@NonNullByDefault

# Package java.lang.ref

Contains core language classes related to object references & garbage collection.

- Class Summary
  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.