程序包 java.util.concurrent

类 DelayQueue<E extends Delayed>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractQueue<E>

java.util.concurrent.DelayQueue<E>

类型参数:

E - the type of elements held in this collection

所有已实现的接口:

Iterable<E>, Collection<E>, BlockingQueue<E>, Queue<E>

public class DelayQueue<E extends Delayed>
extends AbstractQueue<E>
implements BlockingQueue<E>

An unbounded BlockingQueue 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.

从以下版本开始:

1.5

构造器概要

构造器

构造器	说明
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.

方法概要

限定符和类型	方法	说明
boolean	add(E e)	Inserts the specified element into this delay queue.
void	clear()	Atomically removes all of the elements from this delay queue.
int	drainTo(Collection<? super E> c)	Removes all available elements from this queue and adds them to the given collection.
int	drainTo(Collection<? super E> c, int maxElements)	Removes at most the given number of available elements from this queue and adds them to the given collection.
Iterator<E>	iterator()	Returns an iterator over all the elements (both expired and unexpired) in this queue.
boolean	offer(E e)	Inserts the specified element into this delay queue.
boolean	offer(E e, long timeout, TimeUnit unit)	Inserts the specified element into this delay queue.
E	peek()	Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty.
E	poll()	Retrieves and removes the head of this queue, or returns null if this queue has no elements with an expired delay.
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.
void	put(E e)	Inserts the specified element into this delay queue.
int	remainingCapacity()	Always returns Integer.MAX_VALUE because a DelayQueue is not capacity constrained.
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.
int	size()	Returns the number of elements in this collection.
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.
Object[]	toArray()	Returns an array containing all of the elements in this queue.
<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.

从类继承的方法 java.util.AbstractCollection

contains, containsAll, isEmpty, removeAll, retainAll, toString

从类继承的方法 java.util.AbstractQueue

addAll, element, remove

从接口继承的方法 java.util.concurrent.BlockingQueue

contains

从接口继承的方法 java.util.Collection

addAll, containsAll, equals, hashCode, isEmpty, parallelStream, removeAll, removeIf, retainAll, spliterator, stream

从接口继承的方法 java.lang.Iterable

forEach

从类继承的方法 java.lang.Object

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

从接口继承的方法 java.util.Queue

element, remove

构造器详细资料

DelayQueue

public DelayQueue()

Creates a new DelayQueue that is initially empty.

DelayQueue

public DelayQueue(Collection<? extends E> c)

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

参数:

c - the collection of elements to initially contain

抛出:

NullPointerException - if the specified collection or any of its elements are null

方法详细资料

add

public boolean add(E e)

Inserts the specified element into this delay queue.

指定者:

add 在接口中 BlockingQueue<E extends Delayed>

指定者:

add 在接口中 Collection<E extends Delayed>

指定者:

add 在接口中 Queue<E extends Delayed>

覆盖:

add 在类中 AbstractQueue<E extends Delayed>

参数:

e - the element to add

返回:

true (as specified by Collection#add)

抛出:

NullPointerException - if the specified element is null

offer

public boolean offer(E e)

Inserts the specified element into this delay queue.

指定者:

offer 在接口中 BlockingQueue<E extends Delayed>

指定者:

offer 在接口中 Queue<E extends Delayed>

参数:

e - the element to add

返回:

true

抛出:

NullPointerException - if the specified element is null

put

public void put(E e)

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

指定者:

put 在接口中 BlockingQueue<E extends Delayed>

参数:

e - the element to add

抛出:

NullPointerException - if the specified element is null

offer

public 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.

指定者:

offer 在接口中 BlockingQueue<E extends Delayed>

参数:

e - the element to add

timeout - This parameter is ignored as the method never blocks

unit - This parameter is ignored as the method never blocks

返回:

true

抛出:

NullPointerException - if the specified element is null

poll

public E poll()

Retrieves and removes the head of this queue, or returns null if this queue has no elements with an expired delay.

指定者:

poll 在接口中 Queue<E extends Delayed>

返回:

the head of this queue, or null if this queue has no elements with an expired delay

take

public 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.

指定者:

take 在接口中 BlockingQueue<E extends Delayed>

返回:

the head of this queue

抛出:

InterruptedException - if interrupted while waiting

poll

public 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.

指定者:

poll 在接口中 BlockingQueue<E extends Delayed>

参数:

timeout - how long to wait before giving up, in units of unit

unit - a TimeUnit determining how to interpret the timeout parameter

返回:

the head of this queue, or null if the specified waiting time elapses before an element with an expired delay becomes available

抛出:

InterruptedException - if interrupted while waiting

peek

public 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.

指定者:

peek 在接口中 Queue<E extends Delayed>

返回:

the head of this queue, or null if this queue is empty

size

public int size()

从接口复制的说明: Collection

Returns the number of elements in this collection. If this collection contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.

指定者:

size 在接口中 Collection<E extends Delayed>

指定者:

size 在类中 AbstractCollection<E extends Delayed>

返回:

the number of elements in this collection

drainTo

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

从接口复制的说明: 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.

指定者:

drainTo 在接口中 BlockingQueue<E extends Delayed>

参数:

c - the collection to transfer elements into

返回:

the number of elements transferred

抛出:

UnsupportedOperationException - if addition of elements is not supported by the specified collection

ClassCastException - if the class of an element of this queue prevents it from being added to the specified collection

NullPointerException - if the specified collection is null

IllegalArgumentException - if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collection

drainTo

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

从接口复制的说明: 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.

指定者:

drainTo 在接口中 BlockingQueue<E extends Delayed>

参数:

c - the collection to transfer elements into

maxElements - the maximum number of elements to transfer

返回:

the number of elements transferred

抛出:

UnsupportedOperationException - if addition of elements is not supported by the specified collection

ClassCastException - if the class of an element of this queue prevents it from being added to the specified collection

NullPointerException - if the specified collection is null

IllegalArgumentException - if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collection

clear

public 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.

指定者:

clear 在接口中 Collection<E extends Delayed>

覆盖:

clear 在类中 AbstractQueue<E extends Delayed>

remainingCapacity

public int remainingCapacity()

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

指定者:

remainingCapacity 在接口中 BlockingQueue<E extends Delayed>

返回:

Integer.MAX_VALUE

toArray

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. (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.

指定者:

toArray 在接口中 Collection<E extends Delayed>

覆盖:

toArray 在类中 AbstractCollection<E extends Delayed>

返回:

an array containing all of the elements in this queue

toArray

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().

指定者:

toArray 在接口中 Collection<E extends Delayed>

覆盖:

toArray 在类中 AbstractCollection<E extends Delayed>

类型参数:

T - the runtime type of the array to contain the collection

参数:

a - 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 purpose

返回:

an array containing all of the elements in this queue

抛出:

ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this queue

NullPointerException - if the specified array is null

remove

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.

指定者:

remove 在接口中 BlockingQueue<E extends Delayed>

指定者:

remove 在接口中 Collection<E extends Delayed>

覆盖:

remove 在类中 AbstractCollection<E extends Delayed>

参数:

o - element to be removed from this collection, if present

返回:

true if an element was removed as a result of this call

iterator

public 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.

指定者:

iterator 在接口中 Collection<E extends Delayed>

指定者:

iterator 在接口中 Iterable<E extends Delayed>

指定者:

iterator 在类中 AbstractCollection<E extends Delayed>

返回:

an iterator over the elements in this queue