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Memory leak in image display

Posted on 1997-07-31
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Last Modified: 2006-11-17
I have slideshow application that displays numerous images. However, after each image display more memory is taken by the program till after about 40 images the program runs out of memory and crashes.  I need to be able to clear the memory used by each previously displayed image.  I have tried g.dispose() and image.flush() with no results.  How do I reclaim the used memory?
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Question by:faust073197
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by:mann061997
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Remember that MediaTracker will maintain a reference to registered images - they can't be garbage collected until they are released or the Tracker object goes out of scope.
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by:faust073197
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I have tried it with elimination of the MediaTracker, with no effect... still how would one release a reference to a image in MediaTracker... just set it to null?
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by:faust073197
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Actually, here is a simple example of a program that illustrates my problem.  Each mouse click displays a new image, but each previous image still exists in memory.  After 40 or so the program runs out of memory and crashes.


import java.awt.*;
import java.util.*;
import java.io.*;

public class java_app extends Frame
{
      Image image;
      int x = 10;
      String simage = "back.jpg";
      Toolkit tk = Toolkit.getDefaultToolkit();
        
      public java_app(String title)
      {
            super(title);
      }

      public void main (String args[])
      {
        
            java_app application = new java_app("java_app");
            application.resize(300, 300);
            application.show();
      }
      public void paint(Graphics g)
      {
                 String simage =  "img00" + x + ".jpg";
             image =  tk.getImage(simage);
            g.drawImage(image, 0 , 0, this);
            Runtime info = Runtime.getRuntime();
            System.out.println("total memory= " + info.totalMemory());

            
      }

      public boolean mouseDown(Event evt, int xx, int yy)
{
            if (image != null)
            {image.flush();}
             repaint();
             System.out.println(simage + x);

             x++;
             repaint();
                 return true;
      }

}


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by:mann061997
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flush() only marks the image for deletion; it doesn't get removed until the next gc cycle. Try calling System.gc() after flush(). Does it make any difference?
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Expert Comment

by:arktur
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If you use Sun's JVM try to run your application with by calling "java -verbosegc your_application_class". You will be able to see when gc runs.
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by:faust073197
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i've tried running System.gc() right after the image.flush() with no result
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by:aleshka
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Try to run System.gc() after 'image = null'.
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adrianr091197 earned 150 total points
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This question has been answered, see the query "Images and flushing memory", answered by keisha on 09/09
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