Interface TransferQueue<E>
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- Type Parameters:
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E- the type of elements held in this collection
- All Superinterfaces:
- BlockingQueue<E>, Collection<E>, Iterable<E>, Queue<E>
- All Known Implementing Classes:
- LinkedTransferQueue
public interface TransferQueue<E> extends BlockingQueue<E>
ABlockingQueuein which producers may wait for consumers to receive elements. ATransferQueuemay be useful for example in message passing applications in which producers sometimes (using methodtransfer(E)) await receipt of elements by consumers invokingtakeorpoll, while at other times enqueue elements (via methodput) without waiting for receipt. Non-blocking and time-out versions oftryTransferare also available. ATransferQueuemay also be queried, viahasWaitingConsumer(), whether there are any threads waiting for items, which is a converse analogy to apeekoperation.Like other blocking queues, a
TransferQueuemay 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 asSynchronousQueue,putandtransferare effectively synonymous.This interface is a member of the Java Collections Framework.
- Since:
- 1.7
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method and Description intgetWaitingConsumerCount()Returns an estimate of the number of consumers waiting to receive elements viaBlockingQueue.take()or timedpoll.booleanhasWaitingConsumer()Returnstrueif there is at least one consumer waiting to receive an element viaBlockingQueue.take()or timedpoll.voidtransfer(E e)Transfers the element to a consumer, waiting if necessary to do so.booleantryTransfer(E e)Transfers the element to a waiting consumer immediately, if possible.booleantryTransfer(E e, long timeout, TimeUnit unit)Transfers the element to a consumer if it is possible to do so before the timeout elapses.-
Methods inherited from interface java.util.concurrent.BlockingQueue
add, contains, drainTo, drainTo, offer, offer, poll, put, remainingCapacity, remove, take
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Methods inherited from interface java.util.Collection
addAll, clear, containsAll, equals, hashCode, isEmpty, iterator, parallelStream, removeAll, removeIf, retainAll, size, spliterator, stream, toArray, toArray
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Method Detail
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 timedpoll), otherwise returningfalsewithout enqueuing the element.- Parameters:
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e- the element to transfer - Returns:
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trueif the element was transferred, elsefalse - Throws:
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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 timedpoll), else waits until the element is received by a consumer.- Parameters:
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e- the element to transfer - Throws:
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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 timedpoll), else waits until the element is received by a consumer, returningfalseif the specified wait time elapses before the element can be transferred.- Parameters:
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e- the element to transfer -
timeout- how long to wait before giving up, in units ofunit -
unit- aTimeUnitdetermining how to interpret thetimeoutparameter - Returns:
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trueif successful, orfalseif the specified waiting time elapses before completion, in which case the element is not left enqueued - Throws:
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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()
Returnstrueif there is at least one consumer waiting to receive an element viaBlockingQueue.take()or timedpoll. The return value represents a momentary state of affairs.- Returns:
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trueif there is at least one waiting consumer
getWaitingConsumerCount
int getWaitingConsumerCount()
Returns an estimate of the number of consumers waiting to receive elements viaBlockingQueue.take()or timedpoll. 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 forhasWaitingConsumer().- Returns:
- the number of consumers waiting to receive elements
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