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Java has several flavours, Phantom, Weak, Soft....

They each provide different runtime options. A Soft reference is more likely the thing one would want to use - it holds on the the underlying reference a bit longer, making it actually likely that next time you look, it will be there. The soft ref. will release its stuff before you get any Out Of Memory issues, however, so it's quite safe. My experience with the C# WeakRef is that it's highly likely to punt the object right away (like the Java class of the same name). The Phantom reference adds a lot more value which I wont bother explaining here.