Android
java.util.concurrent
public class

java.util.concurrent.DelayQueue<E extends java.util.concurrent.Delayed>

java.lang.Object
java.util.AbstractCollection<E> Collection<E>
java.util.AbstractQueue<E> Queue<E>
java.util.concurrent.DelayQueue<E extends java.util.concurrent.Delayed> BlockingQueue<E>

An unbounded blocking queue of Delayed elements, in which an element can only be taken when its delay has expired. The head of the queue is that Delayed element whose delay expired furthest in the past - if no delay has expired there is no head and poll will return null. This queue does not permit null elements.

This class implements all of the optional methods of the Collection and Iterator interfaces.

Summary

Public Constructors

            DelayQueue()
Creates a new DelayQueue that is initially empty.
            DelayQueue(Collection<? extends E> c)
Creates a DelayQueue initially containing the elements of the given collection of Delayed instances.

Public Methods

          boolean  add(E o)
Adds the specified element to this queue.
          void  clear()
Atomically removes all of the elements from this delay queue.
          int  drainTo(Collection<? super E> c, int maxElements)
Removes at most the given number of available elements from this queue and adds them into the given collection.
          int  drainTo(Collection<? super E> c)
Removes all available elements from this queue and adds them into the given collection.
          Iterator<E>  iterator()
Returns an iterator over the elements in this queue.
          boolean  offer(E o, long timeout, TimeUnit unit)
Inserts the specified element into this delay queue.
          boolean  offer(E o)
Inserts the specified element into this delay queue.
          peek()
Gets but not removes the element in the head of the queue, or throws exception if there is no element in the queue.
          poll(long time, TimeUnit unit)
Retrieves and removes the head of this queue, waiting if necessary up to the specified wait time if no elements are present on this queue.
          poll()
Gets and removes the element in the head of the queue, or returns null if there is no element in the queue.
          void  put(E o)
Adds the specified element to this delay queue.
          int  remainingCapacity()
Always returns Integer.MAX_VALUE because a DelayQueue is not capacity constrained.
          boolean  remove(Object o)
Removes the first occurrence of the specified object from this Collection.
          int  size()
Returns the number of elements in this Collection.
          take()
Retrieves and removes the head of this queue, waiting if no elements are present on this queue.
        <T>  T[]  toArray(T[] array)
Returns an array containing all elements contained in this Collection.
          Object[]  toArray()
Returns a new array containing all elements contained in this Collection.
Methods inherited from class java.util.AbstractQueue
Methods inherited from class java.util.AbstractCollection
Methods inherited from class java.lang.Object
Methods inherited from interface java.lang.Iterable
Methods inherited from interface java.util.Collection
Methods inherited from interface java.util.Queue
Methods inherited from interface java.util.concurrent.BlockingQueue

Details

Public Constructors

public DelayQueue()

Creates a new DelayQueue that is initially empty.

public DelayQueue(Collection<? extends E> c)

Creates a DelayQueue initially containing the elements of the given collection of Delayed instances.

Parameters

c the collection

Throws

NullPointerException if c or any element within it is null

Public Methods

public boolean add(E o)

Adds the specified element to this queue.

Parameters

o the element to add

Returns

  • true (as per the general contract of Collection.add).

Throws

NullPointerException if the specified element is null.

public void clear()

Atomically removes all of the elements from this delay queue. The queue will be empty after this call returns.

public int drainTo(Collection<? super E> c, int maxElements)

Removes at most the given number of available elements from this queue and adds them into the given collection. A failure encountered while attempting to add elements to collection c may result in elements being in neither, either or both collections when the associated exception is thrown. Attempts to drain a queue to itself result in IllegalArgumentException. Further, the behavior of this operation is undefined if the specified collection is modified while the operation is in progress.

public int drainTo(Collection<? super E> c)

Removes all available elements from this queue and adds them into the given collection. This operation may be more efficient than repeatedly polling this queue. A failure encountered while attempting to add elements to collection c may result in elements being in neither, either or both collections when the associated exception is thrown. Attempts to drain a queue to itself result in IllegalArgumentException. Further, the behavior of this operation is undefined if the specified collection is modified while the operation is in progress.

public Iterator<E> iterator()

Returns an iterator over the elements in this queue. The iterator does not return the elements in any particular order. The returned iterator is a thread-safe "fast-fail" iterator that will throw ConcurrentModificationException upon detected interference.

Returns

  • an iterator over the elements in this queue.

public boolean offer(E o, long timeout, TimeUnit unit)

Inserts the specified element into this delay queue. As the queue is unbounded this method will never block.

Parameters

o the element to add
timeout This parameter is ignored as the method never blocks
unit This parameter is ignored as the method never blocks

Returns

  • true

Throws

NullPointerException if the specified element is null.

public boolean offer(E o)

Inserts the specified element into this delay queue.

Parameters

o the element to add

Returns

  • true

Throws

NullPointerException if the specified element is null.

public E peek()

Gets but not removes the element in the head of the queue, or throws exception if there is no element in the queue.

public E poll(long time, TimeUnit unit)

Retrieves and removes the head of this queue, waiting if necessary up to the specified wait time if no elements are present on this queue.

public E poll()

Gets and removes the element in the head of the queue, or returns null if there is no element in the queue.

public void put(E o)

Adds the specified element to this delay queue. As the queue is unbounded this method will never block.

Parameters

o the element to add

Throws

NullPointerException if the specified element is null.

public int remainingCapacity()

Always returns Integer.MAX_VALUE because a DelayQueue is not capacity constrained.

Returns

  • Integer.MAX_VALUE

public boolean remove(Object o)

Removes the first occurrence of the specified object from this Collection. This operation traverses over the collection, looking for the specified object. Once the object is found, the object will be removed from the collection using the iterator's remove method. This collection will throw an UnsupportedOperationException if the iterator returned does not implement remove method, and the specified object is in this collection.

Parameters

o the object to remove

Returns

  • true if this Collection is modified, false otherwise

public int size()

Returns the number of elements in this Collection.

Returns

  • the number of elements in this Collection

public E take()

Retrieves and removes the head of this queue, waiting if no elements are present on this queue.

public T[] toArray(T[] array)

Returns an array containing all elements contained in this Collection. If the specified array is large enough to hold the elements, the specified array is used, otherwise an array of the same type is created. If the specified array is used and is larger than this Collection, the array element following the collection elements is set to null.

Parameters

array the array

Returns

  • an array of the elements from this Collection

public Object[] toArray()

Returns a new array containing all elements contained in this Collection. All the elements in the array will not be referenced by the collection. The elements in the returned array will be sorted to the same order as those returned by the iterator of this collection itself if the collection guarantees the order.

Returns

  • an array of the elements from this Collection
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