java.lang.ref
Class WeakReference

java.lang.Object
  java.lang.ref.Reference
      java.lang.ref.WeakReference

Direct Known Subclasses:

AbstractActionPropertyChangeListener.OwnedWeakReference, GapContent.MarkData, ThreadLocal.ThreadLocalMap.Entry, WeakHashMap.Entry

public class WeakReference

extends Reference

Weak reference objects, which do not prevent their referents from being made finalizable, finalized, and then reclaimed. Weak references are most often used to implement canonicalizing mappings.

Suppose that the garbage collector determines at a certain point in time that an object is weakly reachable. At that time it will atomically clear all weak references to that object and all weak references to any other weakly-reachable objects from which that object is reachable through a chain of strong and soft references. At the same time it will declare all of the formerly weakly-reachable objects to be finalizable. At the same time or at some later time it will enqueue those newly-cleared weak references that are registered with reference queues.

Since:

1.2

Author:

Mark Reinhold

Nested Class Summary

Nested classes inherited from class java.lang.ref.Reference

Field Summary

Fields inherited from class java.lang.ref.Reference

next, queue

Constructor Summary

WeakReference(Object referent)
Creates a new weak reference that refers to the given object.

WeakReference(Object referent, ReferenceQueue q)
Creates a new weak reference that refers to the given object and is registered with the given queue.

Methods inherited from class java.lang.ref.Reference

clear, enqueue, get, isEnqueued

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

WeakReference

public WeakReference(Object referent)

Creates a new weak reference that refers to the given object. The new reference is not registered with any queue.

Parameters:

referent - object the new weak reference will refer to

WeakReference

public WeakReference(Object referent,
                     ReferenceQueue q)

Creates a new weak reference that refers to the given object and is registered with the given queue.

Parameters:

referent - object the new weak reference will refer to

q - queue the weak reference is registered with

Throws:

NullPointerException - If the queue argument is null