Reference

public abstract class Reference extends Object

Known Direct Subclasses PhantomReference<T>, SoftReference<T>, WeakReference<T> PhantomReference<T> Phantom reference objects, which are enqueued after the collector determines that their referents may otherwise be reclaimed.  SoftReference<T> Soft reference objects, which are cleared at the discretion of the garbage collector in response to memory demand.  WeakReference<T> Weak reference objects, which do not prevent their referents from being made finalizable, finalized, and then reclaimed.

Abstract base class for reference objects. This class defines the operations common to all reference objects. Because reference objects are implemented in close cooperation with the garbage collector, this class may not be subclassed directly.

Public Method Summary

void	clear() Clears this reference object.
boolean	enqueue() Adds this reference object to the queue with which it is registered, if any.
T	get() Returns this reference object's referent.
boolean	isEnqueued() Tells whether or not this reference object has been enqueued, either by the program or by the garbage collector.

Protected Method Summary

void	finalize()

Inherited Method Summary

From class java.lang.Object

Object	clone()
boolean	equals(Object arg0)
void	finalize()
final Class<?>	getClass()
int	hashCode()
final void	notify()
final void	notifyAll()
String	toString()
final void	wait(long arg0, int arg1)
final void	wait(long arg0)
final void	wait()

Public Methods

public void clear ()

Clears this reference object. Invoking this method will not cause this object to be enqueued.

This method is invoked only by Java code; when the garbage collector clears references it does so directly, without invoking this method.

public boolean enqueue ()

Adds this reference object to the queue with which it is registered, if any.

This method is invoked only by Java code; when the garbage collector enqueues references it does so directly, without invoking this method.

Returns

• true if this reference object was successfully enqueued; false if it was already enqueued or if it was not registered with a queue when it was created

public T get ()

Returns this reference object's referent. If this reference object has been cleared, either by the program or by the garbage collector, then this method returns null.

Returns

• The object to which this reference refers, or null if this reference object has been cleared

public boolean isEnqueued ()

Tells whether or not this reference object has been enqueued, either by the program or by the garbage collector. If this reference object was not registered with a queue when it was created, then this method will always return false.

Returns

• true if and only if this reference object has been enqueued

Protected Methods

protected void finalize ()