This Bugzilla instance is a read-only archive of historic NetBeans bug reports. To report a bug in NetBeans please follow the project's instructions for reporting issues.
Those methods (like it is e.g. on JComponent) would be useful to check whether some listener is already registered at node (object in general), and in behave afterwards according the result, i.e. not to register itself many times. I guess such methods would be useful also on other types of objects. Currently the abovementioned case is by-passed by weak listener technnique, (the new one is registered and the old one is deregistered while the hard ref to the old one is replaced by the one to the new listener). But that's not nice nither from performance (always new listener is created) nor from consistency point of view (until the garbage comes into play, there is more than one listener in the game).
Taking over the node bugs from phrebejk.
It would be big mistake to put such methost in API. First of all, you're responsible yourself for registering only once and you need no support from the event source. You don't even need the WeakListener most of the time and WeakListener won't help you in any way with multiple registrations. Second, it would allow you to gain access to other, unrelated, listeners and do strange things with them (fake event, unregistration of foreign listeners, ...)