compact1, compact2, compact3

java.lang.ref

Class Reference<T>

java.lang.Object

java.lang.ref.Reference<T>

Direct Known Subclasses:

PhantomReference, SoftReference, WeakReference

public abstract class Reference<T>
extends Object

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.

Since:

1.2

Method Summary

Modifier and Type	Method and Description
void	clear() Clears this reference object.
protected Object	clone() Throws CloneNotSupportedException.
boolean	enqueue() Clears this reference object and adds it 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.

Methods inherited from class java.lang.Object

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

Method Detail

get

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. JamaicaVM: implements this as native function to perform required synchronization with GC. JamaicaVM: Instances of Reference that are eligible for finalization whose referent is also eligible for finalization may get cleared by JamaicaVM without being enqueued. This ensures that weak or soft references that have a Object.finalize() method or are reachable from an object that has a Object.finalize() method will not prevent the GC from reclaiming the referent's memory.

Returns:

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

clear

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.

isEnqueued

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

enqueue

public boolean enqueue()

Clears this reference object and adds it 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

clone

protected Object clone()
                throws CloneNotSupportedException

Throws CloneNotSupportedException. A Reference cannot be meaningfully cloned. Construct a new Reference instead.

Overrides:

clone in class Object

Throws:

CloneNotSupportedException - always

API Note:

This method is defined in Java SE 8 Maintenance Release 4.

Returns:

never returns normally

Since:

8

See Also:

Cloneable