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java.util.concurrent
class ArrayBlockingQueue

java.lang.Object extended by java.util.AbstractCollection extended by java.util.AbstractQueue extended by java.util.concurrent.ArrayBlockingQueue
All Implemented Interfaces:
Serializable, Collection, Queue, BlockingQueue

public class ArrayBlockingQueue
extends AbstractQueue
implements BlockingQueue, Serializable

A bounded {@linkplain BlockingQueue 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 increased. 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 {@link Collection} and {@link Iterator} interfaces.

This class is a member of the Java Collections Framework.


Constructor Summary
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 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.
 
Method Summary
 boolean

          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

          Atomically removes all of the elements from this queue.
 boolean

          Returns true if this queue contains the specified element.
 int

          
 int
drainTo(Collection c, int maxElements)

          
 Iterator

          Returns an iterator over the elements in this queue in proper sequence.
 boolean

          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(Object 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.
 Object

          
 Object

          
 Object
poll(long timeout, TimeUnit unit)

          
 void

          Inserts the specified element at the tail of this queue, waiting for space to become available if the queue is full.
 int

          Returns the number of additional elements that this queue can ideally (in the absence of memory or resource constraints) accept without blocking.
 boolean

          Removes a single instance of the specified element from this queue, if it is present.
 int

          Returns the number of elements in this queue.
 Object

          
 Object[]

          Returns an array containing all of the elements in this queue, in proper sequence.
 Object[]

          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

          Returns a string representation of this collection.
 
Methods inherited from class java.util.AbstractQueue
add, addAll, clear, element, remove
 
Methods inherited from class java.util.AbstractCollection
add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ArrayBlockingQueue

public ArrayBlockingQueue(int capacity)
Creates an ArrayBlockingQueue with the given (fixed) capacity and default access policy.

Parameters:
capacity - the capacity of this queue

ArrayBlockingQueue

public ArrayBlockingQueue(int capacity,
                          boolean fair)
Creates an ArrayBlockingQueue with the given (fixed) capacity and the specified access policy.

Parameters:
capacity - the capacity of this queue
fair - if true then queue accesses for threads blocked on insertion or removal, are processed in FIFO order; if false the access order is unspecified.

ArrayBlockingQueue

public ArrayBlockingQueue(int capacity,
                          boolean fair,
                          Collection 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.

Parameters:
capacity - the capacity of this queue
fair - 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
Method Detail

add

public boolean add(Object 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.

Overrides:
add in class AbstractQueue
Parameters:
e - the element to add
Returns:
true (as specified by {@link Collection#add})

clear

public void clear()
Atomically removes all of the elements from this queue. The queue will be empty after this call returns.

Overrides:
clear in class AbstractQueue

contains

public 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).

Overrides:
contains in class AbstractCollection
Parameters:
o - object to be checked for containment in this queue
Returns:
true if this queue contains the specified element

drainTo

public int drainTo(Collection c)
Parameters:
c

drainTo

public int drainTo(Collection c,
                   int maxElements)
Parameters:
c
maxElements

iterator

public Iterator iterator()
Returns an iterator over the elements in this queue in proper sequence. The returned Iterator is a "weakly consistent" iterator that will never throw {@link 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.

Overrides:
iterator in class AbstractCollection
Returns:
an iterator over the elements in this queue in proper sequence

offer

public boolean offer(Object 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. This method is generally preferable to method {@link #add}, which can fail to insert an element only by throwing an exception.

Parameters:
e

offer

public boolean offer(Object 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.

Parameters:
e
timeout
unit
Throws:
InterruptedException - {@inheritDoc}

peek

public Object peek()

poll

public Object poll()

poll

public Object poll(long timeout,
                   TimeUnit unit)
            throws InterruptedException
Parameters:
timeout
unit
Throws:
InterruptedException

put

public void put(Object e)
         throws InterruptedException
Inserts the specified element at the tail of this queue, waiting for space to become available if the queue is full.

Parameters:
e
Throws:
InterruptedException - {@inheritDoc}

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 current 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.


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 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).

Overrides:
remove in class AbstractCollection
Parameters:
o - element to be removed from this queue, if present
Returns:
true if this queue changed as a result of the call

size

public int size()
Returns the number of elements in this queue.

Overrides:
size in class AbstractCollection
Returns:
the number of elements in this queue

take

public Object take()
            throws InterruptedException
Throws:
InterruptedException

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.

Overrides:
toArray in class AbstractCollection
Returns:
an array containing all of the elements in this queue

toArray

public Object[] toArray(Object[] 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 {@link #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().

Overrides:
toArray in class AbstractCollection
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

toString

public String toString()
Overrides:
toString in class AbstractCollection


This documentation differs from the official API. Jadeite adds extra features to the API including: variable font sizes, constructions examples, placeholders for classes and methods, and auto-generated “See Also” links. Additionally it is missing some items found in standard Javadoc documentation, including: generics type information, “Deprecated” tags and comments, “See Also” links, along with other minor differences. Please send any questions or feedback to bam@cs.cmu.edu.
This page displays the Jadeite version of the documention, which is derived from the offical documentation that contains this copyright notice:
Copyright 2008 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
The official Sun™ documentation can be found here at http://java.sun.com/javase/6/docs/api/.