- java.lang.Object
-
- java.util.AbstractCollection<E>
-
- java.util.AbstractQueue<E>
-
- java.util.concurrent.ArrayBlockingQueue<E>
-
- Type Parameters:
E
- the type of elements held in this collection
- All Implemented Interfaces:
- Serializable, Iterable<E>, Collection<E>, BlockingQueue<E>, Queue<E>
public class ArrayBlockingQueue<E> extends AbstractQueue<E> implements BlockingQueue<E>, Serializable
A bounded blocking queue backed by an array. This queue orders elements FIFO (first-in-first-out). The head of the queue is that element that has been on the queue the longest time. The tail of the queue is that element that has been on the queue the shortest time. New elements are inserted at the tail of the queue, and the queue retrieval operations obtain elements at the head of the queue.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 totake
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
andIterator
interfaces.This class is a member of the Java Collections Framework.
- Since:
- 1.5
- See Also:
- Serialized Form
-
-
Constructor Summary
Constructors Constructor and Description ArrayBlockingQueue(int capacity)
Creates anArrayBlockingQueue
with the given (fixed) capacity and default access policy.ArrayBlockingQueue(int capacity, boolean fair)
Creates anArrayBlockingQueue
with the given (fixed) capacity and the specified access policy.ArrayBlockingQueue(int capacity, boolean fair, Collection<? extends E> c)
Creates anArrayBlockingQueue
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.
-
Method Summary
Methods 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, returningtrue
upon success and throwing anIllegalStateException
if this queue is full.void
clear()
Atomically removes all of the elements from this queue.boolean
contains(Object o)
Returnstrue
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, returningtrue
upon success andfalse
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.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.-
Methods inherited from class java.util.AbstractCollection
containsAll, isEmpty, removeAll, retainAll
-
-
-
-
Constructor Detail
-
ArrayBlockingQueue
public ArrayBlockingQueue(int capacity)
Creates anArrayBlockingQueue
with the given (fixed) capacity and default access policy.- Parameters:
capacity
- the capacity of this queue- Throws:
IllegalArgumentException
- ifcapacity < 1
-
ArrayBlockingQueue
public ArrayBlockingQueue(int capacity, boolean fair)
Creates anArrayBlockingQueue
with the given (fixed) capacity and the specified access policy.- Parameters:
capacity
- the capacity of this queuefair
- iftrue
then queue accesses for threads blocked on insertion or removal, are processed in FIFO order; iffalse
the access order is unspecified.- Throws:
IllegalArgumentException
- ifcapacity < 1
-
ArrayBlockingQueue
public ArrayBlockingQueue(int capacity, boolean fair, Collection<? extends E> c)
Creates anArrayBlockingQueue
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.- Parameters:
capacity
- the capacity of this queuefair
- iftrue
then queue accesses for threads blocked on insertion or removal, are processed in FIFO order; iffalse
the access order is unspecified.c
- the collection of elements to initially contain- Throws:
IllegalArgumentException
- ifcapacity
is less thanc.size()
, or less than 1.NullPointerException
- if the specified collection or any of its elements are null
-
-
Method Detail
-
add
public 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, returningtrue
upon success and throwing anIllegalStateException
if this queue is full.- Specified by:
add
in interfaceCollection<E>
- Specified by:
add
in interfaceBlockingQueue<E>
- Specified by:
add
in interfaceQueue<E>
- Overrides:
add
in classAbstractQueue<E>
- Parameters:
e
- the element to add- Returns:
true
(as specified byCollection.add(E)
)- Throws:
IllegalStateException
- if this queue is fullNullPointerException
- if the specified element is null
-
offer
public 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, returningtrue
upon success andfalse
if this queue is full. This method is generally preferable to methodadd(E)
, which can fail to insert an element only by throwing an exception.- Specified by:
offer
in interfaceBlockingQueue<E>
- Specified by:
offer
in interfaceQueue<E>
- Parameters:
e
- the element to add- Returns:
- true if the element was added to this queue, else false
- Throws:
NullPointerException
- if the specified element is null
-
put
public void put(E e) throws InterruptedException
Inserts the specified element at the tail of this queue, waiting for space to become available if the queue is full.- Specified by:
put
in interfaceBlockingQueue<E>
- Parameters:
e
- the element to add- Throws:
InterruptedException
- if interrupted while waitingNullPointerException
- if the specified element is null
-
offer
public boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException
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.- Specified by:
offer
in interfaceBlockingQueue<E>
- Parameters:
e
- the element to addtimeout
- how long to wait before giving up, in units of unitunit
- a TimeUnit determining how to interpret the timeout parameter- Returns:
- true if successful, or false if the specified waiting time elapses before space is available
- Throws:
InterruptedException
- if interrupted while waitingNullPointerException
- if the specified element is null
-
poll
public E poll()
Description copied from interface:Queue
Retrieves and removes the head of this queue, or returns null if this queue is empty.
-
take
public 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.- Specified by:
take
in interfaceBlockingQueue<E>
- Returns:
- the head of this queue
- Throws:
InterruptedException
- if interrupted while waiting
-
poll
public 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.- Specified by:
poll
in interfaceBlockingQueue<E>
- Parameters:
timeout
- how long to wait before giving up, in units of unitunit
- a TimeUnit determining how to interpret the timeout parameter- Returns:
- the head of this queue, or null if the specified waiting time elapses before an element is available
- Throws:
InterruptedException
- if interrupted while waiting
-
peek
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.
-
size
public int size()
Returns the number of elements in this queue.- Specified by:
size
in interfaceCollection<E>
- Specified by:
size
in classAbstractCollection<E>
- Returns:
- the number of elements in this queue
-
remainingCapacity
public int remainingCapacity()
Returns the number of additional elements that this queue can ideally (in the absence of memory or resource constraints) accept without blocking. This is always equal to the initial capacity of this queue less the currentsize
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.- Specified by:
remainingCapacity
in interfaceBlockingQueue<E>
- Returns:
- the remaining capacity
-
remove
public boolean remove(Object o)
Removes a single instance of the specified element from this queue, if it is present. More formally, removes an elemente
such thato.equals(e)
, if this queue contains one or more such elements. Returnstrue
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.
- Specified by:
remove
in interfaceCollection<E>
- Specified by:
remove
in interfaceBlockingQueue<E>
- Overrides:
remove
in classAbstractCollection<E>
- Parameters:
o
- element to be removed from this queue, if present- Returns:
true
if this queue changed as a result of the call
-
contains
public boolean contains(Object o)
Returnstrue
if this queue contains the specified element. More formally, returnstrue
if and only if this queue contains at least one elemente
such thato.equals(e)
.- Specified by:
contains
in interfaceCollection<E>
- Specified by:
contains
in interfaceBlockingQueue<E>
- Overrides:
contains
in classAbstractCollection<E>
- Parameters:
o
- object to be checked for containment in this queue- Returns:
true
if this queue contains the specified element
-
toArray
public Object[] toArray()
Returns an array containing all of the elements in this queue, in proper sequence.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.
- Specified by:
toArray
in interfaceCollection<E>
- Overrides:
toArray
in classAbstractCollection<E>
- Returns:
- an array containing all of the elements in this queue
-
toArray
public <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. If the queue fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this queue.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 ofString
:String[] y = x.toArray(new String[0]);
Note thattoArray(new Object[0])
is identical in function totoArray()
.- Specified by:
toArray
in interfaceCollection<E>
- Overrides:
toArray
in classAbstractCollection<E>
- Parameters:
a
- 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 purpose- Returns:
- an array containing all of the elements in this queue
- Throws:
ArrayStoreException
- 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 null
-
toString
public String toString()
Description copied from class:AbstractCollection
Returns a string representation of this collection. The string representation consists of a list of the collection's elements in the order they are returned by its iterator, enclosed in square brackets ("[]"). Adjacent elements are separated by the characters ", " (comma and space). Elements are converted to strings as byString.valueOf(Object)
.- Overrides:
toString
in classAbstractCollection<E>
- Returns:
- a string representation of this collection
-
clear
public void clear()
Atomically removes all of the elements from this queue. The queue will be empty after this call returns.- Specified by:
clear
in interfaceCollection<E>
- Overrides:
clear
in classAbstractQueue<E>
-
drainTo
public 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.- Specified by:
drainTo
in interfaceBlockingQueue<E>
- Parameters:
c
- the collection to transfer elements into- Returns:
- the number of elements transferred
- Throws:
UnsupportedOperationException
- 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 collection
-
drainTo
public 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.- Specified by:
drainTo
in interfaceBlockingQueue<E>
- Parameters:
c
- the collection to transfer elements intomaxElements
- the maximum number of elements to transfer- Returns:
- the number of elements transferred
- Throws:
UnsupportedOperationException
- 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 collection
-
iterator
public 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 a "weakly consistent" iterator that will never throwConcurrentModificationException
, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.- Specified by:
iterator
in interfaceIterable<E>
- Specified by:
iterator
in interfaceCollection<E>
- Specified by:
iterator
in classAbstractCollection<E>
- Returns:
- an iterator over the elements in this queue in proper sequence
-
-
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Dokument erstellt 11/06/2005, zuletzt geändert 04/03/2020
Quelle des gedruckten Dokuments:https://www.gaudry.be/de/java-api-rf-java/util/concurrent/arrayblockingqueue.html
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