T
- the type of the referentpublic non-sealed 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 null
. The refersTo
method can be used to test whether some object is the referent of a phantom reference.
Constructor | Description |
---|---|
PhantomReference |
Creates a new phantom reference that refers to the given object and is registered with the given queue. |
clear, clone, enqueue, isEnqueued, reachabilityFence, refersTo
public PhantomReference(T referent, ReferenceQueue<? super T> q)
It is possible to create a phantom reference with a null
queue. Such a reference will never be enqueued.
referent
- the object the new phantom reference will refer toq
- the queue with which the reference is to be registered, or null
if registration is not requiredpublic T get()
null
.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/ref/PhantomReference.html