java.util.AbstractCollection<E>
java.util.AbstractQueue<E>
java.util.concurrent.ArrayBlockingQueue<E>
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Java™ Platform Standard Ed. 6 |
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java.lang.Object
E - the type of elements held in this collectionpublic class ArrayBlockingQueue<E>
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.
| 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 | ||
|---|---|---|
boolean |
add(E 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<? super E> c)
Removes all available elements from this queue and adds them to 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 to 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 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. |
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boolean |
offer(E 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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E |
peek()
Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty. |
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E |
poll()
Retrieves and removes the head of this queue, or returns 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 up to the specified wait time if necessary for an element to become available. |
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void |
put(E 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. |
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boolean |
remove(Object o)
Removes a single instance of the specified element from this queue, if it is present. |
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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 necessary until an element becomes available. |
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Object[] |
toArray()
Returns an array containing all of the elements in this queue, in proper sequence. |
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toArray(T[] 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. |
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String |
toString()
Returns a string representation of this collection. |
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| Methods inherited from class java.util.AbstractQueue |
|---|
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.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 |
|---|
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 the specified collection or any
of its elements are null| Method Detail |
|---|
public boolean add(E e)
add in interface Collection<E>add in interface BlockingQueue<E>add in interface Queue<E>add in class AbstractQueue<E>e - the element to add
Collection.add(E))
IllegalStateException - if this queue is full
NullPointerException - if the specified element is nullpublic boolean offer(E e)
add(E),
which can fail to insert an element only by throwing an exception.
offer in interface BlockingQueue<E>offer in interface Queue<E>e - the element to add
NullPointerException - if the specified element is null
public void put(E e)
throws InterruptedException
put in interface BlockingQueue<E>e - the element to add
InterruptedException - if interrupted while waiting
NullPointerException - if the specified element is null
public boolean offer(E e,
long timeout,
TimeUnit unit)
throws InterruptedException
offer in interface BlockingQueue<E>e - 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 nullpublic E poll()
Queue
poll in interface Queue<E>
public E take()
throws InterruptedException
BlockingQueue
take in interface BlockingQueue<E>InterruptedException - if interrupted while waiting
public E poll(long timeout,
TimeUnit unit)
throws InterruptedException
BlockingQueue
poll in interface BlockingQueue<E>timeout - how long to wait before giving up, in units of
unitunit - a TimeUnit determining how to interpret the
timeout parameter
InterruptedException - if interrupted while waitingpublic E peek()
Queue
peek in interface Queue<E>public int size()
size in interface Collection<E>size in class AbstractCollection<E>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.
remainingCapacity in interface BlockingQueue<E>public boolean remove(Object o)
remove in interface Collection<E>remove in interface BlockingQueue<E>remove in class AbstractCollection<E>o - element to be removed from this queue, if present
public boolean contains(Object o)
contains in interface Collection<E>contains in interface BlockingQueue<E>contains in class AbstractCollection<E>o - object to be checked for containment in this queue
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 interface Collection<E>toArray in class AbstractCollection<E>public <T> T[] toArray(T[] 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 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 interface Collection<E>toArray in class AbstractCollection<E>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
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 nullpublic String toString()
AbstractCollectionString.valueOf(Object).
toString in class AbstractCollection<E>public void clear()
clear in interface Collection<E>clear in class AbstractQueue<E>public int drainTo(Collection<? super E> c)
BlockingQueue
drainTo in interface BlockingQueue<E>c - the collection to transfer elements into
UnsupportedOperationException - if addition of elements
is not supported by the specified collection
ClassCastException - if the class of an element of this queue
prevents it from being added to the specified collection
NullPointerException - if the specified collection is null
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<? super E> c,
int maxElements)
BlockingQueue
drainTo in interface BlockingQueue<E>c - the collection to transfer elements intomaxElements - the maximum number of elements to transfer
UnsupportedOperationException - if addition of elements
is not supported by the specified collection
ClassCastException - if the class of an element of this queue
prevents it from being added to the specified collection
NullPointerException - if the specified collection is null
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 collectionpublic 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 Iterable<E>iterator in interface Collection<E>iterator in class AbstractCollection<E>
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Java™ Platform Standard Ed. 6 |
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