com.alibaba.druid.util

接口 TransferQueue<E>

类型参数:

E - the type of elements held in this collection

所有超级接口:

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

public interface TransferQueue<E>
extends BlockingQueue<E>

A BlockingQueue in which producers may wait for consumers to receive elements. A TransferQueue may be useful for example in message passing applications in which producers sometimes (using method transfer(E)) await receipt of elements by consumers invoking take or poll, while at other times enqueue elements (via method put) without waiting for receipt. Non-blocking and time-out versions of tryTransfer are also available. A TransferQueue may also be queried, via hasWaitingConsumer(), whether there are any threads waiting for items, which is a converse analogy to a peek operation.

Like other blocking queues, a TransferQueue may be capacity bounded. If so, an attempted transfer operation may initially block waiting for available space, and/or subsequently block waiting for reception by a consumer. Note that in a queue with zero capacity, such as SynchronousQueue, put and transfer are effectively synonymous.

This interface is a member of the Java Collections Framework.

从以下版本开始:

1.7

作者:

Doug Lea

方法概要

方法

限定符和类型	方法和说明
int	getWaitingConsumerCount() Returns an estimate of the number of consumers waiting to receive elements via BlockingQueue.take() or timed poll.
boolean	hasWaitingConsumer() Returns true if there is at least one consumer waiting to receive an element via BlockingQueue.take() or timed poll.
void	transfer(E e) Transfers the element to a consumer, waiting if necessary to do so.
boolean	tryTransfer(E e) Transfers the element to a waiting consumer immediately, if possible.
boolean	tryTransfer(E e, long timeout, TimeUnit unit) Transfers the element to a consumer if it is possible to do so before the timeout elapses.

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

add, contains, drainTo, drainTo, offer, offer, poll, put, remainingCapacity, remove, take

从接口继承的方法 java.util.Queue

element, peek, poll, remove

从接口继承的方法 java.util.Collection

addAll, clear, containsAll, equals, hashCode, isEmpty, iterator, removeAll, retainAll, size, toArray, toArray

方法详细资料

tryTransfer

boolean tryTransfer(E e)

Transfers the element to a waiting consumer immediately, if possible.

More precisely, transfers the specified element immediately if there exists a consumer already waiting to receive it (in BlockingQueue.take() or timed poll), otherwise returning false without enqueuing the element.

参数:

e - the element to transfer

返回:

true if the element was transferred, else false

抛出:

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

NullPointerException - if the specified element is null

IllegalArgumentException - if some property of the specified element prevents it from being added to this queue

transfer

void transfer(E e)
              throws InterruptedException

Transfers the element to a consumer, waiting if necessary to do so.

More precisely, transfers the specified element immediately if there exists a consumer already waiting to receive it (in BlockingQueue.take() or timed poll), else waits until the element is received by a consumer.

参数:

e - the element to transfer

抛出:

InterruptedException - if interrupted while waiting, in which case the element is not left enqueued

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

NullPointerException - if the specified element is null

IllegalArgumentException - if some property of the specified element prevents it from being added to this queue

tryTransfer

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

Transfers the element to a consumer if it is possible to do so before the timeout elapses.

More precisely, transfers the specified element immediately if there exists a consumer already waiting to receive it (in BlockingQueue.take() or timed poll), else waits until the element is received by a consumer, returning false if the specified wait time elapses before the element can be transferred.

参数:

e - the element to transfer

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 completion, in which case the element is not left enqueued

抛出:

InterruptedException - if interrupted while waiting, in which case the element is not left enqueued

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

NullPointerException - if the specified element is null

IllegalArgumentException - if some property of the specified element prevents it from being added to this queue

hasWaitingConsumer

boolean hasWaitingConsumer()

Returns true if there is at least one consumer waiting to receive an element via BlockingQueue.take() or timed poll. The return value represents a momentary state of affairs.

返回:

true if there is at least one waiting consumer

getWaitingConsumerCount

int getWaitingConsumerCount()

Returns an estimate of the number of consumers waiting to receive elements via BlockingQueue.take() or timed poll. The return value is an approximation of a momentary state of affairs, that may be inaccurate if consumers have completed or given up waiting. The value may be useful for monitoring and heuristics, but not for synchronization control. Implementations of this method are likely to be noticeably slower than those for hasWaitingConsumer().

返回:

the number of consumers waiting to receive elements