LinkedBlockingQueue (Java 2 Platform SE 5.0) (original) (raw)
java.util.concurrent
Class LinkedBlockingQueue
java.lang.Object
java.util.AbstractCollection
java.util.AbstractQueue
java.util.concurrent.LinkedBlockingQueue
Type Parameters:
E
- the type of elements held in this collection
All Implemented Interfaces:
Serializable, Iterable, Collection, BlockingQueue, Queue
public class LinkedBlockingQueue
extends AbstractQueue
implements BlockingQueue, Serializable
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.
Since:
1.5
See Also:
Constructor Summary |
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LinkedBlockingQueue() Creates a LinkedBlockingQueue with a capacity ofInteger.MAX_VALUE. |
LinkedBlockingQueue(Collection<? extends E> c) Creates a LinkedBlockingQueue with a capacity ofInteger.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 | |
---|---|
void | clear() Atomically removes all of the elements from this queue. |
int | drainTo(Collection<? super E> c) Removes all available elements from this queue and adds them into the given collection. |
int | [drainTo](../../../java/util/concurrent/LinkedBlockingQueue.html#drainTo%28java.util.Collection, int%29)(Collection<? super E> c, int maxElements) Removes at most the given number of available elements from this queue and adds them into the given collection. |
Iterator<E> | iterator() Returns an iterator over the elements in this queue in proper sequence. |
boolean | offer(E o) Inserts the specified element at the tail of this queue if possible, returning immediately if this queue is full. |
boolean | [offer](../../../java/util/concurrent/LinkedBlockingQueue.html#offer%28E, long, java.util.concurrent.TimeUnit%29)(E 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. |
E | peek() Retrieves, but does not remove, the head of this queue, returning null if this queue is empty. |
E | poll() Retrieves and removes the head of this queue, or null if this queue is empty. |
E | [poll](../../../java/util/concurrent/LinkedBlockingQueue.html#poll%28long, java.util.concurrent.TimeUnit%29)(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(E 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(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. |
E | take() Retrieves and removes the head of this queue, waiting if no elements are present on this queue. |
Object[] | toArray() Returns an array containing all of the elements in this collection. |
T[] | toArray(T[] a) Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. |
String | toString() Returns a string representation of this collection. |
Methods inherited from class java.util.AbstractQueue |
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add, addAll, element, remove |
Methods inherited from class java.util.AbstractCollection |
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contains, 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](../../../java/lang/Object.html#wait%28long, int%29) |
Methods inherited from interface java.util.concurrent.BlockingQueue |
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add |
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, contains, containsAll, equals, hashCode, isEmpty, removeAll, retainAll |
Constructor Detail |
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LinkedBlockingQueue
public LinkedBlockingQueue()
Creates a LinkedBlockingQueue with a capacity ofInteger.MAX_VALUE.
LinkedBlockingQueue
public LinkedBlockingQueue(int capacity)
Creates a LinkedBlockingQueue with the given (fixed) capacity.
Parameters:
capacity
- the capacity of this queue.
Throws:
[IllegalArgumentException](../../../java/lang/IllegalArgumentException.html "class in java.lang")
- if capacity is not greater than zero.
LinkedBlockingQueue
public LinkedBlockingQueue(Collection<? extends E> c)
Creates a LinkedBlockingQueue with a capacity ofInteger.MAX_VALUE, initially containing the elements of the given collection, added in traversal order of the collection's iterator.
Parameters:
c
- the collection of elements to initially contain
Throws:
[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang")
- if c or any element within it is null
Method Detail |
---|
size
public int size()
Returns the number of elements in this queue.
Specified by:
[size](../../../java/util/Collection.html#size%28%29)
in interface [Collection](../../../java/util/Collection.html "interface in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Specified by:
[size](../../../java/util/AbstractCollection.html#size%28%29)
in class [AbstractCollection](../../../java/util/AbstractCollection.html "class in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Returns:
the number of elements in this queue.
remainingCapacity
public int remainingCapacity()
Returns the number of 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 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.
Specified by:
[remainingCapacity](../../../java/util/concurrent/BlockingQueue.html#remainingCapacity%28%29)
in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Returns:
the remaining capacity
put
public void put(E o) throws InterruptedException
Adds the specified element to the tail of this queue, waiting if necessary for space to become available.
Specified by:
[put](../../../java/util/concurrent/BlockingQueue.html#put%28E%29)
in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Parameters:
o
- the element to add
Throws:
[InterruptedException](../../../java/lang/InterruptedException.html "class in java.lang")
- if interrupted while waiting.
[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang")
- if the specified element is null.
offer
public boolean offer(E o, 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.
Specified by:
[offer](../../../java/util/concurrent/BlockingQueue.html#offer%28E, long, java.util.concurrent.TimeUnit%29)
in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Parameters:
o
- the element to add
timeout
- how long to wait before giving up, in units ofunit
unit
- a TimeUnit determining how to interpret thetimeout parameter
Returns:
true if successful, or false if the specified waiting time elapses before space is available.
Throws:
[InterruptedException](../../../java/lang/InterruptedException.html "class in java.lang")
- if interrupted while waiting.
[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang")
- if the specified element is null.
offer
public boolean offer(E o)
Inserts the specified element at the tail of this queue if possible, returning immediately if this queue is full.
Specified by:
[offer](../../../java/util/concurrent/BlockingQueue.html#offer%28E%29)
in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Specified by:
[offer](../../../java/util/Queue.html#offer%28E%29)
in interface [Queue](../../../java/util/Queue.html "interface in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Parameters:
o
- the element to add.
Returns:
true if it was possible to add the element to this queue, else false
Throws:
[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang")
- if the specified element is null
take
public E take() throws InterruptedException
Description copied from interface: [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html#take%28%29)
Retrieves and removes the head of this queue, waiting if no elements are present on this queue.
Specified by:
[take](../../../java/util/concurrent/BlockingQueue.html#take%28%29)
in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Returns:
the head of this queue
Throws:
[InterruptedException](../../../java/lang/InterruptedException.html "class in java.lang")
- if interrupted while waiting.
poll
public E poll(long timeout, TimeUnit unit) throws InterruptedException
Description copied from interface: [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html#poll%28long, java.util.concurrent.TimeUnit%29)
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.
Specified by:
[poll](../../../java/util/concurrent/BlockingQueue.html#poll%28long, java.util.concurrent.TimeUnit%29)
in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Parameters:
timeout
- how long to wait before giving up, in units ofunit
unit
- a TimeUnit determining how to interpret thetimeout parameter
Returns:
the head of this queue, or null if the specified waiting time elapses before an element is present.
Throws:
[InterruptedException](../../../java/lang/InterruptedException.html "class in java.lang")
- if interrupted while waiting.
poll
public E poll()
Description copied from interface: [Queue](../../../java/util/Queue.html#poll%28%29)
Retrieves and removes the head of this queue, or null if this queue is empty.
Specified by:
[poll](../../../java/util/Queue.html#poll%28%29)
in interface [Queue](../../../java/util/Queue.html "interface in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Returns:
the head of this queue, or null if this queue is empty.
peek
public E peek()
Description copied from interface: [Queue](../../../java/util/Queue.html#peek%28%29)
Retrieves, but does not remove, the head of this queue, returning null if this queue is empty.
Specified by:
[peek](../../../java/util/Queue.html#peek%28%29)
in interface [Queue](../../../java/util/Queue.html "interface in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Returns:
the head of this queue, or null if this queue is empty.
remove
public boolean remove(Object o)
Removes a single instance of the specified element from this queue, if it is present.
Specified by:
[remove](../../../java/util/Collection.html#remove%28java.lang.Object%29)
in interface [Collection](../../../java/util/Collection.html "interface in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Overrides:
[remove](../../../java/util/AbstractCollection.html#remove%28java.lang.Object%29)
in class [AbstractCollection](../../../java/util/AbstractCollection.html "class in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Parameters:
o
- element to be removed from this collection, if present.
Returns:
true if the collection contained the specified element.
toArray
public Object[] toArray()
Description copied from class: [AbstractCollection](../../../java/util/AbstractCollection.html#toArray%28%29)
Returns an array containing all of the elements in this collection. If the collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order. The returned array will be "safe" in that no references to it are maintained by the collection. (In other words, this method must allocate a new array even if the collection is backed by an Array). The caller is thus free to modify the returned array.
This implementation allocates the array to be returned, and iterates over the elements in the collection, storing each object reference in the next consecutive element of the array, starting with element 0.
Specified by:
[toArray](../../../java/util/Collection.html#toArray%28%29)
in interface [Collection](../../../java/util/Collection.html "interface in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Overrides:
[toArray](../../../java/util/AbstractCollection.html#toArray%28%29)
in class [AbstractCollection](../../../java/util/AbstractCollection.html "class in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Returns:
an array containing all of the elements in this collection.
toArray
public T[] toArray(T[] a)
Description copied from class: [AbstractCollection](../../../java/util/AbstractCollection.html#toArray%28T[]%29)
Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. If the collection 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 collection.
If the collection fits in the specified array with room to spare (i.e., the array has more elements than the collection), the element in the array immediately following the end of the collection is set tonull. This is useful in determining the length of the collection only if the caller knows that the collection does not contain any null elements.)
If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order.
This implementation checks if the array is large enough to contain the collection; if not, it allocates a new array of the correct size and type (using reflection). Then, it iterates over the collection, storing each object reference in the next consecutive element of the array, starting with element 0. If the array is larger than the collection, a null is stored in the first location after the end of the collection.
Specified by:
[toArray](../../../java/util/Collection.html#toArray%28T[]%29)
in interface [Collection](../../../java/util/Collection.html "interface in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Overrides:
[toArray](../../../java/util/AbstractCollection.html#toArray%28T[]%29)
in class [AbstractCollection](../../../java/util/AbstractCollection.html "class in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Parameters:
a
- the array into which the elements of the collection are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.
Returns:
an array containing the elements of the collection.
toString
public String toString()
Description copied from class: [AbstractCollection](../../../java/util/AbstractCollection.html#toString%28%29)
Returns a string representation of this collection. The string representation consists of a list of the collection's elements in the order they are returned by its iterator, enclosed in square brackets ("[]"). Adjacent elements are separated by the characters", " (comma and space). Elements are converted to strings as by String.valueOf(Object).
This implementation creates an empty string buffer, appends a left square bracket, and iterates over the collection appending the string representation of each element in turn. After appending each element except the last, the string ", " is appended. Finally a right bracket is appended. A string is obtained from the string buffer, and returned.
Overrides:
[toString](../../../java/util/AbstractCollection.html#toString%28%29)
in class [AbstractCollection](../../../java/util/AbstractCollection.html "class in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Returns:
a string representation of this collection.
clear
public void clear()
Atomically removes all of the elements from this queue. The queue will be empty after this call returns.
Specified by:
[clear](../../../java/util/Collection.html#clear%28%29)
in interface [Collection](../../../java/util/Collection.html "interface in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Overrides:
[clear](../../../java/util/AbstractQueue.html#clear%28%29)
in class [AbstractQueue](../../../java/util/AbstractQueue.html "class in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
drainTo
public int drainTo(Collection<? super E> c)
Description copied from interface: [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html#drainTo%28java.util.Collection%29)
Removes all available elements from this queue and adds them into the given collection. This operation may be more efficient than repeatedly polling this queue. A failure encountered while attempting to add elements to collection c may result in elements being in neither, either or both collections when the associated exception is thrown. Attempts to drain a queue to itself result inIllegalArgumentException. Further, the behavior of this operation is undefined if the specified collection is modified while the operation is in progress.
Specified by:
[drainTo](../../../java/util/concurrent/BlockingQueue.html#drainTo%28java.util.Collection%29)
in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Parameters:
c
- the collection to transfer elements into
Returns:
the number of elements transferred.
drainTo
public int drainTo(Collection<? super E> c, int maxElements)
Description copied from interface: [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html#drainTo%28java.util.Collection, int%29)
Removes at most the given number of available elements from this queue and adds them into the given collection. A failure encountered while attempting to add elements to collection c may result in elements being in neither, either or both collections when the associated exception is thrown. Attempts to drain a queue to itself result inIllegalArgumentException. Further, the behavior of this operation is undefined if the specified collection is modified while the operation is in progress.
Specified by:
[drainTo](../../../java/util/concurrent/BlockingQueue.html#drainTo%28java.util.Collection, int%29)
in interface [BlockingQueue](../../../java/util/concurrent/BlockingQueue.html "interface in java.util.concurrent")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Parameters:
c
- the collection to transfer elements into
maxElements
- the maximum number of elements to transfer
Returns:
the number of elements transferred.
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 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.
Specified by:
[iterator](../../../java/lang/Iterable.html#iterator%28%29)
in interface [Iterable](../../../java/lang/Iterable.html "interface in java.lang")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Specified by:
[iterator](../../../java/util/Collection.html#iterator%28%29)
in interface [Collection](../../../java/util/Collection.html "interface in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Specified by:
[iterator](../../../java/util/AbstractCollection.html#iterator%28%29)
in class [AbstractCollection](../../../java/util/AbstractCollection.html "class in java.util")<[E](../../../java/util/concurrent/LinkedBlockingQueue.html "type parameter in LinkedBlockingQueue")>
Returns:
an iterator over the elements in this queue in proper sequence.
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