See: Description
| Class | Description | 
|---|---|
| Reference<T> | Abstract base class for reference objects. | 
| ReferenceQueue<T> | Reference queues, to which registered reference objects are appended by the garbage collector
 after the appropriate reachability changes are detected. | 
| WeakReference<T> | Weak reference objects, which do not prevent their referents from being made finalizable,
 finalized, and then reclaimed. |