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java.lang.Object | +--java.util.AbstractCollection | +--edu.emory.mathcs.util.AbstractQueue | +--edu.emory.mathcs.util.concurrent.ArrayBlockingQueue
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 to a full queue will result in the put operation blocking; attempts to retrieve 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. |
|
ArrayBlockingQueue(int capacity,
boolean fair)
Creates an ArrayBlockingQueue with the given (fixed) capacity and the specified access policy. |
|
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. |
Method Summary | |
void |
clear()
Atomically removes all of the elements from this queue. |
boolean |
contains(java.lang.Object o)
|
int |
drainTo(java.util.Collection c)
Removes all available elements from this queue and adds them into 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 into the given collection. |
java.util.Iterator |
iterator()
Returns an iterator over the elements in this queue in proper sequence. |
boolean |
offer(java.lang.Object o)
Inserts the specified element at the tail of this queue if possible, returning immediately if this queue is full. |
boolean |
offer(java.lang.Object o,
long timeout,
TimeUnit unit)
Inserts the specified element at the tail of this queue, waiting if necessary up to the specified wait time for space to become available. |
java.lang.Object |
peek()
Retrieves, but does not remove, the head of this queue, returning null if this queue is empty. |
java.lang.Object |
poll()
Retrieves and removes the head of this queue, or null if this queue is empty. |
java.lang.Object |
poll(long timeout,
TimeUnit unit)
Retrieves and removes the head of this queue, waiting if necessary up to the specified wait time if no elements are present on this queue. |
void |
put(java.lang.Object o)
Adds the specified element to the tail of this queue, waiting if necessary for space to become available. |
int |
remainingCapacity()
Returns the number of 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. |
java.lang.Object |
take()
Retrieves and removes the head of this queue, waiting if no elements are present on this queue. |
java.lang.Object[] |
toArray()
|
java.lang.Object[] |
toArray(java.lang.Object[] a)
|
java.lang.String |
toString()
|
Methods inherited from class edu.emory.mathcs.util.AbstractQueue |
add, addAll, element, remove |
Methods inherited from class java.util.AbstractCollection |
containsAll, isEmpty, removeAll, retainAll |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Methods inherited from interface edu.emory.mathcs.util.concurrent.BlockingQueue |
add |
Methods inherited from interface edu.emory.mathcs.util.Queue |
element, remove |
Methods inherited from interface java.util.Collection |
addAll, containsAll, equals, hashCode, isEmpty, removeAll, retainAll |
Constructor Detail |
public ArrayBlockingQueue(int capacity)
capacity
- the capacity of this queue
java.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 contain
java.lang.IllegalArgumentException
- if capacity is less than
c.size(), or less than 1.
java.lang.NullPointerException
- if c or any element within it
is nullMethod Detail |
public boolean offer(java.lang.Object o)
offer
in interface BlockingQueue
o
- the element to add.
java.lang.NullPointerException
- if the specified element is nullpublic boolean offer(java.lang.Object o, long timeout, TimeUnit unit) throws java.lang.InterruptedException
offer
in interface BlockingQueue
o
- the element to addtimeout
- how long to wait before giving up, in units of
unitunit
- a TimeUnit determining how to interpret the
timeout parameter
java.lang.InterruptedException
- if interrupted while waiting.
java.lang.NullPointerException
- if the specified element is null.public java.lang.Object poll()
Queue
poll
in interface Queue
public 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 parameter
java.lang.InterruptedException
- if interrupted while waiting.public boolean remove(java.lang.Object o)
remove
in interface java.util.Collection
remove
in class java.util.AbstractCollection
public java.lang.Object peek()
Queue
peek
in interface Queue
public java.lang.Object take() throws java.lang.InterruptedException
BlockingQueue
take
in interface BlockingQueue
java.lang.InterruptedException
- if interrupted while waiting.public void put(java.lang.Object o) throws java.lang.InterruptedException
put
in interface BlockingQueue
o
- the element to add
java.lang.InterruptedException
- if interrupted while waiting.
java.lang.NullPointerException
- if the specified element is null.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 add an element will succeed by inspecting remainingCapacity because it may be the case that a waiting consumer is ready to take an element out of an otherwise full queue.
remainingCapacity
in interface BlockingQueue
public boolean contains(java.lang.Object o)
contains
in interface java.util.Collection
contains
in class java.util.AbstractCollection
public java.lang.Object[] toArray()
toArray
in interface java.util.Collection
toArray
in class java.util.AbstractCollection
public java.lang.Object[] toArray(java.lang.Object[] a)
toArray
in interface java.util.Collection
toArray
in class java.util.AbstractCollection
public 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 into
public 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 transfer
public 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.util.Collection
iterator
in class java.util.AbstractCollection
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