edu.emory.mathcs.backport.java.util.concurrent
public class ArrayBlockingQueue extends AbstractQueue implements BlockingQueue, 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 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
Constructor Summary | |
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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 | |
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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.
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void | clear()
Atomically removes all of the elements from this queue.
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boolean | contains(Object o)
Returns true if this queue contains the specified element.
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int | drainTo(Collection c) |
int | drainTo(Collection c, int maxElements) |
Iterator | iterator()
Returns an iterator over the elements in this queue in proper sequence.
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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. |
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.
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Object | peek() |
Object | poll() |
Object | poll(long timeout, TimeUnit unit) |
void | put(Object e)
Inserts the specified element at the tail of this queue, waiting
for space to become available if the queue is full.
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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.
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Object | take() |
Object[] | toArray()
Returns an array containing all of the elements in this queue, in
proper sequence.
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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. |
String | toString() |
Parameters: capacity the capacity of this queue
Throws: IllegalArgumentException if capacity is less than 1
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.
Throws: IllegalArgumentException if capacity is less than 1
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
Throws: IllegalArgumentException if capacity is less than c.size(), or less than 1. NullPointerException if the specified collection or any of its elements are null
Parameters: e the element to add
Returns: true (as specified by Collection#add)
Throws: IllegalStateException if this queue is full NullPointerException if the specified element is null
Parameters: o object to be checked for containment in this queue
Returns: true if this queue contains the specified element
Throws: UnsupportedOperationException {@inheritDoc } ClassCastException {@inheritDoc } NullPointerException {@inheritDoc } IllegalArgumentException {@inheritDoc }
Throws: UnsupportedOperationException {@inheritDoc } ClassCastException {@inheritDoc } NullPointerException {@inheritDoc } IllegalArgumentException {@inheritDoc }
Returns: an iterator over the elements in this queue in proper sequence
Throws: NullPointerException if the specified element is null
Throws: InterruptedException {@inheritDoc } NullPointerException {@inheritDoc }
Throws: InterruptedException {@inheritDoc } NullPointerException {@inheritDoc }
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.
Parameters: o element to be removed from this queue, if present
Returns: true if this queue changed as a result of the call
Returns: the number of elements in this queue
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.
Returns: an array containing all of the elements in 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().
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 queue NullPointerException if the specified array is null