E - the type of elements held in this collectionpublic class DelayQueue<E extends Delayed> extends AbstractQueue<E> implements 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. 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. The Iterator provided in method iterator() is not guaranteed to traverse the elements of the DelayQueue in any particular order.
This class is a member of the Java Collections Framework.
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.
c - the collection of elements to initially containNullPointerException - if the specified collection or any of its elements are nullpublic boolean add(E e)
Inserts the specified element into this delay queue.
add in interface Collection<E extends Delayed>
add in interface BlockingQueue<E extends Delayed>
add in interface Queue<E extends Delayed>
add in class AbstractQueue<E extends Delayed>
e - the element to addtrue (as specified by Collection.add(E))NullPointerException - if the specified element is nullpublic boolean offer(E e)
Inserts the specified element into this delay queue.
offer in interface BlockingQueue<E extends Delayed>
offer in interface Queue<E extends Delayed>
e - the element to addtrueNullPointerException - if the specified element is nullpublic void put(E e)
Inserts the specified element into this delay queue. As the queue is unbounded this method will never block.
put in interface BlockingQueue<E extends Delayed>
e - the element to addNullPointerException - if the specified element is nullpublic boolean offer(E e,
long timeout,
TimeUnit unit) Inserts the specified element into this delay queue. As the queue is unbounded this method will never block.
offer in interface BlockingQueue<E extends Delayed>
e - the element to addtimeout - This parameter is ignored as the method never blocksunit - This parameter is ignored as the method never blockstrueNullPointerException - if the specified element is nullpublic E poll()
Retrieves and removes the head of this queue, or returns null if this queue has no elements with an expired delay.
poll in interface Queue<E extends Delayed>
null if this queue has no elements with an expired delaypublic E take()
throws InterruptedException Retrieves and removes the head of this queue, waiting if necessary until an element with an expired delay is available on this queue.
take in interface BlockingQueue<E extends Delayed>
InterruptedException - if interrupted while waitingpublic E poll(long timeout,
TimeUnit unit)
throws InterruptedException 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.
poll in interface BlockingQueue<E extends Delayed>
timeout - how long to wait before giving up, in units of unit
unit - a TimeUnit determining how to interpret the timeout parameternull if the specified waiting time elapses before an element with an expired delay becomes availableInterruptedException - if interrupted while waitingpublic E peek()
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.
peek in interface Queue<E extends Delayed>
null if this queue is emptypublic int size()
Description copied from interface: Collection
Returns the number of elements in this collection. If this collection contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.
size in interface Collection<E extends Delayed>
size in class AbstractCollection<E extends Delayed>
public int drainTo(Collection<? super E> c)
Description copied from interface: BlockingQueue
Removes all available elements from this queue and adds them to 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.
drainTo in interface BlockingQueue<E extends Delayed>
c - the collection to transfer elements intoUnsupportedOperationException - if addition of elements is not supported by the specified collectionClassCastException - if the class of an element of this queue prevents it from being added to the specified collectionNullPointerException - if the specified collection is nullIllegalArgumentException - if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collectionpublic int drainTo(Collection<? super E> c,
int maxElements) Description copied from interface: BlockingQueue
Removes at most the given number of available elements from this queue and adds them to 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.
drainTo in interface BlockingQueue<E extends Delayed>
c - the collection to transfer elements intomaxElements - the maximum number of elements to transferUnsupportedOperationException - if addition of elements is not supported by the specified collectionClassCastException - if the class of an element of this queue prevents it from being added to the specified collectionNullPointerException - if the specified collection is nullIllegalArgumentException - if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collectionpublic void clear()
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.
clear in interface Collection<E extends Delayed>
clear in class AbstractQueue<E extends Delayed>
public int remainingCapacity()
Always returns Integer.MAX_VALUE because a DelayQueue is not capacity constrained.
remainingCapacity in interface BlockingQueue<E extends Delayed>
Integer.MAX_VALUEpublic 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. (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.
toArray in interface Collection<E extends Delayed>
toArray in class AbstractCollection<E extends Delayed>
public <T> 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 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().toArray in interface Collection<E extends Delayed>
toArray in class AbstractCollection<E extends Delayed>
T - the runtime type of the array to contain the collectiona - the array into which the elements of the queue are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purposeArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this queueNullPointerException - if the specified array is nullpublic 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.
remove in interface Collection<E extends Delayed>
remove in interface BlockingQueue<E extends Delayed>
remove in class AbstractCollection<E extends Delayed>
o - element to be removed from this collection, if presenttrue if an element was removed as a result of this callpublic Iterator<E> iterator()
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 weakly consistent.
iterator in interface Iterable<E extends Delayed>
iterator in interface Collection<E extends Delayed>
iterator in class AbstractCollection<E extends Delayed>
© 1993–2017, Oracle and/or its affiliates. All rights reserved.
Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.