OutOfMemory... leak somewhere in this class

Question

I've been programming Java for a few months, and have for the past few weeks been working on this Swing GUI RPG. I know that the below code could be optimised a certain amount by doing lots of things I don't understand but for now all I'm looking for is a memory leak which is causing this to crash after a few minutes of wandering the map.
class GamePanel extends JPanel implements Runnable, KeyListener
    MediaTracker gameStartTracker = new MediaTracker (this);
    MediaTracker gameRunTracker = new MediaTracker (this);
    Toolkit toolkit = Toolkit.getDefaultToolkit ();
    Image worldMap;
    Image mapOnScreen;
    Image worldMapMask;
    int pixels [];
    Player PC = Global.PC;
    Thread GameThread;
    Timer runTimer;
    boolean hasMoved = true; // Cuts out some of the processor usage.
    public GamePanel ()
     PC.reset(0);
        addKeyListener (this);
     GameThread = new Thread (this);
     // Loads GIF's
     try
            worldMap = toolkit.getImage (getClass().getResource("wmap.gif"));
            worldMapMask = toolkit.getImage (getClass().getResource("wmask.gif"));
        catch(Exception ex)
            System.err.println("Could not load world map or it's mask");
     gameStartTracker.addImage (worldMap, 0);
     gameStartTracker.addImage (worldMapMask, 1);
     try
         gameStartTracker.waitForAll();
     catch (InterruptedException ex)
         System.out.println ("Can not process Game Image");
     // Grabs all of the the pixels from the mask
     pixels = new int [worldMapMask.getWidth (this) * worldMapMask.getHeight (this)];
     PixelGrabber pg = new PixelGrabber (worldMapMask, 0, 0, worldMapMask.getWidth (this), worldMapMask.getHeight (this), pixels, 0, worldMapMask.getWidth (this));
     try
         pg.grabPixels ();
     catch (InterruptedException ex)
         System.out.println ("Internal difficulty");
        worldMap.flush();
        worldMapMask.flush();
     runWork ();
    public boolean isFocusTraversable ()
     return true;
    public void paintComponent(Graphics g)
        super.paintComponent(g);
     g.drawImage (mapOnScreen, 1, 1, this);
     g.drawImage (PC.mapIcon, 320, 240, this);
        mapOnScreen.flush();
    public void runWork ()
     if (hasMoved)
         mapOnScreen = createImage (new FilteredImageSource (worldMap.getSource (), new CropImageFilter (PC.x - 320, PC.y - 240, 639, 479)));
            try
                PC.mapIcon = toolkit.getImage (getClass().getResource(PC.mapPicURL));
            catch(Exception ex)
                System.err.println("Could not load character icon!");
         gameRunTracker.addImage (mapOnScreen, 0);
         gameRunTracker.addImage (PC.mapIcon, 1);
         try
          gameRunTracker.waitForAll ();
         catch (InterruptedException ex)
          System.err.println ("Can not process image");
            repaint();
         hasMoved = false;
    public void run ()
     while (true)
         runWork ();
    public void startGame ()
     hasMoved = true;
     GameThread.start();
    public void keyPressed (java.awt.event.KeyEvent keyEvent)
     hasMoved = true;
     if (keyEvent.getKeyCode () == KeyEvent.VK_RIGHT)
         int pixel = pixels [PC.y * worldMapMask.getWidth (this) + (PC.x + PC.mapIcon.getWidth (this) + PC.speed)];
         int red = (pixel >> 16) & 0xff;
         int green = (pixel >> 8) & 0xff;
         int blue = (pixel) & 0xff;
         if (red != 0 && green != 0 && blue != 0)
          PC.mapPicURL = "pcr0.gif";
          PC.x = PC.x + PC.speed;
     else if (keyEvent.getKeyCode () == KeyEvent.VK_LEFT)
         int pixel = pixels [PC.y * worldMapMask.getWidth (this) + (PC.x - PC.speed)];
         int red = (pixel >> 16) & 0xff;
         int green = (pixel >> 8) & 0xff;
         int blue = (pixel) & 0xff;
         if (red != 0 && green != 0 && blue != 0)
          PC.mapPicURL = "pcl2.gif";
          PC.x = PC.x - PC.speed;
     else if (keyEvent.getKeyCode () == KeyEvent.VK_DOWN)
         int pixel = pixels [(PC.y + PC.mapIcon.getHeight (this) + PC.speed) * worldMapMask.getWidth (this) + PC.x];
         int red = (pixel >> 16) & 0xff;
         int green = (pixel >> 8) & 0xff;
         int blue = (pixel) & 0xff;
         if (red != 0 && green != 0 && blue != 0)
          PC.mapPicURL = "pcd0.gif";
          PC.y = PC.y + PC.speed;
     else if (keyEvent.getKeyCode () == KeyEvent.VK_UP)
         int pixel = pixels [(PC.y - PC.speed) * worldMapMask.getWidth (this) + PC.x];
         int red = (pixel >> 16) & 0xff;
         int green = (pixel >> 8) & 0xff;
         int blue = (pixel) & 0xff;
         if (red != 0 && green != 0 && blue != 0)
          PC.mapPicURL = "pcu0.gif";
          PC.y = PC.y - PC.speed;
     else
    public void keyReleased (java.awt.event.KeyEvent keyEvent)
    public void keyTyped (java.awt.event.KeyEvent keyEvent)

Answer 1

Hello,
I am not sure if this will fix your problem but here goes,
First off run your application through a profiler it may well give you some clues as to where the problem lies.
Have you tried increasing the heap memory allocated to your JVM, it may be that you just need more memory than you exapectd
e.g java -Xms64m -Xmx64m sets the minimum and maximum heap sixe to 64mb.
Also it looks like you may be creating a lot of objects in your code, (extensive use of the new operator) maybe you can try using an object pool, this will not only help manage your memnory problems but will also improve the performance of your application because object creation is a relativley time expensive task, using object pools you can create all the objects you want as our app initialises, slower starup time but improved running performance.