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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