Looks like a bug in Java ... what's going on he

Question

I can't really recreate this problem, but it occurs in situations like the one below. Unfortunately the program is just too complex to post it all here. In other words, I'm not sure if this exact code will produce the bug, but it happens sometimes in similar situations:
        System.out.println("arrived here");
        // while not ready
        System.out.print("waiting until initialisation is ready..."+AnimationFrameManager.printCurrentFrame()+" ... ");
        // System.out.println("THIS LINE HAS BEEN PRINTED");
       while (!this.isReady)
            // do nothing
        System.out.println("done!");The bug is that I get output like this:-
arrived here
waiting until initialisation is ready...3...waiting until initialisation is ready...3...done!Why is it printing twice?
Weirder still is that if I put a line in-between the last println statement and the beginning of the while loop (for example, the line that is commented out above), then it works as expected!
i.e.
arrived here
THIS LINE HAS BEEN PRINTED
waiting until initialisation is ready...3...done!If I take the static method call out, it works as expected:
        System.out.println("arrived here");
        // while not ready
        System.out.print("waiting until initialisation is ready... "); // <!-- took the static method call out
        // System.out.println("THIS LINE HAS BEEN PRINTED");
       while (!this.isReady)
            // do nothing
        System.out.println("done!");Any ideas?
Edited by: GallahJava on Feb 2, 2010 7:47 PM
Edited by: GallahJava on Feb 2, 2010 7:52 PM

Answer 1

There is no GUI, just console output.
I realise there is multi-threading going on "behind the scenes", but I haven't explicitly created any threads except for one; this is the one-and-only thread created by me, does this help? I can't imagine how it could possibly be responsible for these "multithreading issues".
public class AnimationRunner implements Runnable
    private SuperImage[] images;
    private int imageNo;
    private static final int MAX_IMAGES = 39; // How many images in the progression?
    private static final int SWAP_DELAY = 850;
    public AnimationRunner()
            images = new SuperImage[MAX_IMAGES];
            System.out.print("\nInitialising images to memory...");
            for (int x = 0; x < MAX_IMAGES; x++)
                String imageFile = "images/anim-frame-" + (x + 1) + ".png";
                //System.out.println(imageFile);
                images[x] = SuperImage.createFrom(imageFile);
            System.out.println("done!");
            imageNo = 0;
            new Thread(this).start();
    public void run()
        System.out.println("Animation has started.");
        while (true)
            try
                Thread.sleep(SWAP_DELAY);
                if (imageNo >= MAX_IMAGES - 1)
                    imageNo = 1;
                else
                    imageNo++;
                //System.out.println("Now on image #" + (imageNo + 1) + "\n");
            catch (Exception e)
    public int getImageNo()
        return imageNo + 1;
    public SuperImage getImage()
        //System.out.println("\n(using image no."+(imageNo+1)+")\n");
        return images[imageNo];
}