A doc bug here.

While debugging a memory leak in my platform application, I came to the realization that Children.Detachable.removeNotify() will only be called once the Children object is no longer strongly referenced, because the Nodes system uses the Active Reference Queue to figure out when to call removeNotify(). This makes Detachable.removeNotify() useless for detaching listeners, since any listener will keep the Children object referenced until removed, preventing removeNotify() from being called in the first place.

As it turns out, someone already realized this in the case of Children.removeNotify(), in https://netbeans.org/bugzilla/show_bug.cgi?id=99895 ("It seems I'll need to add a big fat warning into the removeNotify() javadoc.").

My suggestion is to add the same warning to Children.Detachable.removeNotify(), which is called under the same circumstances (via org.openide.nodes.SynchChildren). The warning from Children.removeNotify() currently reads: "Note that this is usually not the best place for unregistering listeners, etc., as listeners usually keep the child nodes in memory, preventing them from being collected, thus preventing this method to be called in the first place."