edu.emory.mathcs.backport.java.util.concurrent
public class ArrayBlockingQueue extends AbstractQueue implements BlockingQueue, java.io.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.
Constructor and Description |
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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,
java.util.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.
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Modifier and Type | Method and Description |
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boolean |
add(java.lang.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.
|
void |
clear()
Atomically removes all of the elements from this queue.
|
boolean |
contains(java.lang.Object o)
Returns true if this queue contains the specified element.
|
int |
drainTo(java.util.Collection c)
Removes all available elements from this queue and adds them
to the given collection.
|
int |
drainTo(java.util.Collection c,
int maxElements)
Removes at most the given number of available elements from
this queue and adds them to the given collection.
|
java.util.Iterator |
iterator()
Returns an iterator over the elements in this queue in proper sequence.
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boolean |
offer(java.lang.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(java.lang.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.
|
java.lang.Object |
peek()
Retrieves, but does not remove, the head of this queue,
or returns null if this queue is empty.
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java.lang.Object |
poll()
Retrieves and removes the head of this queue,
or returns null if this queue is empty.
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java.lang.Object |
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(java.lang.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(java.lang.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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java.lang.Object |
take()
Retrieves and removes the head of this queue, waiting if necessary
until an element becomes available.
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java.lang.Object[] |
toArray()
Returns an array containing all of the elements in this queue, in
proper sequence.
|
java.lang.Object[] |
toArray(java.lang.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.
|
java.lang.String |
toString() |
addAll, element, remove
containsAll, isEmpty, removeAll, retainAll
public ArrayBlockingQueue(int capacity)
capacity
- the capacity of this queuejava.lang.IllegalArgumentException
- if capacity is less than 1public 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.java.lang.IllegalArgumentException
- if capacity is less than 1public ArrayBlockingQueue(int capacity, boolean fair, java.util.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 containjava.lang.IllegalArgumentException
- if capacity is less than
c.size(), or less than 1.java.lang.NullPointerException
- if the specified collection or any
of its elements are nullpublic boolean add(java.lang.Object e)
add
in interface BlockingQueue
add
in interface Queue
add
in interface java.util.Collection
add
in class AbstractQueue
e
- the element to addCollection.add(java.lang.Object)
)java.lang.IllegalStateException
- if this queue is fulljava.lang.NullPointerException
- if the specified element is nullpublic boolean offer(java.lang.Object e)
add(java.lang.Object)
,
which can fail to insert an element only by throwing an exception.offer
in interface BlockingQueue
offer
in interface Queue
e
- the element to addjava.lang.NullPointerException
- if the specified element is nullpublic void put(java.lang.Object e) throws java.lang.InterruptedException
put
in interface BlockingQueue
e
- the element to addjava.lang.InterruptedException
- if interrupted while waitingjava.lang.NullPointerException
- if the specified element is nullpublic boolean offer(java.lang.Object e, long timeout, TimeUnit unit) throws java.lang.InterruptedException
offer
in interface BlockingQueue
e
- the element to addtimeout
- how long to wait before giving up, in units of
unitunit
- a TimeUnit determining how to interpret the
timeout parameterjava.lang.InterruptedException
- if interrupted while waitingjava.lang.NullPointerException
- if the specified element is nullpublic java.lang.Object poll()
Queue
public java.lang.Object take() throws java.lang.InterruptedException
BlockingQueue
take
in interface BlockingQueue
java.lang.InterruptedException
- if interrupted while waitingpublic java.lang.Object poll(long timeout, TimeUnit unit) throws java.lang.InterruptedException
BlockingQueue
poll
in interface BlockingQueue
timeout
- how long to wait before giving up, in units of
unitunit
- a TimeUnit determining how to interpret the
timeout parameterjava.lang.InterruptedException
- if interrupted while waitingpublic java.lang.Object peek()
Queue
public int size()
size
in interface java.util.Collection
size
in class java.util.AbstractCollection
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
public boolean remove(java.lang.Object o)
remove
in interface BlockingQueue
remove
in interface java.util.Collection
remove
in class java.util.AbstractCollection
o
- element to be removed from this queue, if presentpublic boolean contains(java.lang.Object o)
contains
in interface BlockingQueue
contains
in interface java.util.Collection
contains
in class java.util.AbstractCollection
o
- object to be checked for containment in this queuepublic java.lang.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 java.util.Collection
toArray
in class AbstractCollection
public java.lang.Object[] toArray(java.lang.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 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 java.util.Collection
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 purposejava.lang.ArrayStoreException
- if the runtime type of the specified array
is not a supertype of the runtime type of every element in
this queuejava.lang.NullPointerException
- if the specified array is nullpublic java.lang.String toString()
toString
in class java.util.AbstractCollection
public void clear()
clear
in interface java.util.Collection
clear
in class AbstractQueue
public int drainTo(java.util.Collection c)
BlockingQueue
drainTo
in interface BlockingQueue
c
- the collection to transfer elements intojava.lang.UnsupportedOperationException
- if addition of elements
is not supported by the specified collectionjava.lang.ClassCastException
- if the class of an element of this queue
prevents it from being added to the specified collectionjava.lang.NullPointerException
- if the specified collection is nulljava.lang.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 int drainTo(java.util.Collection c, int maxElements)
BlockingQueue
drainTo
in interface BlockingQueue
c
- the collection to transfer elements intomaxElements
- the maximum number of elements to transferjava.lang.UnsupportedOperationException
- if addition of elements
is not supported by the specified collectionjava.lang.ClassCastException
- if the class of an element of this queue
prevents it from being added to the specified collectionjava.lang.NullPointerException
- if the specified collection is nulljava.lang.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 java.util.Iterator 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 java.lang.Iterable
iterator
in interface java.util.Collection
iterator
in class java.util.AbstractCollection