PhantomReference<T> | Implements a phantom reference, which is the weakest of the three types of references. |
Reference<T> | Provides an abstract class which describes behavior common to all reference objects. |
ReferenceQueue<T> |
The ReferenceQueue is the container on which reference objects are
enqueued when the garbage collector detects the reachability type specified
for the referent.
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SoftReference<T> | A reference that is cleared when its referent is not strongly reachable and there is memory pressure. |
WeakReference<T> | Implements a weak reference, which is the middle of the three types of references. |