Class ReferenceQueue<T>

java.lang.Object

java.lang.ref.ReferenceQueue<T>

Type Parameters:: T - the type of the reference object

public class ReferenceQueue<T> extends Object

Reference queues, to which registered reference objects are appended by the garbage collector after the appropriate reachability changes are detected.

Memory consistency effects: The enqueueing of a reference to a queue (by the garbage collector, or by a successful call to Reference.enqueue()) happens-before the reference is removed from the queue by poll() or remove(long).

Since:: 1.2

Constructor Summary

Constructor	Description
`ReferenceQueue()`	Constructs a new reference-object queue.

Method Summary

Modifier and Type	Method	Description
`Reference<? extends T>`	`poll()`	Polls this queue to see if a reference object is available.
`Reference<? extends T>`	`remove()`	Removes the next reference object in this queue, blocking until one becomes available.
`Reference<? extends T>`	`remove(long timeout)`	Removes the next reference object in this queue, blocking until either one becomes available or the given timeout period expires.

Methods declared in class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

ReferenceQueue

public ReferenceQueue()

Constructs a new reference-object queue.

Method Details

poll

public Reference<? extends T> poll()

Polls this queue to see if a reference object is available. If one is available without further delay then it is removed from the queue and returned. Otherwise this method immediately returns null.

Returns:

A reference object, if one was immediately available, otherwise null

See Also:

remove

public Reference<? extends T> remove(long timeout) throws InterruptedException

Removes the next reference object in this queue, blocking until either one becomes available or the given timeout period expires.

This method does not offer real-time guarantees: It schedules the timeout as if by invoking the Object.wait(long) method.

Parameters:

timeout - If positive, block for up to timeout milliseconds while waiting for a reference to be added to this queue. If zero, block indefinitely.

Returns:

A reference object, if one was available within the specified timeout period, otherwise null

Throws:

IllegalArgumentException - If the value of the timeout argument is negative

InterruptedException - If the timeout wait is interrupted

See Also:

remove

public Reference<? extends T> remove() throws InterruptedException

Removes the next reference object in this queue, blocking until one becomes available.

Returns:

A reference object, blocking until one becomes available

Throws:

InterruptedException - If the wait is interrupted

See Also:

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https://docs.oracle.com/en/java/javase/25/docs/api/java.base/java/lang/ref/ReferenceQueue.html