Problem: memory leak ?

Question

Hello,
I've created a swing program with internalframes. each internalframes has many objects
and uses a lot of memory. Each time a frame is closed i call disopse on it and i am 'sure'
that there are no more references to the internalframe.
So logically, i can open lots of iframes and close them all. The the memory usage bij java.exe
shoudl be teh same. But that is not the case. I saw garbage collects only frees memmory to
the JVM. But how do i know whether the objects are freed or not.
Should'nt the memory usage decrease when i close all the opened iframes????
The question: How do i know for sure if i do not have any references to an iframe so that the iframe can be collected by the garbage collector? The memory of the program keeps growing and growing if i open 10 frames, close all the frames and then do that all over again.
Help me!

Answer 1

Hi,
we had major problems with Swing components leaking memory.
Since Swing components have internal references to the child components, one container could
be leaking lots of memory.
NB : you must explicitely remove all listeners too, action listeners, mouse listeners etc.
Below is a very handy piece of code I wrote to explicitely remove all child components from an initial container. It's depth first recursive, and it certainly done wonders for us.
regards,
Owen
import java.awt.Container;
import java.awt.Component;
import javax.swing.RootPaneContainer;
public class ComponentCleaner
    public static void cleanComponent(Component baseComponent)
        try
            cleanComponent(baseComponent, 0);
        catch ( Exception ignore )
            // give some exception handling...
    * The "depth" parameter was being used for text output debugging.
    * But isn't essential now.  I'll keep it anyways, as it avoids
    * calling the garbage collector every recursion.
    protected static void cleanComponent(Component baseComponent,
                                         int depth)
        if (baseComponent == null) // recursion terminating clause
            return ;
        Container cont;
        Component[] childComponents;
        int numChildren;
        // clean up component containers
        if(baseComponent instanceof Container)
            // now clean up container instance variables
            if(baseComponent instanceof RootPaneContainer)
            { // Swing specialised container
                cont = (Container)baseComponent;
                numChildren = cont.getComponentCount();
                childComponents = cont.getComponents();
                for(int i = 0;i < numChildren;i++)
                    // remove each component from the current container
                    // each child component may be a container itself
                    cleanComponent(childComponents, depth + 1);
((RootPaneContainer)cont).getContentPane().remove(childComponents[i]);
((RootPaneContainer)cont).getContentPane().setLayout(null);
else
{ // General Swing, and AWT, Containers
cont = (Container)baseComponent;
numChildren = cont.getComponentCount();
childComponents = cont.getComponents();
for(int i = 0;i < numChildren;i++) //for(int i = 0;i < numChildren;i++)
// remove each component from the current container
// each child component may be a container itself
cleanComponent(childComponents[i], depth + 1);
cont.remove(childComponents[i]);
cont.setLayout(null);
} // if component is also a container