程序包 java.util.concurrent

类 SynchronousQueue<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractQueue<E>

java.util.concurrent.SynchronousQueue<E>

类型参数:

E - the type of elements held in this collection

所有已实现的接口:

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

public class SynchronousQueue<E>
extends AbstractQueue<E>
implements BlockingQueue<E>, Serializable

A BlockingQueue in which each insert operation must wait for a corresponding remove operation by another thread, and vice versa. A synchronous queue does not have any internal capacity, not even a capacity of one. You cannot peek at a synchronous queue because an element is only present when you try to remove it; you cannot insert an element (using any method) unless another thread is trying to remove it; you cannot iterate as there is nothing to iterate. The head of the queue is the element that the first queued inserting thread is trying to add to the queue; if there is no such queued thread then no element is available for removal and poll() will return null. For purposes of other Collection methods (for example contains), a SynchronousQueue acts as an empty collection. This queue does not permit null elements.

Synchronous queues are similar to rendezvous channels used in CSP and Ada. They are well suited for handoff designs, in which an object running in one thread must sync up with an object running in another thread in order to hand it some information, event, or task.

This class supports an optional fairness policy for ordering waiting producer and consumer threads. By default, this ordering is not guaranteed. However, a queue constructed with fairness set to true grants threads access in FIFO order.

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.

从以下版本开始:

1.5

另请参阅:

序列化表格

构造器概要

构造器

构造器	说明
SynchronousQueue()	Creates a SynchronousQueue with nonfair access policy.
SynchronousQueue(boolean fair)	Creates a SynchronousQueue with the specified fairness policy.

方法概要

限定符和类型	方法	说明
void	clear()	Does nothing.
boolean	contains(Object o)	Always returns false.
boolean	containsAll(Collection<?> c)	Returns false unless the given collection is empty.
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.
boolean	isEmpty()	Always returns true.
Iterator<E>	iterator()	Returns an empty iterator in which hasNext always returns false.
boolean	offer(E e)	Inserts the specified element into this queue, if another thread is waiting to receive it.
boolean	offer(E e, long timeout, TimeUnit unit)	Inserts the specified element into this queue, waiting if necessary up to the specified wait time for another thread to receive it.
E	peek()	Always returns null.
E	poll()	Retrieves and removes the head of this queue, if another thread is currently making an element available.
E	poll(long timeout, TimeUnit unit)	Retrieves and removes the head of this queue, waiting if necessary up to the specified wait time, for another thread to insert it.
void	put(E e)	Adds the specified element to this queue, waiting if necessary for another thread to receive it.
int	remainingCapacity()	Always returns zero.
boolean	remove(Object o)	Always returns false.
boolean	removeAll(Collection<?> c)	Always returns false.
boolean	retainAll(Collection<?> c)	Always returns false.
int	size()	Always returns zero.
Spliterator<E>	spliterator()	Returns an empty spliterator in which calls to Spliterator.trySplit() always return null.
E	take()	Retrieves and removes the head of this queue, waiting if necessary for another thread to insert it.
Object[]	toArray()	Returns a zero-length array.
<T> T[]	toArray(T[] a)	Sets the zeroeth element of the specified array to null (if the array has non-zero length) and returns it.

从类继承的方法 java.util.AbstractCollection

toString

从类继承的方法 java.util.AbstractQueue

add, addAll, element, remove

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

add

从接口继承的方法 java.util.Collection

addAll, equals, hashCode, parallelStream, removeIf, 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

SynchronousQueue

public SynchronousQueue()

Creates a SynchronousQueue with nonfair access policy.

SynchronousQueue

public SynchronousQueue(boolean fair)

Creates a SynchronousQueue with the specified fairness policy.

参数:

fair - if true, waiting threads contend in FIFO order for access; otherwise the order is unspecified.

方法详细资料

put

public void put(E e)
         throws InterruptedException

Adds the specified element to this queue, waiting if necessary for another thread to receive it.

指定者:

put 在接口中 BlockingQueue<E>

参数:

e - the element to add

抛出:

InterruptedException - if interrupted while waiting

NullPointerException - if the specified element is null

offer

public boolean offer(E e,
                     long timeout,
                     TimeUnit unit)
              throws InterruptedException

Inserts the specified element into this queue, waiting if necessary up to the specified wait time for another thread to receive it.

指定者:

offer 在接口中 BlockingQueue<E>

参数:

e - the element to add

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

unit - a TimeUnit determining how to interpret the timeout parameter

返回:

true if successful, or false if the specified waiting time elapses before a consumer appears

抛出:

InterruptedException - if interrupted while waiting

NullPointerException - if the specified element is null

offer

public boolean offer(E e)

Inserts the specified element into this queue, if another thread is waiting to receive it.

指定者:

offer 在接口中 BlockingQueue<E>

指定者:

offer 在接口中 Queue<E>

参数:

e - the element to add

返回:

true if the element was added to this queue, else false

抛出:

NullPointerException - if the specified element is null

take

public E take()
       throws InterruptedException

Retrieves and removes the head of this queue, waiting if necessary for another thread to insert it.

指定者:

take 在接口中 BlockingQueue<E>

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 up to the specified wait time, for another thread to insert it.

指定者:

poll 在接口中 BlockingQueue<E>

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 is present

抛出:

InterruptedException - if interrupted while waiting

poll

public E poll()

Retrieves and removes the head of this queue, if another thread is currently making an element available.

指定者:

poll 在接口中 Queue<E>

返回:

the head of this queue, or null if no element is available

isEmpty

public boolean isEmpty()

Always returns true. A SynchronousQueue has no internal capacity.

指定者:

isEmpty 在接口中 Collection<E>

覆盖:

isEmpty 在类中 AbstractCollection<E>

返回:

true

size

public int size()

Always returns zero. A SynchronousQueue has no internal capacity.

指定者:

size 在接口中 Collection<E>

指定者:

size 在类中 AbstractCollection<E>

返回:

zero

remainingCapacity

public int remainingCapacity()

Always returns zero. A SynchronousQueue has no internal capacity.

指定者:

remainingCapacity 在接口中 BlockingQueue<E>

返回:

zero

clear

public void clear()

Does nothing. A SynchronousQueue has no internal capacity.

指定者:

clear 在接口中 Collection<E>

覆盖:

clear 在类中 AbstractQueue<E>

contains

public boolean contains(Object o)

Always returns false. A SynchronousQueue has no internal capacity.

指定者:

contains 在接口中 BlockingQueue<E>

指定者:

contains 在接口中 Collection<E>

覆盖:

contains 在类中 AbstractCollection<E>

参数:

o - the element

返回:

false

remove

public boolean remove(Object o)

Always returns false. A SynchronousQueue has no internal capacity.

指定者:

remove 在接口中 BlockingQueue<E>

指定者:

remove 在接口中 Collection<E>

覆盖:

remove 在类中 AbstractCollection<E>

参数:

o - the element to remove

返回:

false

containsAll

public boolean containsAll(Collection<?> c)

Returns false unless the given collection is empty. A SynchronousQueue has no internal capacity.

指定者:

containsAll 在接口中 Collection<E>

覆盖:

containsAll 在类中 AbstractCollection<E>

参数:

c - the collection

返回:

false unless given collection is empty

另请参阅:

AbstractCollection.contains(Object)

removeAll

public boolean removeAll(Collection<?> c)

Always returns false. A SynchronousQueue has no internal capacity.

指定者:

removeAll 在接口中 Collection<E>

覆盖:

removeAll 在类中 AbstractCollection<E>

参数:

c - the collection

返回:

false

另请参阅:

AbstractCollection.remove(Object), AbstractCollection.contains(Object)

retainAll

public boolean retainAll(Collection<?> c)

Always returns false. A SynchronousQueue has no internal capacity.

指定者:

retainAll 在接口中 Collection<E>

覆盖:

retainAll 在类中 AbstractCollection<E>

参数:

c - the collection

返回:

false

另请参阅:

AbstractCollection.remove(Object), AbstractCollection.contains(Object)

peek

public E peek()

Always returns null. A SynchronousQueue does not return elements unless actively waited on.

指定者:

peek 在接口中 Queue<E>

返回:

null

iterator

public Iterator<E> iterator()

Returns an empty iterator in which hasNext always returns false.

指定者:

iterator 在接口中 Collection<E>

指定者:

iterator 在接口中 Iterable<E>

指定者:

iterator 在类中 AbstractCollection<E>

返回:

an empty iterator

spliterator

public Spliterator<E> spliterator()

Returns an empty spliterator in which calls to Spliterator.trySplit() always return null.

指定者:

spliterator 在接口中 Collection<E>

指定者:

spliterator 在接口中 Iterable<E>

返回:

an empty spliterator

从以下版本开始:

1.8

toArray

public Object[] toArray()

Returns a zero-length array.

指定者:

toArray 在接口中 Collection<E>

覆盖:

toArray 在类中 AbstractCollection<E>

返回:

a zero-length array

toArray

public <T> T[] toArray(T[] a)

Sets the zeroeth element of the specified array to null (if the array has non-zero length) and returns it.

指定者:

toArray 在接口中 Collection<E>

覆盖:

toArray 在类中 AbstractCollection<E>

类型参数:

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

参数:

a - the array

返回:

the specified array

抛出:

NullPointerException - if the specified array is null

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>

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>

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