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Added in API level 21

Summary: Methods | Inherited Methods | [Expand All]

TransferQueue

public interface TransferQueue
implements BlockingQueue<E>

java.util.concurrent.TransferQueue<E>

Known Indirect Subclasses

LinkedTransferQueue<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.

Summary

Public methods
`abstract int`	`getWaitingConsumerCount()` Returns an estimate of the number of consumers waiting to receive elements via `take()` or timed `poll`.
`abstract boolean`	`hasWaitingConsumer()` Returns `true` if there is at least one consumer waiting to receive an element via `take()` or timed `poll`.
`abstract void`	`transfer(E e)` Transfers the element to a consumer, waiting if necessary to do so.
`abstract boolean`	`tryTransfer(E e)` Transfers the element to a waiting consumer immediately, if possible.
`abstract 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.

Inherited methods

From interface


  
    java.util.concurrent.BlockingQueue

`abstract boolean`	`add(E e)` Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning `true` upon success and throwing an `IllegalStateException` if no space is currently available.
`abstract boolean`	`contains(Object o)` Returns `true` if this queue contains the specified element.
`abstract int`	`drainTo(Collection<? super E> c)` Removes all available elements from this queue and adds them to the given collection.
`abstract 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.
`abstract boolean`	`offer(E e)` Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning `true` upon success and `false` if no space is currently available.
`abstract boolean`	`offer(E e, long timeout, TimeUnit unit)` Inserts the specified element into this queue, waiting up to the specified wait time if necessary for space to become available.
`abstract E`	`poll(long timeout, TimeUnit unit)` Retrieves and removes the head of this queue, waiting up to the specified wait time if necessary for an element to become available.
`abstract void`	`put(E e)` Inserts the specified element into this queue, waiting if necessary for space to become available.
`abstract int`	`remainingCapacity()` Returns the number of additional elements that this queue can ideally (in the absence of memory or resource constraints) accept without blocking, or `Integer.MAX_VALUE` if there is no intrinsic limit.
`abstract boolean`	`remove(Object o)` Removes a single instance of the specified element from this queue, if it is present.
`abstract E`	`take()` Retrieves and removes the head of this queue, waiting if necessary until an element becomes available.

From interface


  
    java.util.Queue

From interface


  
    java.util.Collection

`abstract boolean`	`add(E e)` Ensures that this collection contains the specified element (optional operation).
`abstract boolean`	`addAll(Collection<? extends E> c)` Adds all of the elements in the specified collection to this collection (optional operation).
`abstract void`	`clear()` Removes all of the elements from this collection (optional operation).
`abstract boolean`	`contains(Object o)` Returns `true` if this collection contains the specified element.
`abstract boolean`	`containsAll(Collection<?> c)` Returns `true` if this collection contains all of the elements in the specified collection.
`abstract boolean`	`equals(Object o)` Compares the specified object with this collection for equality.
`abstract int`	`hashCode()` Returns the hash code value for this collection.
`abstract boolean`	`isEmpty()` Returns `true` if this collection contains no elements.
`abstract Iterator<E>`	`iterator()` Returns an iterator over the elements in this collection.
`default Stream<E>`	`parallelStream()` Returns a possibly parallel `Stream` with this collection as its source.
`abstract boolean`	`remove(Object o)` Removes a single instance of the specified element from this collection, if it is present (optional operation).
`abstract boolean`	`removeAll(Collection<?> c)` Removes all of this collection's elements that are also contained in the specified collection (optional operation).
`default boolean`	`removeIf(Predicate<? super E> filter)` Removes all of the elements of this collection that satisfy the given predicate.
`abstract boolean`	`retainAll(Collection<?> c)` Retains only the elements in this collection that are contained in the specified collection (optional operation).
`abstract int`	`size()` Returns the number of elements in this collection.
`default Spliterator<E>`	`spliterator()` Creates a `Spliterator` over the elements in this collection.
`default Stream<E>`	`stream()` Returns a sequential `Stream` with this collection as its source.
`abstract <T> T[]`	`toArray(T[] a)` Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.
`abstract Object[]`	`toArray()` Returns an array containing all of the elements in this collection.

From interface


  
    java.lang.Iterable

Public methods

getWaitingConsumerCount

Added in API level 21

int getWaitingConsumerCount ()

Returns an estimate of the number of consumers waiting to receive elements via 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
`int`	the number of consumers waiting to receive elements

hasWaitingConsumer

Added in API level 21

boolean hasWaitingConsumer ()

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

Returns
`boolean`	`true` if there is at least one waiting consumer

transfer

Added in API level 21

void transfer (E e)

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

Parameters
`e`	`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

Added in API level 21

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 take() or timed poll), otherwise returning false without enqueuing the element.

Parameters
`e`	`E`: the element to transfer

Returns
`boolean`	`true` if the element was transferred, else `false`

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

tryTransfer

Added in API level 21

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.

More precisely, transfers the specified element immediately if there exists a consumer already waiting to receive it (in 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`	`E`: the element to transfer
`timeout`	`long`: how long to wait before giving up, in units of `unit`
`unit`	`TimeUnit`: a `TimeUnit` determining how to interpret the `timeout` parameter

Returns
`boolean`	`true` if successful, or `false` 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

Interfaces

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Exceptions

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TransferQueue

Summary

Public methods

Inherited methods

Public methods

getWaitingConsumerCount

hasWaitingConsumer

transfer

tryTransfer

tryTransfer