public class: PhantomReference
Direct Known Subclasses:
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
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.
Mark - Reinhold
public PhantomReference(T referent,
ReferenceQueue<? super T> q)
Creates a new phantom reference that refers to the given object and
is registered with the given queue.
It is possible to create a phantom reference with a null
queue, but such a reference is completely useless: Its get
method will always return null and, since it does not have a queue, it
will never be enqueued.
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
|Method from java.lang.ref.PhantomReference Summary:|
|Methods from java.lang.Object:|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait|
|Method from java.lang.ref.PhantomReference Detail:|
public T get()
Returns this reference object's referent. Because the referent of a
phantom reference is always inaccessible, this method always returns