Name: bsC130419 Date: 08/22/2001


java version "1.4.0-beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-beta-b65)
Java HotSpot(TM) Client VM (build 1.4.0-beta-b65, mixed mode)


I imagine this is already fixed in your internal betas, but just in case...

Dialogs in the 1.4 beta never become garbage collectable. Conveniently, the
1.4 beta also won't let me use hprof, so I can't trace the pointer chain and
figure out why.

The following test case demonstrates the problem:

---

import javax.swing.*;

class TestDialog extends JDialog {
    String name;
    
    public TestDialog(String name) {
        this.name = name;
    }
    
    
    public void show() {
        super.show();
        dispose(); // so no user interaction is needed
    }
    
        
    public void finalize() {
        System.out.println(name + " being finalized");
    }
}


public class TestCase {
    public static void main(String[] arg) {
        TestDialog dialog1 = new TestDialog("Dialog1");
        TestDialog dialog2 = new TestDialog("Dialog2");
        TestDialog dialog3 = new TestDialog("Dialog3");
        
        // do nothing to Dialog1
        
        // pack Dialog2
        dialog2.pack();
        dialog2.dispose();
        
        // show Dialog3
        dialog3.show();
        
        // should be garbage collectable after this
        dialog1 = null;
        dialog2 = null;
        dialog3 = null;
        
        for (int i = 0; i < 20; i++)
            System.gc();
        
        System.exit(0);
    }
}

---

It works fine in JDK 1.3.1. In JDK 1.4 beta, only Dialog1 is ever finalized.
This means that any dialog box which is ever shown (or even packed) can never
become garbage collectable, leading to a huge memory leak.
(Review ID: 130385)
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I tried the attached new sample program with 1.4.0fcs, this issue seems
to happen.

1. Reproducing

 1) Compile the new sample program(Fd2.java)
 2) Invoke "java Fd2"
    -> you will see a frame which has "Show Child Dialog" and "Cancel"
       buttons.
 3) Click the "Show Child Button"
    -> you will see a frame which has "File Dialogue" and "Cancel"
       buttons.
 4) Click the "File Dialogue"
    -> you will see a file dialogue for file selection.
 5) Click the "Cancel" button in the file dialogue which appeared
    at the 4) opearation.
 6) Click the "Cancel" button on the frame which appeared at 3).
    -> you will be aware that you returns 2).
 7) Repeat from 2) to 6) for many times.
 8) Finally, you will see the following messages in the command prompt
    window and opration freezed.

total=66650112byte,free=3621592byte
total=66650112byte,free=2014104byte
total=66650112byte,free=1974888byte
total=66650112byte,free=367736byte
total=66650112byte,free=328968byte
java.lang.OutOfMemoryError
total=66650112byte,free=291808byte
java.lang.OutOfMemoryError


2. Configration

  MPU: Pentium IV 1.4[GHz]
  Mem: 384[MB]
  OS : Windows2000 SP2 (Japanese)
  JDK: 1.4.0fcs

java version "1.4.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-b92)
Java HotSpot(TM) Client VM (build 1.4.0-b92, mixed mode)

3. Note
  - I attached an image file(leak.jpg) which shows how the memory becomes
    short as a sample.
    This is the result with OptimizeIt4.11.
  - How many time should we repeat the 2)-6) loop in the above process ?
    It depends on each platform.
    With my PC, I repeated 50 times or so.

2002-03-26
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