >= box.getWidth()) {
x = box.getWidth() - XSIZE;
dx = -dx;
}
if (y < 0) {
y = 0;
dy = -dy;
}
if (y + YSIZE >= box.getHeight()) {
y = box.getHeight() - YSIZE;
dy = -dy;
}

g2.fill(new Ellipse2D.Double(x, y, XSIZE, YSIZE));
g2.dispose();
 
//box.paint(box.getGraphics());
 
}
 
public void run() {
try {
draw();
for (int i = 1; i <= 1000; i++) {
move();
sleep(1);
}
} catch (InterruptedException e) {
// TODO: handle exception
}
}
 
}   

import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
 
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
 
public class Bouncing extends JFrame {
 
private JPanel canvas;
 
public Bouncing() {
setSize(500, 500);
setTitle("Bouncy Ball");
 
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
 
Container con = getContentPane();
canvas = new JPanel();
con.add(canvas, "Center");
JPanel p = new JPanel();
addButton(p, "Start", new ActionListener() {
public void actionPerformed(ActionEvent evt) {
Ball b = new Ball(canvas);
b.start();
}
});
 
addButton(p, "Close", new ActionListener() {
public void actionPerformed(ActionEvent evt) {
canvas.setVisible(false);
System.exit(0);
}
});
con.add(p, "South");
}
 
public void addButton(Container c, String title, ActionListener a) {
JButton b = new JButton(title);
c.add(b);
b.addActionListener(a);
}
 
public static void main(String[] args) {
JFrame f = new Bouncing();
f.setVisible(true);
}
}

[ December 22, 2008: Message edited by: Lamr Jared ]

[Campbell Ritchie]

Welcome to JavaRanch

How are you scheduling re-drawing the Balls? You are using Thread.sleep(). I think Thread.sleep(1) is a bit short; it can take more than 1 millisecond to repaint the entire GUI. Try giving a longer delay, maybe 20.

There have been problems on Windows with timings which don't divide exactly by 10. I can't remember the details, but it can cause the system clock to show incorrect times.

That sort of question is more difficult than the average beginner's question; it might be appropriate for the Swing forum or the Performance forum, but I think you might get more attention in Swing . . . moving.

[Steve Luke]

So I think you have several problems with this, but the biggest is that you have every ball have its own thread.The more balls you have (quiet down kiddies ) the more threads, and the more work it is to schedule between the threads.

The better bet would be to have just a few background threads, 1 to schedule the moving and another 1 to schedule repainting. Both should be scheduled at a fixed rate, rather than using Thread.sleep, which would be a fixed delay. Take a look at Timer and TimerTask, or ScheduledExecutorService to do this.

The Ball itself would be a normal object which keeps track of its position and can handle painting itself.

[Michael Dunn]

> So I think you have several problems with this,...

there are major problems with the whole lot:
- indiscremenent use of the swing thread
- getGraphics() (which is a wrist-slasher)

the only hope is ctrl-a-delete and start again.

to start again, start here:

http://java.sun.com/docs/books/tutorial/uiswing/painting/index.html

[Rob Spoor]

Lamr, please Use A Meaningful Subject Line. "Java Help" doesn't quite describe the problem accurately; about 99% of all threads are about Java help.

You can use the edit button to change it.

[Lamar Jared]

I appreciate all the help. I am only 6 months in working with Java. I don't know all the strengths yet. Thanks again everyone.
[ December 22, 2008: Message edited by: Lamar Jared ]