Class PhantomReference<T>

java.lang.Object

java.lang.ref.Reference<T>

java.lang.ref.PhantomReference<T>

public non-sealed class PhantomReference<T>
extends Reference<T>

PhantomReference objects are used to detect referents which are no longer visible and are eligible to have their storage reclaimed.

Since:

JDK1.2

Constructor Summary

Constructors

Constructor	Description
PhantomReference(T r, ReferenceQueue<? super T> q)	Constructs a new instance of this class.

Method Summary

Modifier and Type	Method	Description
T	get()	Return the referent of the reference object.

Methods declared in class Reference

clear, clone, enqueue, isEnqueued, reachabilityFence, refersTo

Modifier and Type	Method	Description
void	clear()	Make the referent null.
protected Object	clone()	This method will always throw CloneNotSupportedException.
boolean	enqueue()	Force the reference object to be enqueued if it has been associated with a queue.
boolean	isEnqueued()	Deprecated. Use ReferenceQueue or Reference.refersTo(null).
static void	reachabilityFence(Object ref)	Used to keep the referenced object strongly reachable so that it is not reclaimable by garbage collection.
final boolean	refersTo(T target)	Does this object refer to target?

Methods declared in class Object

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

Modifier and Type	Method	Description
boolean	equals(Object o)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. May cause performance issues, deadlocks and hangs.
final Class<? extends Object>	getClass()	Answers the unique instance of java.lang.Class which represents the class of the receiver.
int	hashCode()	Answers an integer hash code for the receiver.
final void	notify()	Causes one thread which is waiting on the receiver to be made ready to run.
final void	notifyAll()	Causes all threads which are waiting on the receiver to be made ready to run.
String	toString()	Answers a string containing a concise, human-readable description of the receiver.
final void	wait()	Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
final void	wait(long time)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
final void	wait(long time, int frac)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

Constructor Details

PhantomReference

public PhantomReference(T r,
 ReferenceQueue<? super T> q)

Constructs a new instance of this class.

Parameters:

r - referent to track.

q - queue to register to the reference object with.

Method Details

get

public T get()

Return the referent of the reference object. Phantom reference objects referents are inaccessible, and so null is returned.

Overrides:

get in class Reference<T>

Returns:

Object Returns null.