"bstansberry(a)jboss.com" wrote : Oh, but my class above is intended to be passed as a key to WeakHashMap. The ReferenceQueue polling will remove the only strong ref to the Key, at which point the WeakHashMap will do its normal thing and make the Key/value pair eligible for removal. Hmmm ... trying to put your code into real life showed some issues. The way you do your refQueue is wrong. :-) And I don't see how you can do it right. Since what you have to pass into WeakReference as Queue instance is the initial queue of actual type of your WeakReference - the type that's gonna be GCed - in our case the Class ref. But in that case we cannot do this | private void cleanKeyRefs() | { | Reference ref = null; | while ((ref = refQueue.poll()) != null) | { | ((KeyRef) ref).key = null; | } | } | I'll try to do WeakCompositeKeyMap, doing something similar as what we do in WeakValueHashMap. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4152343#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...