E
- the type of elements held in this collectionpublic class LinkedTransferQueue<E> extends AbstractQueue<E> implements TransferQueue<E>, Serializable
An unbounded TransferQueue
based on linked nodes. This queue orders elements FIFO (first-in-first-out) with respect to any given producer. The head of the queue is that element that has been on the queue the longest time for some producer. The tail of the queue is that element that has been on the queue the shortest time for some producer.
Beware that, unlike in most collections, the size
method is NOT a constant-time operation. Because of the asynchronous nature of these queues, determining the current number of elements requires a traversal of the elements, and so may report inaccurate results if this collection is modified during traversal. Additionally, the bulk operations addAll
, removeAll
, retainAll
, containsAll
, equals
, and toArray
are not guaranteed to be performed atomically. For example, an iterator operating concurrently with an addAll
operation might view only some of the added elements.
This class and its iterator implement all of the optional methods of the Collection
and Iterator
interfaces.
Memory consistency effects: As with other concurrent collections, actions in a thread prior to placing an object into a LinkedTransferQueue
happen-before actions subsequent to the access or removal of that element from the LinkedTransferQueue
in another thread.
This class is a member of the Java Collections Framework.
public LinkedTransferQueue()
Creates an initially empty LinkedTransferQueue
.
public LinkedTransferQueue(Collection<? extends E> c)
Creates a LinkedTransferQueue
initially containing the elements of the given collection, added in traversal order of the collection's iterator.
c
- the collection of elements to initially containNullPointerException
- if the specified collection or any of its elements are nullpublic Spliterator<E> spliterator()
Returns a Spliterator
over the elements in this queue.
The returned spliterator is weakly consistent.
The Spliterator
reports Spliterator.CONCURRENT
, Spliterator.ORDERED
, and Spliterator.NONNULL
.
spliterator
in interface Iterable<E>
spliterator
in interface Collection<E>
Spliterator
implements trySplit
to permit limited parallelism.Spliterator
over the elements in this queuepublic void put(E e)
Inserts the specified element at the tail of this queue. As the queue is unbounded, this method will never block.
put
in interface BlockingQueue<E>
e
- the element to addNullPointerException
- if the specified element is nullpublic boolean offer(E e, long timeout, TimeUnit unit)
Inserts the specified element at the tail of this queue. As the queue is unbounded, this method will never block or return false
.
offer
in interface BlockingQueue<E>
e
- the element to addtimeout
- how long to wait before giving up, in units of unit
unit
- a TimeUnit
determining how to interpret the timeout
parametertrue
(as specified by BlockingQueue.offer
)NullPointerException
- if the specified element is nullpublic boolean offer(E e)
Inserts the specified element at the tail of this queue. As the queue is unbounded, this method will never return false
.
offer
in interface BlockingQueue<E>
offer
in interface Queue<E>
e
- the element to addtrue
(as specified by Queue.offer(E)
)NullPointerException
- if the specified element is nullpublic boolean add(E e)
Inserts the specified element at the tail of this queue. As the queue is unbounded, this method will never throw IllegalStateException
or return false
.
add
in interface Collection<E>
add
in interface BlockingQueue<E>
add
in interface Queue<E>
add
in class AbstractQueue<E>
e
- the element to addtrue
(as specified by Collection.add(E)
)NullPointerException
- if the specified element is nullpublic 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.
tryTransfer
in interface TransferQueue<E>
e
- the element to transfertrue
if the element was transferred, else false
NullPointerException
- if the specified element is nullpublic 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 take()
or timed poll
), else inserts the specified element at the tail of this queue and waits until the element is received by a consumer.
transfer
in interface TransferQueue<E>
e
- the element to transferNullPointerException
- if the specified element is nullInterruptedException
- if interrupted while waiting, in which case the element is not left enqueuedpublic 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 take()
or timed poll
), else inserts the specified element at the tail of this queue and waits until the element is received by a consumer, returning false
if the specified wait time elapses before the element can be transferred.
tryTransfer
in interface TransferQueue<E>
e
- the element to transfertimeout
- how long to wait before giving up, in units of unit
unit
- a TimeUnit
determining how to interpret the timeout
parametertrue
if successful, or false
if the specified waiting time elapses before completion, in which case the element is not left enqueuedNullPointerException
- if the specified element is nullInterruptedException
- if interrupted while waiting, in which case the element is not left enqueuedpublic E take() throws InterruptedException
Description copied from interface: BlockingQueue
Retrieves and removes the head of this queue, waiting if necessary until an element becomes available.
take
in interface BlockingQueue<E>
InterruptedException
- if interrupted while waitingpublic E poll(long timeout, TimeUnit unit) throws InterruptedException
Description copied from interface: BlockingQueue
Retrieves and removes the head of this queue, waiting up to the specified wait time if necessary for an element to become available.
poll
in interface BlockingQueue<E>
timeout
- how long to wait before giving up, in units of unit
unit
- a TimeUnit
determining how to interpret the timeout
parameternull
if the specified waiting time elapses before an element is availableInterruptedException
- if interrupted while waitingpublic E poll()
Description copied from interface: Queue
Retrieves and removes the head of this queue, or returns null
if this queue is empty.
poll
in interface Queue<E>
null
if this queue is emptypublic int drainTo(Collection<? super E> c)
Description copied from interface: 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.
drainTo
in interface BlockingQueue<E>
c
- the collection to transfer elements intoNullPointerException
- if the specified collection is nullIllegalArgumentException
- if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collectionpublic int drainTo(Collection<? super E> c, int maxElements)
Description copied from interface: 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.
drainTo
in interface BlockingQueue<E>
c
- the collection to transfer elements intomaxElements
- the maximum number of elements to transferNullPointerException
- if the specified collection is nullIllegalArgumentException
- if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collectionpublic Iterator<E> iterator()
Returns an iterator over the elements in this queue in proper sequence. The elements will be returned in order from first (head) to last (tail).
The returned iterator is weakly consistent.
iterator
in interface Iterable<E>
iterator
in interface Collection<E>
iterator
in class AbstractCollection<E>
public E peek()
Description copied from interface: Queue
Retrieves, but does not remove, the head of this queue, or returns null
if this queue is empty.
peek
in interface Queue<E>
null
if this queue is emptypublic boolean isEmpty()
Returns true
if this queue contains no elements.
isEmpty
in interface Collection<E>
isEmpty
in class AbstractCollection<E>
true
if this queue contains no elementspublic boolean hasWaitingConsumer()
Description copied from interface: TransferQueue
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.
hasWaitingConsumer
in interface TransferQueue<E>
true
if there is at least one waiting consumerpublic int size()
Returns the number of elements in this queue. If this queue contains more than Integer.MAX_VALUE
elements, returns Integer.MAX_VALUE
.
Beware that, unlike in most collections, this method is NOT a constant-time operation. Because of the asynchronous nature of these queues, determining the current number of elements requires an O(n) traversal.
size
in interface Collection<E>
size
in class AbstractCollection<E>
public int getWaitingConsumerCount()
Description copied from interface: TransferQueue
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 TransferQueue.hasWaitingConsumer()
.
getWaitingConsumerCount
in interface TransferQueue<E>
public boolean remove(Object o)
Removes a single instance of the specified element from this queue, if it is present. More formally, removes an element e
such that o.equals(e)
, if this queue contains one or more such elements. Returns true
if this queue contained the specified element (or equivalently, if this queue changed as a result of the call).
remove
in interface Collection<E>
remove
in interface BlockingQueue<E>
remove
in class AbstractCollection<E>
o
- element to be removed from this queue, if presenttrue
if this queue changed as a result of the callpublic boolean contains(Object o)
Returns true
if this queue contains the specified element. More formally, returns true
if and only if this queue contains at least one element e
such that o.equals(e)
.
contains
in interface Collection<E>
contains
in interface BlockingQueue<E>
contains
in class AbstractCollection<E>
o
- object to be checked for containment in this queuetrue
if this queue contains the specified elementpublic int remainingCapacity()
Always returns Integer.MAX_VALUE
because a LinkedTransferQueue
is not capacity constrained.
remainingCapacity
in interface BlockingQueue<E>
Integer.MAX_VALUE
(as specified by BlockingQueue.remainingCapacity
)
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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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