| java.util.concurrent.DelayQueue
| DelayQueue | | public class DelayQueue extends AbstractQueue implements BlockingQueue<E>(Code) | | An unbounded
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. Expiration occurs when an element's
getDelay(TimeUnit.NANOSECONDS) method returns a value less
than or equal to zero. Even though unexpired elements cannot be
removed using take or poll, they are otherwise
treated as normal elements. For example, the size method
returns the count of both expired and unexpired elements.
This queue does not permit null elements.
This class and its iterator implement all of the
optional methods of the
Collection and
Iterator interfaces.
This class is a member of the
Java Collections Framework.
since:
1.5
author:
Doug Lea<
Parameters:
E - > the type of elements held in this collection |
| Constructor Summary | |
| 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. |
| Method Summary | |
| public boolean | add(E e)
Inserts the specified element into this delay queue. | | public void | clear()
Atomically removes all of the elements from this delay queue. | | public int | drainTo(Collection<? super E> c)
| | public int | drainTo(Collection<? super E> c, int maxElements)
| | public Iterator<E> | iterator()
Returns an iterator over all the elements (both expired and
unexpired) in this queue. | | public boolean | offer(E e)
Inserts the specified element into this delay queue. | | public boolean | offer(E e, long timeout, TimeUnit unit)
Inserts the specified element into this delay queue. | | public E | peek()
Retrieves, but does not remove, the head of this queue, or
returns null if this queue is empty. | | public E | poll()
Retrieves and removes the head of this queue, or returns null
if this queue has no elements with an expired delay. | | public E | poll(long timeout, TimeUnit unit)
Retrieves and removes the head of this queue, waiting if necessary
until an element with an expired delay is available on this queue,
or the specified wait time expires. | | public void | put(E e)
Inserts the specified element into this delay queue. | | public int | remainingCapacity()
Always returns Integer.MAX_VALUE because
a DelayQueue is not capacity constrained. | | public boolean | remove(Object o)
Removes a single instance of the specified element from this
queue, if it is present, whether or not it has expired. | | public int | size()
| | public E | take()
Retrieves and removes the head of this queue, waiting if necessary
until an element with an expired delay is available on this queue. | | public Object[] | toArray()
Returns an array containing all of the elements in this queue.
The returned array elements are in no particular order.
The returned array will be "safe" in that no references to it are
maintained by this queue. | | public T[] | toArray(T[] a)
Returns an array containing all of the elements in this queue; the
runtime type of the returned array is that of the specified array.
The returned array elements are in no particular order.
If the queue fits in the specified array, it is returned therein.
Otherwise, a new array is allocated with the runtime type of the
specified array and the size of this queue.
If this queue fits in the specified array with room to spare
(i.e., the array has more elements than this queue), the element in
the array immediately following the end of the queue is set to
null.
Like the
DelayQueue.toArray() method, this method acts as bridge between
array-based and collection-based APIs. |
| DelayQueue | | public DelayQueue()(Code) | | Creates a new DelayQueue that is initially empty.
|
| DelayQueue | | public DelayQueue(Collection<? extends E> c)(Code) | | Creates a DelayQueue initially containing the elements of the
given collection of
Delayed instances.
Parameters:
c - the collection of elements to initially contain
throws:
NullPointerException - if the specified collection or anyof its elements are null |
| add | | public boolean add(E e)(Code) | | Inserts the specified element into this delay queue.
Parameters:
e - the element to add true (as specified by Collection.add)
throws:
NullPointerException - if the specified element is null |
| clear | | public void clear()(Code) | | Atomically removes all of the elements from this delay queue.
The queue will be empty after this call returns.
Elements with an unexpired delay are not waited for; they are
simply discarded from the queue.
|
| iterator | | public Iterator<E> iterator()(Code) | | Returns an iterator over all the elements (both expired and
unexpired) in this queue. The iterator does not return the
elements in any particular order. The returned
Iterator is a "weakly consistent" iterator that will
never throw
ConcurrentModificationException , and
guarantees to traverse elements as they existed upon
construction of the iterator, and may (but is not guaranteed
to) reflect any modifications subsequent to construction.
an iterator over the elements in this queue |
| offer | | public boolean offer(E e)(Code) | | Inserts the specified element into this delay queue.
Parameters:
e - the element to add true
throws:
NullPointerException - if the specified element is null |
| offer | | public boolean offer(E e, long timeout, TimeUnit unit)(Code) | | Inserts the specified element into this delay queue. As the queue is
unbounded this method will never block.
Parameters:
e - the element to add
Parameters:
timeout - This parameter is ignored as the method never blocks
Parameters:
unit - This parameter is ignored as the method never blocks true
throws:
NullPointerException - |
| peek | | public E peek()(Code) | | Retrieves, but does not remove, the head of this queue, or
returns null if this queue is empty. Unlike
poll, if no expired elements are available in the queue,
this method returns the element that will expire next,
if one exists.
the head of this queue, or null if thisqueue is empty. |
| poll | | public E poll()(Code) | | Retrieves and removes the head of this queue, or returns null
if this queue has no elements with an expired delay.
the head of this queue, or null if thisqueue has no elements with an expired delay |
| poll | | public E poll(long timeout, TimeUnit unit) throws InterruptedException(Code) | | Retrieves and removes the head of this queue, waiting if necessary
until an element with an expired delay is available on this queue,
or the specified wait time expires.
the head of this queue, or null if thespecified waiting time elapses before an element withan expired delay becomes available
throws:
InterruptedException - |
| put | | public void put(E e)(Code) | | Inserts the specified element into this delay queue. As the queue is
unbounded this method will never block.
Parameters:
e - the element to add
throws:
NullPointerException - |
| remainingCapacity | | public int remainingCapacity()(Code) | | Always returns Integer.MAX_VALUE because
a DelayQueue is not capacity constrained.
Integer.MAX_VALUE |
| remove | | public boolean remove(Object o)(Code) | | Removes a single instance of the specified element from this
queue, if it is present, whether or not it has expired.
|
| take | | public E take() throws InterruptedException(Code) | | Retrieves and removes the head of this queue, waiting if necessary
until an element with an expired delay is available on this queue.
the head of this queue
throws:
InterruptedException - |
| toArray | | public Object[] toArray()(Code) | | Returns an array containing all of the elements in this queue.
The returned array elements are in no particular order.
The returned array will be "safe" in that no references to it are
maintained by this queue. (In other words, this method must allocate
a new array). The caller is thus free to modify the returned array.
This method acts as bridge between array-based and collection-based
APIs.
an array containing all of the elements in this queue |
| toArray | | public T[] toArray(T[] a)(Code) | | Returns an array containing all of the elements in this queue; the
runtime type of the returned array is that of the specified array.
The returned array elements are in no particular order.
If the queue fits in the specified array, it is returned therein.
Otherwise, a new array is allocated with the runtime type of the
specified array and the size of this queue.
If this queue fits in the specified array with room to spare
(i.e., the array has more elements than this queue), the element in
the array immediately following the end of the queue is set to
null.
Like the
DelayQueue.toArray() method, this method acts as bridge between
array-based and collection-based APIs. Further, this method allows
precise control over the runtime type of the output array, and may,
under certain circumstances, be used to save allocation costs.
The following code can be used to dump a delay queue into a newly
allocated array of Delayed:
Delayed[] a = q.toArray(new Delayed[0]);
Note that toArray(new Object[0]) is identical in function to
toArray().
Parameters:
a - the array into which the elements of the queue are tobe stored, if it is big enough; otherwise, a new array of thesame runtime type is allocated for this purpose an array containing all of the elements in this queue
throws:
ArrayStoreException - if the runtime type of the specified arrayis not a supertype of the runtime type of every element inthis queue
throws:
NullPointerException - if the specified array is null |
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