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

    Constructors
    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
    Modifier and Type
    Method
    Description
    protected Object
    clone()
    Creates and returns a copy of this object.
    boolean
    equals(Object obj)
    Indicates whether some other object is "equal to" this one.
    protected void
    finalize()
    Deprecated, for removal: This API element is subject to removal in a future version.
    Finalization is deprecated and subject to removal in a future release.
    final Class<?>
    getClass()
    Returns the runtime class of this Object.
    int
    hashCode()
    Returns a hash code value for this object.
    final void
    notify()
    Wakes up a single thread that is waiting on this object's monitor.
    final void
    notifyAll()
    Wakes up all threads that are waiting on this object's monitor.
    String
    toString()
    Returns a string representation of the object.
    final void
    wait()
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
    final void
    wait(long timeoutMillis)
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
    final void
    wait(long timeoutMillis, int nanos)
    Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

  • 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: