Skip to content

Most visited

Recently visited

navigation
Added in API level 1

PhantomReference

public class PhantomReference
extends Reference<T>

java.lang.Object
   ↳ java.lang.ref.Reference<T>
     ↳ java.lang.ref.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.

Summary

Public constructors

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.

Public methods

T get()

Returns this reference object's referent.

Inherited methods

From class java.lang.ref.Reference
From class java.lang.Object

Public constructors

PhantomReference

Added in API level 1
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.

Parameters
referent T: the object the new phantom reference will refer to
q ReferenceQueue: the queue with which the reference is to be registered, or null if registration is not required

Public methods

get

Added in API level 1
T get ()

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

Returns
T null
This site uses cookies to store your preferences for site-specific language and display options.

Hooray!

This class requires API level or higher

This doc is hidden because your selected API level for the documentation is . You can change the documentation API level with the selector above the left navigation.

For more information about specifying the API level your app requires, read Supporting Different Platform Versions.