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java.lang.Object | +--java.util.AbstractCollection | +--edu.emory.mathcs.util.AbstractQueue | +--edu.emory.mathcs.util.concurrent.LinkedBlockingQueue
An optionally-bounded blocking queue based on linked nodes. 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. Linked queues typically have higher throughput than array-based queues but less predictable performance in most concurrent applications.
The optional capacity bound constructor argument serves as a
way to prevent excessive queue expansion. The capacity, if unspecified,
is equal to Integer.MAX_VALUE
. Linked nodes are
dynamically created upon each insertion unless this would bring the
queue above capacity.
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.
Field Summary | |
protected int |
capacity_
Number of elements allowed |
protected edu.emory.mathcs.util.concurrent.LinkedBlockingQueue.LinkedNode |
head_
Dummy header node of list. |
protected edu.emory.mathcs.util.concurrent.LinkedBlockingQueue.LinkedNode |
last_
The last node of list. |
protected java.lang.Object |
putGuard_
Helper monitor. |
protected int |
putSidePutPermits_
One side of a split permit count. |
protected java.lang.Object |
takeGuard_
Helper monitor. |
protected int |
takeSidePutPermits_
Number of takes since last reconcile |
Constructor Summary | |
LinkedBlockingQueue()
Creates a LinkedBlockingQueue with a capacity of Integer.MAX_VALUE . |
|
LinkedBlockingQueue(java.util.Collection c)
Creates a LinkedBlockingQueue with a capacity of Integer.MAX_VALUE , initially containing the elements of the
given collection,
added in traversal order of the collection's iterator. |
|
LinkedBlockingQueue(int capacity)
Creates a LinkedBlockingQueue with the given (fixed) capacity. |
Method Summary | |
protected void |
allowTake()
Notify a waiting take if needed |
void |
clear()
Atomically removes all of the elements from this queue. |
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. |
protected java.lang.Object |
extract()
Main mechanics for take/poll |
protected void |
insert(java.lang.Object x)
Create and insert a node. |
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. |
protected int |
reconcilePutPermits()
Move put permits from take side to put side; return the number of put side permits that are 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 |
contains, 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, contains, containsAll, equals, hashCode, isEmpty, removeAll, retainAll |
Field Detail |
protected transient edu.emory.mathcs.util.concurrent.LinkedBlockingQueue.LinkedNode head_
protected transient edu.emory.mathcs.util.concurrent.LinkedBlockingQueue.LinkedNode last_
protected final java.lang.Object putGuard_
protected final java.lang.Object takeGuard_
protected int capacity_
protected transient int putSidePutPermits_
protected transient int takeSidePutPermits_
Constructor Detail |
public LinkedBlockingQueue()
Integer.MAX_VALUE
.
public LinkedBlockingQueue(int capacity)
capacity
- the capacity of this queue.
java.lang.IllegalArgumentException
- if capacity is not greater
than zero.public LinkedBlockingQueue(java.util.Collection c)
Integer.MAX_VALUE
, initially containing the elements of the
given collection,
added in traversal order of the collection's iterator.
c
- the collection of elements to initially contain
java.lang.NullPointerException
- if c or any element within it
is nullMethod Detail |
protected final int reconcilePutPermits()
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
protected final void allowTake()
protected void insert(java.lang.Object x)
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 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 boolean offer(java.lang.Object o)
offer
in interface BlockingQueue
o
- the element to add.
java.lang.NullPointerException
- if the specified element is nullprotected java.lang.Object extract()
public java.lang.Object take() throws java.lang.InterruptedException
BlockingQueue
take
in interface BlockingQueue
java.lang.InterruptedException
- if interrupted while waiting.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 java.lang.Object poll()
Queue
poll
in interface Queue
public java.lang.Object peek()
Queue
peek
in interface Queue
public boolean remove(java.lang.Object o)
remove
in interface java.util.Collection
remove
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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