java.util.concurrent.ArrayBlockingQueue<E>

public class java.util.concurrent

ArrayBlockingQueue<E>

Java SE 6

Extends: AbstractCollection > AbstractQueue

Implements: BlockingQueue, 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 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 Collection and Iterator interfaces.

This class is a member of the Java Collections Framework.

since 1.5

E the type of elements held in this collection

Constructors

public

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

capacity	the capacity of this queue
Throws	IllegalArgumentException: if `capacity` is less than 1

public

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

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.
Throws	IllegalArgumentException: if `capacity` is less than 1

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.

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
Throws	IllegalArgumentException: if `capacity` is less than `c.size()`, or less than 1.
Throws	NullPointerException: if the specified collection or any of its elements are null

Methods

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.

e	the element to add
return	`true` (as specified by `Collection#add`)
Throws	IllegalStateException: if this queue is full
Throws	NullPointerException: als het gespecifieerde element null is

public void

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

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).

o	object to be checked for containment in this queue
return	`true` if this queue contains the specified element

public int

drainTo(Collection c)

Throws	UnsupportedOperationException: if addition of elements is not supported by the specified collection
Throws	ClassCastException: if the class of an element of this queue prevents it from being added to the specified collection
Throws	NullPointerException: if the specified collection is null
Throws	IllegalArgumentException: 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

public int

drainTo(Collection c, int maxElements)

Throws	UnsupportedOperationException: if addition of elements is not supported by the specified collection
Throws	ClassCastException: if the class of an element of this queue prevents it from being added to the specified collection
Throws	NullPointerException: if the specified collection is null
Throws	IllegalArgumentException: 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

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 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.

return

an iterator over the elements in this queue in proper sequence

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 #add, which can fail to insert an element only by throwing an exception.

Throws

NullPointerException: als het gespecifieerde element null is

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.

Throws	InterruptedException: if interrupted while waiting
Throws	NullPointerException: als het gespecifieerde element null is

public Object

peek()

public Object

poll()

public Object

poll(long timeout, TimeUnit unit) throws InterruptedException

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.

Throws	InterruptedException: if interrupted while waiting
Throws	NullPointerException: als het gespecifieerde element null is

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.

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).

o	element to be removed from this queue, if present
return	`true` if this queue changed as a result of the call

public int

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

return

the number of elements in this queue

public Object

take() throws InterruptedException

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.

return an array containing all of the elements in this queue

public Object[]<T>

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 #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().

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
return	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 queue
Throws	NullPointerException: if the specified array is null

public String

toString()

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Java SE 6

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