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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 | |
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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 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 |
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 |
clear() Atomically removes all of the elements from this queue. |
boolean |
Returns true if this queue contains the specified element. |
int |
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int |
drainTo(Collection c, int maxElements) |
Iterator |
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 |
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 |
peek() |
Object |
poll() |
Object |
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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 |
size() Returns the number of elements in this queue. |
Object |
take() |
Object[] |
toArray() 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 |
toString() Returns a string representation of this collection. |
Methods inherited from class java.util.AbstractQueue |
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add, addAll, clear, element, remove |
Methods inherited from class java.util.AbstractCollection |
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add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray, toString |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public ArrayBlockingQueue(int capacity)
capacity
- the capacity of this queuepublic 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.public ArrayBlockingQueue(int capacity, boolean fair, Collection 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 containMethod Detail |
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public boolean add(Object e)
add
in class AbstractQueue
e
- the element to addpublic void clear()
clear
in class AbstractQueue
public boolean contains(Object o)
contains
in class AbstractCollection
o
- object to be checked for containment in this queuepublic int drainTo(Collection c)
c
public int drainTo(Collection c, int maxElements)
c
maxElements
public Iterator iterator()
iterator
in class AbstractCollection
public boolean offer(Object e)
e
public boolean offer(Object e, long timeout, TimeUnit unit) throws InterruptedException
e
timeout
unit
InterruptedException
- {@inheritDoc}public Object peek()
public Object poll()
public Object poll(long timeout, TimeUnit unit) throws InterruptedException
timeout
unit
InterruptedException
public void put(Object e) throws InterruptedException
e
InterruptedException
- {@inheritDoc}public int remainingCapacity()
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)
remove
in class AbstractCollection
o
- element to be removed from this queue, if presentpublic int size()
size
in class AbstractCollection
public Object take() throws InterruptedException
InterruptedException
public Object[] toArray()
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.
toArray
in class AbstractCollection
public Object[] toArray(Object[] a)
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().
toArray
in class AbstractCollection
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 purposepublic String toString()
toString
in class AbstractCollection
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