E
- the type of elements held in this collectionpublic class LinkedTransferQueue<E> extends AbstractQueue<E> implements TransferQueue<E>, Serializable
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.
Constructor and Description |
---|
LinkedTransferQueue()
Creates an initially empty
LinkedTransferQueue . |
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. |
Modifier and Type | Method and Description |
---|---|
boolean |
add(E e)
Inserts the specified element at the tail of this queue.
|
boolean |
contains(Object o)
Returns
true if this queue contains the specified element. |
int |
drainTo(Collection<? super E> c)
Removes all available elements from this queue and adds them
to the given collection.
|
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.
|
int |
getWaitingConsumerCount()
Returns an estimate of the number of consumers waiting to
receive elements via
BlockingQueue.take() or timed
poll . |
boolean |
hasWaitingConsumer()
Returns
true if there is at least one consumer waiting
to receive an element via BlockingQueue.take() or
timed poll . |
boolean |
isEmpty()
Returns
true if this queue contains no elements. |
Iterator<E> |
iterator()
Returns an iterator over the elements in this queue in proper sequence.
|
boolean |
offer(E e)
Inserts the specified element at the tail of this queue.
|
boolean |
offer(E e,
long timeout,
TimeUnit unit)
Inserts the specified element at the tail of this queue.
|
E |
peek()
Retrieves, but does not remove, the head of this queue,
or returns
null if this queue is empty. |
E |
poll()
Retrieves and removes the head of this queue,
or returns
null if this queue is empty. |
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.
|
void |
put(E e)
Inserts the specified element at the tail of this queue.
|
int |
remainingCapacity()
Always returns
Integer.MAX_VALUE because a
LinkedTransferQueue is not capacity constrained. |
boolean |
remove(Object o)
Removes a single instance of the specified element from this queue,
if it is present.
|
int |
size()
Returns the number of elements in this queue.
|
Spliterator<E> |
spliterator()
Returns a
Spliterator over the elements in this queue. |
E |
take()
Retrieves and removes the head of this queue, waiting if necessary
until an element becomes available.
|
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.
|
addAll, clear, element, remove
containsAll, removeAll, retainAll, toArray, toArray, toString
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
addAll, clear, containsAll, equals, hashCode, parallelStream, removeAll, removeIf, retainAll, stream, toArray, toArray
public LinkedTransferQueue()
LinkedTransferQueue
.public LinkedTransferQueue(Collection<? extends E> c)
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()
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)
put
in interface BlockingQueue<E>
e
- the element to addNullPointerException
- if the specified element is nullpublic boolean offer(E e, long timeout, TimeUnit unit)
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)
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)
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)
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
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
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
BlockingQueue
take
in interface BlockingQueue<E>
InterruptedException
- if interrupted while waitingpublic E poll(long timeout, TimeUnit unit) throws InterruptedException
BlockingQueue
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()
Queue
null
if this queue is empty.public int drainTo(Collection<? super E> c)
BlockingQueue
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)
BlockingQueue
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()
The returned iterator is weakly consistent.
iterator
in interface Iterable<E>
iterator
in interface Collection<E>
iterator
in class AbstractCollection<E>
public E peek()
Queue
null
if this queue is empty.public boolean isEmpty()
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()
TransferQueue
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()
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()
TransferQueue
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)
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)
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()
Integer.MAX_VALUE
because a
LinkedTransferQueue
is not capacity constrained.remainingCapacity
in interface BlockingQueue<E>
Integer.MAX_VALUE
(as specified by
BlockingQueue.remainingCapacity
) Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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