E - the type of elements held in this collectionpublic class ArrayBlockingQueue<E> extends AbstractQueue<E> implements BlockingQueue<E>, Serializable
This is a classic "bounded buffer", in which a
fixed-sized array holds elements inserted by producers and
extracted by consumers. Once created, the capacity cannot be
changed. Attempts to put an element into a full queue
will result in the operation blocking; attempts to take an
element from an empty queue will similarly block.
This class supports an optional fairness policy for ordering
waiting producer and consumer threads. By default, this ordering
is not guaranteed. However, a queue constructed with fairness set
to true grants threads access in FIFO order. Fairness
generally decreases throughput but reduces variability and avoids
starvation.
This class and its iterator implement all of the
optional methods of the Collection and Iterator interfaces.
This class is a member of the Java Collections Framework.
| Constructor and Description |
|---|
ArrayBlockingQueue(int capacity)
Creates an
ArrayBlockingQueue with the given (fixed)
capacity and default access policy. |
ArrayBlockingQueue(int capacity,
boolean fair)
Creates an
ArrayBlockingQueue with the given (fixed)
capacity and the specified access policy. |
ArrayBlockingQueue(int capacity,
boolean fair,
Collection<? extends E> c)
Creates an
ArrayBlockingQueue with the given (fixed)
capacity, the specified access policy and 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 if it is
possible to do so immediately without exceeding the queue's capacity,
returning
true upon success and throwing an
IllegalStateException if this queue is full. |
void |
clear()
Atomically removes all of the elements from 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.
|
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 if it is
possible to do so immediately without exceeding the queue's capacity,
returning
true upon success and false if this queue
is full. |
boolean |
offer(E e,
long timeout,
TimeUnit unit)
Inserts the specified element at the tail of this queue, waiting
up to the specified wait time for space to become available if
the queue is full.
|
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, waiting
for space to become available if the queue is full.
|
int |
remainingCapacity()
Returns the number of additional elements that this queue can ideally
(in the absence of memory or resource constraints) accept without
blocking.
|
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.
|
Object[] |
toArray()
Returns an array containing all of the elements in this queue, in
proper sequence.
|
<T> T[] |
toArray(T[] a)
Returns an array containing all of the elements in this queue, in
proper sequence; the runtime type of the returned array is that of
the specified array.
|
String |
toString()
Returns a string representation of this collection.
|
addAll, element, removecontainsAll, isEmpty, removeAll, retainAllclone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, waitaddAll, containsAll, equals, hashCode, isEmpty, parallelStream, removeAll, removeIf, retainAll, streampublic ArrayBlockingQueue(int capacity)
ArrayBlockingQueue with the given (fixed)
capacity and default access policy.capacity - the capacity of this queueIllegalArgumentException - if capacity < 1public ArrayBlockingQueue(int capacity,
boolean fair)
ArrayBlockingQueue with the given (fixed)
capacity and the specified access policy.capacity - the capacity of this queuefair - if true then queue accesses for threads blocked
on insertion or removal, are processed in FIFO order;
if false the access order is unspecified.IllegalArgumentException - if capacity < 1public ArrayBlockingQueue(int capacity,
boolean fair,
Collection<? extends E> c)
ArrayBlockingQueue with the given (fixed)
capacity, the specified access policy and initially containing the
elements of the given collection,
added in traversal order of the collection's iterator.capacity - the capacity of this queuefair - if true then queue accesses for threads blocked
on insertion or removal, are processed in FIFO order;
if false the access order is unspecified.c - the collection of elements to initially containIllegalArgumentException - if capacity is less than
c.size(), or less than 1.NullPointerException - if the specified collection or any
of its elements are nullpublic boolean add(E e)
true upon success and throwing an
IllegalStateException if this queue is full.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))IllegalStateException - if this queue is fullNullPointerException - if the specified element is nullpublic boolean offer(E e)
true upon success and false if this queue
is full. This method is generally preferable to method add(E),
which can fail to insert an element only by throwing an exception.offer in interface BlockingQueue<E>offer in interface Queue<E>e - the element to addtrue if the element was added to this queue, else
falseNullPointerException - if the specified element is nullpublic void put(E e) throws InterruptedException
put in interface BlockingQueue<E>e - the element to addInterruptedException - if interrupted while waitingNullPointerException - if the specified element is nullpublic boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException
offer in interface BlockingQueue<E>e - the element to addtimeout - how long to wait before giving up, in units of
unitunit - a TimeUnit determining how to interpret the
timeout parametertrue if successful, or false if
the specified waiting time elapses before space is availableInterruptedException - if interrupted while waitingNullPointerException - if the specified element is nullpublic E poll()
Queuenull if this queue is empty.public E take() throws InterruptedException
BlockingQueuetake in interface BlockingQueue<E>InterruptedException - if interrupted while waitingpublic E poll(long timeout, TimeUnit unit) throws InterruptedException
BlockingQueuepoll in interface BlockingQueue<E>timeout - how long to wait before giving up, in units of
unitunit - 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 peek()
Queuenull if this queue is empty.public int size()
size in interface Collection<E>size in class AbstractCollection<E>public int remainingCapacity()
size of this queue.
Note that you cannot always tell if an attempt to insert
an element will succeed by inspecting remainingCapacity
because it may be the case that another thread is about to
insert or remove an element.
remainingCapacity in interface BlockingQueue<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).
Removal of interior elements in circular array based queues is an intrinsically slow and disruptive operation, so should be undertaken only in exceptional circumstances, ideally only when the queue is known not to be accessible by other threads.
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 Object[] toArray()
The returned array will be "safe" in that no references to it are maintained by this queue. (In other words, this method must allocate a new array). The caller is thus free to modify the returned array.
This method acts as bridge between array-based and collection-based APIs.
toArray in interface Collection<E>toArray in class AbstractCollection<E>public <T> T[] toArray(T[] a)
If this queue fits in the specified array with room to spare
(i.e., the array has more elements than this queue), the element in
the array immediately following the end of the queue is set to
null.
Like the toArray() method, this method acts as bridge between
array-based and collection-based APIs. Further, this method allows
precise control over the runtime type of the output array, and may,
under certain circumstances, be used to save allocation costs.
Suppose x is a queue known to contain only strings.
The following code can be used to dump the queue into a newly
allocated array of String:
String[] y = x.toArray(new String[0]);
Note that toArray(new Object[0]) is identical in function to
toArray().toArray in interface Collection<E>toArray in class AbstractCollection<E>T - the runtime type of the array to contain the collectiona - the array into which the elements of the queue are to
be stored, if it is big enough; otherwise, a new array of the
same runtime type is allocated for this purposeArrayStoreException - if the runtime type of the specified array
is not a supertype of the runtime type of every element in
this queueNullPointerException - if the specified array is nullpublic String toString()
AbstractCollectionString.valueOf(Object).toString in class AbstractCollection<E>public void clear()
clear in interface Collection<E>clear in class AbstractQueue<E>public int drainTo(Collection<? super E> c)
BlockingQueuec 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 intoUnsupportedOperationException - if addition of elements
is not supported by the specified collectionClassCastException - if the class of an element of this queue
prevents it from being added to the specified collectionNullPointerException - 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)
BlockingQueuec 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 transferUnsupportedOperationException - if addition of elements
is not supported by the specified collectionClassCastException - if the class of an element of this queue
prevents it from being added to the specified collectionNullPointerException - 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 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 queue 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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