Class PhantomReference<T>

Phantom reference objects, which are enqueued after the collector determines that their referents may otherwise be reclaimed. Phantom references are most often used for scheduling pre-mortem cleanup actions in a more flexible way than is possible with the Java finalization mechanism.

If the garbage collector determines at a certain point in time that the referent of a phantom reference is phantom reachable, then at that time or at some later time it will enqueue the reference.

In order to ensure that a reclaimable object remains so, the referent of a phantom reference may not be retrieved: The get method of a phantom reference always returns null.

Unlike soft and weak references, phantom references are not automatically cleared by the garbage collector as they are enqueued. An object that is reachable via phantom references will remain so until all such references are cleared or themselves become unreachable.

Constructors

PhantomReference

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

Parameters:

referent - the object the new phantom reference will refer to

q - the queue with which the reference is to be registered, or null if registration is not required

Methods

get

public T get()

Returns this reference object's referent. Because the referent of a phantom reference is always inaccessible, this method always returns null.

Overrides:

get in class Reference<T>

Returns:

null