edu.emory.mathcs.backport.java.util.concurrent
Class LinkedBlockingQueue
java.util.AbstractCollection
- BlockingQueue, Collection, Queue, java.io.Serializable
public class 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
../../../../../../../../guide/collections/index.html">
Java Collections Framework.
LinkedBlockingQueue() - Creates a LinkedBlockingQueue with a capacity of
Integer.MAX_VALUE .
|
LinkedBlockingQueue(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.
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void | clear() - Atomically removes all of the elements from this queue.
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int | drainTo(Collection c)
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int | drainTo(Collection c, int maxElements)
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Iterator | iterator() - Returns an iterator over the elements in this queue in proper sequence.
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boolean | offer(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.
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boolean | offer(Object e, 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.
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Object | peek() - Retrieves, but does not remove, the head of this queue,
or returns null if this queue is empty.
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Object | poll() - Retrieves and removes the head of this queue,
or returns null if this queue is empty.
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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(Object e) - Inserts the specified element at the tail of this queue, waiting if
necessary for space to become available.
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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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Object | 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.
|
Object[] | toArray(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.
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String | toString()
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LinkedBlockingQueue
public LinkedBlockingQueue()
Creates a LinkedBlockingQueue with a capacity of
Integer.MAX_VALUE
.
LinkedBlockingQueue
public LinkedBlockingQueue(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.
c
- the collection of elements to initially contain
LinkedBlockingQueue
public LinkedBlockingQueue(int capacity)
Creates a LinkedBlockingQueue with the given (fixed) capacity.
capacity
- the capacity of this queue
clear
public void clear()
Atomically removes all of the elements from this queue.
The queue will be empty after this call returns.
- clear in interface AbstractQueue
iterator
public Iterator iterator()
Returns an iterator over the elements in this queue in proper sequence.
The returned Iterator is a "weakly consistent" iterator that
will never throw java.util.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.
- an iterator over the elements in this queue in proper sequence
offer
public boolean offer(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.
When using a capacity-restricted queue, this method is generally
preferable to method
add
, which can fail to
insert an element only by throwing an exception.
- offer in interface BlockingQueue
- offer in interface Queue
offer
public boolean offer(Object e,
long timeout,
TimeUnit unit)
throws InterruptedException
Inserts the specified element at the tail of this queue, waiting if
necessary up to the specified wait time for space to become available.
- offer in interface BlockingQueue
- true if successful, or false if
the specified waiting time elapses before space is available.
peek
public Object peek()
Retrieves, but does not remove, the head of this queue,
or returns null if this queue is empty.
- peek in interface Queue
- the head of this queue, or null if this queue is empty
poll
public Object poll()
Retrieves and removes the head of this queue,
or returns null if this queue is empty.
- poll in interface Queue
- the head of this queue, or null if this queue is empty
poll
public Object poll(long timeout,
TimeUnit unit)
throws InterruptedException
Retrieves and removes the head of this queue, waiting up to the
specified wait time if necessary for an element to become available.
- 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
- the head of this queue, or null if the
specified waiting time elapses before an element is available
put
public void put(Object e)
throws InterruptedException
Inserts the specified element at the tail of this queue, waiting if
necessary for space to become available.
- put in interface BlockingQueue
remainingCapacity
public int remainingCapacity()
Returns the number of additional elements that this queue can ideally
(in the absence of memory or resource constraints) accept without
blocking. This is always equal to the initial capacity of this queue
less the current
size of this queue.
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
remove
public boolean remove(Object o)
Removes a single instance of the specified element from this queue,
if it is present. More formally, removes an element e such
that o.equals(e), if this queue contains one or more such
elements.
Returns true if this queue contained the specified element
(or equivalently, if this queue changed as a result of the call).
- remove in interface BlockingQueue
o
- element to be removed from this queue, if present
- true if this queue changed as a result of the call
size
public int size()
Returns the number of elements in this queue.
- the number of elements in this queue
take
public Object take()
throws InterruptedException
Retrieves and removes the head of this queue, waiting if necessary
until an element becomes available.
- take in interface BlockingQueue
toArray
public Object[] toArray()
Returns an array containing all of the elements in this queue, in
proper sequence.
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 AbstractCollection
- an array containing all of the elements in this queue
toArray
public Object[] toArray(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. If the queue fits in the specified array, it
is returned therein. Otherwise, a new array is allocated with the
runtime type of the specified array and the size of this queue.
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 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 purpose
- an array containing all of the elements in this queue
toString
public String toString()