Finally, how important is it to be able to unregister a cleaner? In all the years we've had sun.misc.Cleaner that capability has never been needed, and leaving it out would simplify the API.
I see this as having two big potential benefits (I'll let Roger confirm whether the implementation provides both):
- Resource release for finalizable objects is generally coded in two places; in the explicit close() / release() method, which we hope people will use, and in the finalizer, in case the object is collected without being closed. Having two ways to express the same action is error-prone; if there's one definition of "release the houn^H^H^H^Hresources" then they can't get out of sync.
This requires an atomic means to say "unregister the cleaner, and, if its not yet been run, run it now".
- If you can unregister the cleaner on the happy path (where the user explicitly closes the object ), then all the enqueue / reference processing / finalization work can be optimized away.
