java.util.AbstractCollection
java.util.AbstractQueue
java.util.concurrent.ArrayBlockingQueue
java.lang.Object
E - the type of elements held in this collectionA 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 can not be increased. Attempts to offer an element to a full queue will result in the offer operation blocking; attempts to retrieve an element from an empty queue will similarly block.
This class supports an optional fairness policy for ordering threads blocked on an insertion or removal. By default, this ordering is not guaranteed. However, an ArrayBlockingQueue constructed with fairness set to true grants blocked threads access in FIFO order. Fairness generally decreases throughput but reduces variability and avoids starvation.
This class implements all of the optional methods
of the Collection and Iterator interfaces.
| Constructor Summary | |
|---|---|
ArrayBlockingQueue(int capacity)
Creates an ArrayBlockingQueue with the given (fixed) capacity and default access policy. |
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ArrayBlockingQueue(int capacity,
boolean fair)
Creates an ArrayBlockingQueue with the given (fixed) capacity and the specified access policy. |
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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. |
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| Method Summary | ||
|---|---|---|
void |
clear()
Removes all of the elements from this collection. |
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boolean |
contains(Object o)
Returns true if this collection contains the specified element. |
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int |
drainTo(Collection<? super E> c)
Removes all available elements from this queue and adds them into the given collection. |
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int |
drainTo(Collection<? super E> c,
int maxElements)
Removes at most the given number of available elements from this queue and adds them into the given collection. |
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Iterator<E> |
iterator()
Returns an iterator over the elements in this queue in proper sequence. |
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boolean |
offer(E o)
Inserts the specified element at the tail of this queue if possible, returning immediately if this queue is full. |
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boolean |
offer(E o,
long timeout,
TimeUnit unit)
Inserts the specified element at the tail of this queue, waiting if necessary up to the specified wait time for space to become available. |
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E |
peek()
Retrieves, but does not remove, the head of this queue, returning null if this queue is empty. |
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E |
poll()
Retrieves and removes the head of this queue, or null if this queue is empty. |
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E |
poll(long timeout,
TimeUnit unit)
Retrieves and removes the head of this queue, waiting if necessary up to the specified wait time if no elements are present on this queue. |
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void |
put(E o)
Adds the specified element to the tail of this queue, waiting if necessary for space to become available. |
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int |
remainingCapacity()
Returns the number of elements that this queue can ideally (in the absence of memory or resource constraints) accept without blocking. |
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boolean |
remove(Object o)
Removes a single instance of the specified element from this collection, if it is present (optional operation). |
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int |
size()
Returns the number of elements in this queue. |
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E |
take()
Retrieves and removes the head of this queue, waiting if no elements are present on this queue. |
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Object[] |
toArray()
Returns an array containing all of the elements in this collection. |
|
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toArray(T[] a)
Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. |
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String |
toString()
Returns a string representation of this collection. |
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| Methods inherited from class java.util.AbstractQueue |
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add, addAll, element, remove |
| Methods inherited from class java.util.AbstractCollection |
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containsAll, isEmpty, removeAll, retainAll |
| Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
| Methods inherited from interface java.util.concurrent.BlockingQueue |
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add |
| Methods inherited from interface java.util.Queue |
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element, remove |
| Methods inherited from interface java.util.Collection |
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addAll, containsAll, equals, hashCode, isEmpty, removeAll, retainAll |
| Constructor Detail |
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public ArrayBlockingQueue(int capacity)
capacity - the capacity of this queue
IllegalArgumentException - if capacity is less than 1
public ArrayBlockingQueue(int capacity,
boolean fair)
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 is less than 1
public ArrayBlockingQueue(int capacity,
boolean fair,
Collection<? extends E> c)
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 contain
IllegalArgumentException - if capacity is less than
c.size(), or less than 1.
NullPointerException - if c or any element within it
is null| Method Detail |
|---|
public boolean offer(E o)
offer in interface BlockingQueueo - the element to add.
NullPointerException - if the specified element is null
public boolean offer(E o,
long timeout,
TimeUnit unit)
throws InterruptedException
offer in interface BlockingQueueo - the element to addtimeout - how long to wait before giving up, in units of
unitunit - a TimeUnit determining how to interpret the
timeout parameter
InterruptedException - if interrupted while waiting.
NullPointerException - if the specified element is null.public E poll()
Queue
poll in interface Queue
public E poll(long timeout,
TimeUnit unit)
throws InterruptedException
BlockingQueue
poll in interface BlockingQueuetimeout - how long to wait before giving up, in units of
unitunit - a TimeUnit determining how to interpret the
timeout parameter
InterruptedException - if interrupted while waiting.public boolean remove(Object o)
AbstractCollectionThis implementation iterates over the collection looking for the specified element. If it finds the element, it removes the element from the collection using the iterator's remove method.
Note that this implementation throws an UnsupportedOperationException if the iterator returned by this collection's iterator method does not implement the remove method and this collection contains the specified object.
remove in interface Collectionremove in class AbstractCollectiono - element to be removed from this collection, if present.
public E peek()
Queue
peek in interface Queue
public E take()
throws InterruptedException
BlockingQueue
take in interface BlockingQueueInterruptedException - if interrupted while waiting.
public void put(E o)
throws InterruptedException
put in interface BlockingQueueo - the element to add
InterruptedException - if interrupted while waiting.
NullPointerException - if the specified element is null.public int size()
size in interface Collectionsize in class AbstractCollectionpublic int remainingCapacity()
Note that you cannot always tell if an attempt to add an element will succeed by inspecting remainingCapacity because it may be the case that a waiting consumer is ready to take an element out of an otherwise full queue.
remainingCapacity in interface BlockingQueuepublic boolean contains(Object o)
AbstractCollectionThis implementation iterates over the elements in the collection, checking each element in turn for equality with the specified element.
contains in interface Collectioncontains in class AbstractCollectiono - object to be checked for containment in this collection.
public Object[] toArray()
AbstractCollectionThis implementation allocates the array to be returned, and iterates over the elements in the collection, storing each object reference in the next consecutive element of the array, starting with element 0.
toArray in interface CollectiontoArray in class AbstractCollectionpublic <T> T[] toArray(T[] a)
AbstractCollectionIf the collection fits in the specified array with room to spare (i.e., the array has more elements than the collection), the element in the array immediately following the end of the collection is set to null. This is useful in determining the length of the collection only if the caller knows that the collection does not contain any null elements.)
If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order.
This implementation checks if the array is large enough to contain the collection; if not, it allocates a new array of the correct size and type (using reflection). Then, it iterates over the collection, storing each object reference in the next consecutive element of the array, starting with element 0. If the array is larger than the collection, a null is stored in the first location after the end of the collection.
toArray in interface CollectiontoArray in class AbstractCollectiona - the array into which the elements of the collection are to
be stored, if it is big enough; otherwise, a new array of the
same runtime type is allocated for this purpose.
public String toString()
AbstractCollectionThis implementation creates an empty string buffer, appends a left square bracket, and iterates over the collection appending the string representation of each element in turn. After appending each element except the last, the string ", " is appended. Finally a right bracket is appended. A string is obtained from the string buffer, and returned.
toString in class AbstractCollectionpublic void clear()
AbstractQueueThis implementation repeatedly invokes poll until it
returns null.
clear in interface Collectionclear in class AbstractQueuepublic int drainTo(Collection<? super E> c)
BlockingQueue
drainTo in interface BlockingQueuec - the collection to transfer elements into
public int drainTo(Collection<? super E> c,
int maxElements)
BlockingQueue
drainTo in interface BlockingQueuec - the collection to transfer elements intomaxElements - the maximum number of elements to transfer
public Iterator<E> iterator()
ConcurrentModificationException,
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.
iterator in interface Collectioniterator in class AbstractCollection