Interface TransferQueue<E>
- Type Parameters:
-
E
- the type of elements held in this queue
- All Superinterfaces:
-
BlockingQueue<E>
,Collection<E>
,Iterable<E>
,Queue<E>
- All Known Implementing Classes:
LinkedTransferQueue
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.
- Since:
- 1.7
Method Summary
Modifier and Type | Method | Description |
---|---|---|
int | getWaitingConsumerCount() | Returns an estimate of the number of consumers waiting to receive elements via |
boolean | hasWaitingConsumer() | Returns |
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. |
Methods declared in interface java.util.concurrent.BlockingQueue
add, contains, drainTo, drainTo, offer, offer, poll, put, remainingCapacity, remove, take
Methods declared in interface java.util.Collection
addAll, clear, containsAll, equals, hashCode, isEmpty, iterator, parallelStream, removeAll, removeIf, retainAll, size, spliterator, stream, toArray, toArray, toArray
Methods declared in interface java.lang.Iterable
forEach
Methods declared in interface java.util.Queue
element, peek, poll, remove
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 timed poll
), otherwise returning false
without enqueuing the element.
- Parameters:
-
e
- the element to transfer - Returns:
-
true
if the element was transferred, elsefalse
- Throws:
-
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.
- Parameters:
-
e
- the element to transfer - Throws:
-
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.
- Parameters:
-
e
- the element to transfer -
timeout
- how long to wait before giving up, in units ofunit
-
unit
- aTimeUnit
determining how to interpret thetimeout
parameter - Returns:
-
true
if successful, orfalse
if the specified waiting time elapses before completion, in which case the element is not left enqueued - Throws:
-
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.
- Returns:
-
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()
.
- Returns:
- the number of consumers waiting to receive elements