Get all th loaded classes

Question

Dear ppl,
I have been trying so hard to get a solution to the following problem:
I needed to know the name of the classes currently loaded in the jvm in a dynamic fashion ie any time I should be able to query jvm and get the list of currently loaded classes (which should not show the unloaded classes). I wanted to keep it simple so I avoided using jpda api. I found an article in java world which says:
If you really insist on monitoring classes loaded by absolutely every possible classloader in the JVM, it is hard to do so in pure Java.
You might try forcing every classloader instance to register itself in some global data structure. For example, if you modify both java.lang.ClassLoader constructors:
    protected ClassLoader() {
    SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkCreateClassLoader();
    this.parent = getSystemClassLoader();
    initialized = true;
    ClassLoaderRegistry.register (this);
    protected ClassLoader(ClassLoader parent) {
    ClassLoaderRegistry.register (this);
to call into the following class:
public abstract class ClassLoaderRegistry
    public static void register (final ClassLoader loader)
        if (loader != null)
            synchronized (CLASSLOADER_SET)
                CLASSLOADER_SET.put (loader, null);
    public static ClassLoader [] getClassLoaders ()
        final List /* ClassLoader */ resultList = new LinkedList ();
        synchronized (CLASSLOADER_SET)
            // We are using a weak map: be careful when traversing the key set
            // [it's unsafe to use resultList.addAll(CLASSLOADER_SET.keySet())]
            for (Iterator keys = CLASSLOADER_SET.keySet ().iterator (); keys.hasNext (); )
                // Note that WeakHashMap guarantees that the weak key will not be
                // cleared between hasNext() and next():
                resultList.add (keys.next ());
        final ClassLoader [] result = new ClassLoader [resultList.size ()];
        resultList.toArray (result);
        return result;
    // This field is used as a 'weak set' to avoid interfering with class
    // and classloader unloading and garbage collection:
    private static final WeakHashMap /* ClassLoader->null */ CLASSLOADER_SET
        = new WeakHashMap ();
} // End of class
you will in fact track every classloader instance created in the JVM. This happens because every classloader constructor eventually chains all the way down to one of the above two constructors. Then you can use ClassLoaderRegistry.getClassLoaders() followed by the usual ClassScope.getLoadedClasses() to get a full class listing snapshot.
Of course, you need to deploy both the modified java.lang.ClassLoader and ClassLoaderRegistry in the JVM's bootstrap classpath (using the -Xbootclasspath/p: JVM option) to make this work. This approach is probably only for dedicated Java hackers.
Now I did exactly what they said. But I get compile time error with the modified ClassLoader.
So now is there any other workaround? Can you please help me out?

Answer 1

hi,
Let me explain u in detail.
I have a JTextPane through which i load an image.Here is a code snippet
HTMLEditorKit kit = new HTMLEditorKit();
JTextPane jtp1=new JTextPane();
jtp1.setEditorKit(kit);
jtp1.setEditable(false);
jtp1.setSize(100,100);
jtp1.setText("<img src="top1.gif">");
I add this JTextPane jtp1 to a panel.There are two JTextPane holding different images which are added to apanel in turn.
When i add these(jtp1,jtp2) to a panel ,then i sometimes see the blank panel.jtp1 and jtp2 does not appear on that.
So what should i do so that only when all the components are loaded (here jtp1 and jtp2) then only my panel holding jtp1 and jtp2 is displayed.
Thank you
vineet