An interface implemented by objects that can be
cleaned up, which is to say, can release unneeded
object references. This is useful for many classes which
provide a pooling or caching function. Over time,
some pooled or cached objects may no longer be useful
to keep and can be released.
references to unneeded objects.
This interface is the bridge between
the JanitorThread class and an object that
wishes to be periodically told to "clean up".