Trouble wih threads

[jammas615]

Hi,

I have one single thread that i wish to start but whatever i try, i can't make it work. I start the thread in the main Class' constructor and call the constructor from main().

Here's a very cut down version:

public class TwoDWorld extends JPanel implements KeyListener, Runnable{

    Thread t;
    long startingTime = 0;
    long passedTime = 0;

    public TwoDWorld() {
        t = new Thread();   
        t.start();
        }

	public static void main(String args[]) {
		new TwoDWorld();
	}

	public void run() {
		long startingTime = System.currentTimeMillis();
		long totalTime = startingTime;
		System.out.println("hey");
		while (true) {
			try {
				passedTime = System.currentTimeMillis() - totalTime;
				totalTime += passedTime;
				
				update();
				draw();				
				render();
				t.sleep(50);
				
			} catch (Exception e) {}
		}
		
	}

My thread is not starting for some reason because "hey" is not shown in the command line.
Any thoughts?

Thanks, James.

[Norm]

What connects the Thread object you "start" with any code to be executed?

[doWhile]

You have to pass your Runnable to the Thread object so that object knows what Runnable interface to run, otherwise it will run its default.

[jammas615]

But doesn't implementing runnable start the run(); method when start(); is called?

[Norm]

Yes, the start method causes the Thread class's run method to be executed.
Where do you tell the Thread class about your run() method?

Read the API doc for the Thread class's run method.

[jammas615]

I now start the thread like this:

Thread t;

public TwoDWorld() {        
        TwoDWorld tdw = new TwoDWorld();
        t = new Thread(tdw);
        t.start();
}

The thread starts fine but something is causing windows to rapidly open.
Why? Im lost

[Norm]

EDIT:
Sorry I am answering questions on another thread about this same topic and have confused my answers.

something is causing windows to rapidly open.

Can you explain what happens?

[jammas615]

Throws:
IllegalThreadStateException - if the thread was already started.

It just runs until i get memory errors.

[Norm]

See my last post. I was on another similiar topic and got them confused.

something is causing windows to rapidly open.

Can you explain what happens?

[jammas615]

When i run the program, a black window opens, and across the windows taskbar, a whole line of the same process opens and just keeps opening rapidly. I then start to get errors like this:

Exception in thread "AWT-EventQueue-0" java.lang.OutOfMemoryError: Java heap space
	at java.awt.image.DataBufferInt.<init>(Unknown Source)
	at java.awt.image.Raster.createPackedRaster(Unknown Source)
	at java.awt.image.DirectColorModel.createCompatibleWritableRaster(Unknown Source)
	at java.awt.GraphicsConfiguration.createCompatibleImage(Unknown Source)
	at java.awt.GraphicsConfiguration.createCompatibleImage(Unknown Source)
	at sun.awt.image.SunVolatileImage.getBackupImage(Unknown Source)
	at sun.awt.image.VolatileSurfaceManager.getBackupSurface(Unknown Source)
	at sun.awt.image.VolatileSurfaceManager.initialize(Unknown Source)
	at sun.awt.image.SunVolatileImage.<init>(Unknown Source)
	at sun.awt.image.SunVolatileImage.<init>(Unknown Source)
	at sun.awt.image.SunVolatileImage.<init>(Unknown Source)
	at sun.awt.image.SunVolatileImage.<init>(Unknown Source)
	at sun.awt.windows.WComponentPeer.createVolatileImage(Unknown Source)
	at java.awt.Component.createVolatileImage(Unknown Source)
	at java.awt.Component$BltBufferStrategy.createBackBuffers(Unknown Source)
	at java.awt.Component$BltBufferStrategy.<init>(Unknown Source)
	at java.awt.Component$BltSubRegionBufferStrategy.<init>(Unknown Source)
	at java.awt.Component.createBufferStrategy(Unknown Source)
	at java.awt.Window.createBufferStrategy(Unknown Source)
	at javax.swing.BufferStrategyPaintManager$BufferInfo.createBufferStrategy(Unknown Source)
	at javax.swing.BufferStrategyPaintManager$BufferInfo.createBufferStrategy(Unknown Source)
	at javax.swing.BufferStrategyPaintManager$BufferInfo.getBufferStrategy(Unknown Source)
	at javax.swing.BufferStrategyPaintManager.prepare(Unknown Source)
	at javax.swing.BufferStrategyPaintManager.paint(Unknown Source)
	at javax.swing.RepaintManager.paint(Unknown Source)
	at javax.swing.JComponent.paint(Unknown Source)
	at java.awt.GraphicsCallback$PaintCallback.run(Unknown Source)
	at sun.awt.SunGraphicsCallback.runOneComponent(Unknown Source)
	at sun.awt.SunGraphicsCallback.runComponents(Unknown Source)
	at java.awt.Container.paint(Unknown Source)
	at java.awt.Window.paint(Unknown Source)
	at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)

[Norm]

I don't see any references to your program's classes in the stack trace.
Try adding lots of printlns to your code to show the execution flow to find the location where the error is occuring.

[jammas615]

This line:

TwoDWorld tdw = new TwoDWorld();

Was causing it.
I changed it to this:

t = new Thread(this);
t.start();

[Norm]

You had a recursive loop: the constructor was calling the constructor over and over.
Did you leave off some of the stack trace that showed that?