public class PhantomReference<T> extends Reference<T>
Suppose the garbage collector determines at a certain point in time that an object is phantom reachable. At that time it will atomically clear all phantom references to that object and all phantom references to any other phantom-reachable objects from which that object is reachable. At the same time or at some later time it will enqueue those newly-cleared phantom references that are registered with reference queues.
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
|Constructor and Description|
Creates a new phantom reference that refers to the given object and is registered with the given queue.
|Modifier and Type||Method and Description|
Returns this reference object's referent.
public PhantomReference(T referent, ReferenceQueue<? super T> q)
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
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