OutOfMemoryError - how do I find out where the memory is going?

[Cate van Alphen]

Hi,

My program keeps giving an OutOfMemoryError. I was wondering if there were any tips to find out where the memory is going. I can't seem find a pattern to when it gives up the ghost. I have put a Static count variable into each of my classes which increments in the constructor and takes off one in the finalize method and prints out the count. This seems to be behaving as I expected ie. there is the correct number of each of my objects.

Thanks

[Masoud Kalali]

you can use profilers to find memory leak in your application (if you cannot figure it out by logging or tracing the code execution)

there are plenty of profilers available to java developers. one of them is Netbeans profiler (if you use netbeans you can use this profiler) im sure that thre are profilers for eclipse like jProiler and yourkit java profiler.

but for free you can use netbeans profiler from www.netbeans.org

[Cameron Wallace McKenzie]

Increase the heap size, dude. Just don't increase it too much.

Heap size. That's my trick. I know WebSphere Portal goes out of memory as soon as you turn it on if you don't boost the heap size up after installation.

-Cameron

[Stan James]

A couple easy ways to accidentally chew up all memory are recursive routines that forget to bottom out and return, and loops that forget to stop and keep creating objects. If your out of memory problems occur suddenly at startup or right after kicking off some operation, you might look for those situations.

With JDK 5 and later you get JConsole which will let you watch memory use and object instance counts. Those might give you a clue how fast the problem comes on and when it starts.

Of course it may be you don't have a coding bug at all, but just use a lot of memory. If that's the case you may be able to bump up the heap to handle it. Let us know what you find!

[Cate van Alphen]

Thanks everyone. I have tried some profilers and now I'm REALLY confused! I've tried JConsole and NetBeans. I'm a bit overwhelmed with the info from NetBeans, but it seems there are a lot of int[] from BufferedImage. My program is a sort of flower hybidising thing. I have a singleton class called FlowerSimState which holds all the information, and the panels of the gui are registered as observers. What's really confusing me is that if I press the button with the OffspringListener repeatedly (50 times), the memory usage constantly increases untill it dies. If I press the RandomListener button the memory fluctuates, but it calls the same function as the OffspringListener! If I press other buttons, the OffspringListener still kills the program but at a less predicatable rate.

I've included some code, but it's not all there as I tried to simplify to make it more readable. I only realise how confusing my code is when I try to explain it to someone else.

class OffspringListener implements ActionListener {
        public void actionPerformed ( ActionEvent e ) {
            FlowerSimState.getInstance().changeOffspring();   
        }
}
    
class RandomListener implements ActionListener {
        public void actionPerformed ( ActionEvent e ) {
            FlowerSimState.getInstance().makeRandomParents();
            FlowerSimState.getInstance().changeOffspring();
        }
}        

 
public class FlowerSimState implements Subject, Serializable {
    private static FlowerSimState instance = new FlowerSimState();
    private List< Observer > observers;
    
    private Color background;
    private FlowerPanel current;
    private FlowerPanel start;
    private Observer previous;
    private Flower[] parents;
    private Set<Flower> species;
    private ArrayList<Flower> offspring;
    private ArrayList<Flower> hybrid;
    private ArrayList<Flower> randomPool;
    private JFileChooser chooser;
 
    //more code here, I've tired to simplify...
 
    public static FlowerSimState getInstance( ) {
        return instance;    
    }
 
    public void notifyObservers(Change c){
            for ( Observer ob : observers ) {
                ob.change( c );
            } 
    }    
    
    public void makeRandomParents() {
        Random random = new Random();
                
        Flower f1 = randomPool.get( random.nextInt(randomPool.size()) );
        Flower f2 = randomPool.get( random.nextInt(randomPool.size()) );        
        parents[0] = f1.crossFlower( f2 );        
        
        f1 = randomPool.get( random.nextInt(randomPool.size()) );
        f2 = randomPool.get( random.nextInt(randomPool.size()) );
        parents[1] = f1.crossFlower( f2 );
        
        notifyObservers( Change.PARENT );
        if ( current != null ) { current.select(); }
    } 
    
    public void changeOffspring() {
        for ( int x = 0; x < offspring.size(); x++ ) {
        
            Flower f = offspring.get(x);
            int i = randomPool.indexOf( f );
                         
            f = parents[0].crossFlower( parents[1] );
            
            offspring.set( x, f );
            randomPool.set( i, f );
        }   
        notifyObservers( Change.OFFSPRING );
        current.select();
    }
    
    public Iterator<Flower> getOffspring () {
        return offspring.iterator();
    }
    
}   

 
public class ParentPanel extends JPanel implements Observer {
    FlowerPanel[] parents = new FlowerPanel[2];
    FlowerSimState state; 
 
//more setting up here... 
 
    public void change ( Change c ) {
        if ( c == Change.PARENT ) {
            Flower[] p = state.getParents();
            parents[0].changePic( p[0] );
            parents[1].changePic( p[1] );
        } 
    }     
}
 
class OffspringPanel extends JPanel implements Observer {
    FlowerSimState state;
    List<FlowerPanel> flowers; 
 
//more setting up here... 
 
    public void change ( Change c ) {
        switch ( c ) {
        case OFFSPRING: 
            Iterator<Flower> offspring = state.getOffspring();
            for ( int x = 0; x < flowers.size(); x++ ){
                flowers.get(x).changePic( offspring.next() );
            }
            break;  
        }
    }
}

 
public class FlowerPanel extends JPanel implements Observer {
    private Image image;
    private Flower flower;
 
//more code here
 
    public void paintComponent( Graphics g) {
g.drawImage(image,0,0,this);
}  
 
    public void changePic ( Flower f ) {
   flower = f;
   image = f.getImage();
   repaint();
} 
}

abstract class Flower implements Serializable, Comparable<Flower>{
    private String name = "";
    private DNA[] genome;
    private FamilyTree family = null;    
    private transient Image image = null;
//more code
    public Image getImage() { 
        if (image == null) {
            image = createImage();
        }
        return image;
    }    
 
    public Gene[] splitGenome() {
        Gene[] half = new Gene[ genome.length ];
        for ( int x = 0; x < genome.length; x++ ) {
            half[x] = genome[x].splitDNA();    
        }
        
        return half;
    }
 
//createImage and crossFlower are abstract, implemented in subclass
}
 
class Strep extends Flower {
 
    public Flower crossFlower( Flower f ){
        if ( f instanceof Strep ) {
            return new Strep( this, f );
        } else {
            return new Strep( this.splitGenome(), this.getName() );
        }         
    }
 
    public Image createImage() {
        Color background = FlowerSimState.getInstance().getBackground();
        ImageStencil stencil = new ImageStencil(110, 110, background );
        URL[] alphas = new URL[9];
        DNA[] genome = getGenome();        
        
        alphas[0] = Strep.class.getResource("images/basePetal.gif");
        alphas[1] = Strep.class.getResource("images/lowerBi.gif");
        alphas[2] = Strep.class.getResource("images/upperBi.gif");
        alphas[3] = Strep.class.getResource("images/throat.gif");
        alphas[4] = Strep.class.getResource("images/veins.gif");
        alphas[5] = Strep.class.getResource("images/lowerVein.gif");
        alphas[6] = Strep.class.getResource("images/upperVein.gif");
        alphas[7] = Strep.class.getResource("images/upperPoint.gif");
        alphas[8] = Strep.class.getResource("images/bars.gif"); 
        
        assert ( alphas[0] != null) : "Get Resource failure";
        
        stencil.add ( alphas[0], genome[0].getColor() );
        //Bi colour petals
        if ( genome[1].getVisible() ) {
            stencil.add( alphas[1], genome[1].getColor() );
        }
        if ( genome[2].getVisible() ) {
            stencil.add( alphas[2], genome[2].getColor() );
        }
        // if throat is not visible paint using lowerBi colour
        if ( genome[3].getVisible() ) {
            stencil.add( alphas[3], genome[3].getColor() );
        }
        else stencil.add( alphas[3], genome[1].getColor() ); 
        
        //veins
        if ( genome[4].getVisible() ) {
            stencil.add( alphas[4], genome[4].getColor() );
        
            //lower vein uses vein colour and is only visible if veins are present
            if ( genome[5].getVisible() ) {
                stencil.add( alphas[5], genome[4].getColor() );
            }
            //upper vein uses own colour, is only visible if veins are present
            if ( genome[6].getVisible() ) {
                stencil.add( alphas[6], genome[6].getColor() );
            }            
        }
        //points
        if ( genome[7].getVisible() ) {
            stencil.add( alphas[7], genome[7].getColor() );
        }
        //bars
        if ( genome[8].getVisible() ) {
            stencil.add( alphas[8], genome[8].getColor() );
        }
        
        return stencil.getImage();
    }
}

public class ImageStencil {
    BufferedImage image;
    int w, h;
        
    ImageStencil( int width, int height, Color background){
        w = width;
        h = height;
        
        image = new BufferedImage (w, h, BufferedImage.TYPE_INT_ARGB );
       
        if (background == null) background = new JPanel().getBackground();
        
        Graphics2D g = image.createGraphics();
        g.setColor( background );
        g.fillRect(0,0, width, height);
        
    }
    
    void add( URL f, Color c){
        //get pixels for mask shape
        Image shape = Toolkit.getDefaultToolkit().getImage(f);
        int[] pixels = new int[w * h];
        PixelGrabber pg = new PixelGrabber(shape, 0, 0, w, h, pixels, 0, w);
        try {
            pg.grabPixels();
        } catch (InterruptedException e) {
            System.err.println("interrupted waiting for pixels!");
            return;
        }
        
        //work through pixels of mask and change as appropriate
        for (int j = 0; j < h; j++) {
            for (int i = 0; i < w; i++) {
                Color pix = new Color( pixels[ j * w + i ] );
                
                if (pix.getRGB() > Color.BLACK.getRGB()) {
                    Color blend = ColorChange.colorBlend( 
                        c, new Color(image.getRGB(i, j)), pix);               
                    image.setRGB ( i, j, blend.getRGB());  
                }       
                
            }
        }
        
    }
    
    Image getImage() {return image;}
}
    

[Srinivas Kalvala]

Hello,

I have used JCONSOLE to save with this error OutOfMemoryException. It will good runtime analysis of your application.