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java.util.concurrent
Class LinkedBlockingQueue
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public class LinkedBlockingQueue<E>
extends AbstractQueue<E>
implements Serializable, BlockingQueue<E>
Type Parameters:
  • E - the type of elements held in this collection
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 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.

Since1.5
VersionNot specified.
AuthorDoug Lea
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Constructor Summary
LinkedBlockingQueue()
Creates a LinkedBlockingQueue with a capacity of MAX_VALUE .
LinkedBlockingQueue( int capacity )
Creates a LinkedBlockingQueue with the given (fixed) capacity.
LinkedBlockingQueue( Collection<? extends E> c )
Creates a LinkedBlockingQueue with a capacity of MAX_VALUE , 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.
int drainTo( Collection<? super E> c )
No description provided.
int drainTo( Collection<? super E> c, int maxElements )
No description provided.
Iterator<E> iterator()
Returns an iterator over the elements in this queue in proper sequence.
boolean offer( E 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.
boolean offer( E 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.
E peek()
No description provided.
E poll( long timeout, TimeUnit unit )
No description provided.
E poll()
No description provided.
void put( E e )
Inserts the specified element at the tail of this queue, waiting if necessary for space to become available.
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( 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()
No description provided.
Object[] toArray()
Returns an array containing all of the elements in this queue, in proper sequence.
T[] toArray( T [] 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.
String toString()
No description provided.
Methods inherited from java.utilAbstractCollection
Methods inherited from java.utilAbstractQueue
Methods inherited from java.util.concurrentBlockingQueue
Methods inherited from java.utilCollection
Methods inherited from java.langObject
Methods inherited from java.utilQueue
Constructor Detail
LinkedBlockingQueue
public LinkedBlockingQueue ( )
Creates a LinkedBlockingQueue with a capacity of MAX_VALUE .
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LinkedBlockingQueue
public LinkedBlockingQueue ( int capacity )
Creates a LinkedBlockingQueue with the given (fixed) capacity.
Parameters
TypeNameDescription
int capacity the capacity of this queue
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LinkedBlockingQueue
public LinkedBlockingQueue ( Collection<? extends E> c )
Creates a LinkedBlockingQueue with a capacity of MAX_VALUE , initially containing the elements of the given collection, added in traversal order of the collection's iterator.
Parameters
TypeNameDescription
Collection<? extends E> c the collection of elements to initially contain
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Method Detail
clear
public void clear ( )
Atomically removes all of the elements from this queue. The queue will be empty after this call returns.
Overrides method in AbstractQueue
Returns void No description provided.
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drainTo
public int drainTo ( Collection<? super E> c )
No description provided.
Implements method in BlockingQueue
Parameters
TypeNameDescription
Collection<? super E> c No description provided.
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drainTo
public int drainTo ( Collection<? super E> c, int maxElements )
No description provided.
Implements method in BlockingQueue
Parameters
TypeNameDescription
Collection<? super E> c No description provided.
int maxElements No description provided.
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iterator
public Iterator<E> 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.
Overrides method in AbstractCollection
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offer
public boolean offer ( E e, long timeout, TimeUnit unit )
throws
Inserts the specified element at the tail of this queue, waiting if necessary up to the specified wait time for space to become available.
Implements method in BlockingQueue
Parameters
TypeNameDescription
E e No description provided.
long timeout No description provided.
TimeUnit unit No description provided.
Exceptions
InterruptedException
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offer
public boolean offer ( E 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.
Implements method in Queue
Parameters
TypeNameDescription
E e No description provided.
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peek
public E peek ( )
No description provided.
Implements method in Queue
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poll
public E poll ( long timeout, TimeUnit unit )
throws
No description provided.
Implements method in BlockingQueue
Parameters
TypeNameDescription
long timeout No description provided.
TimeUnit unit No description provided.
Exceptions
InterruptedException No description provided.
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poll
public E poll ( )
No description provided.
Implements method in Queue
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put
public void put ( E e )
throws
Inserts the specified element at the tail of this queue, waiting if necessary for space to become available.
Implements method in BlockingQueue
Parameters
TypeNameDescription
E e No description provided.
Returns void No description provided.
Exceptions
InterruptedException
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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.

Implements method in BlockingQueue
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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).
Overrides method in AbstractCollection
Parameters
TypeNameDescription
Object o element to be removed from this queue, if present
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size
public int size ( )
Returns the number of elements in this queue.
Overrides method in AbstractCollection
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take
public E take ( )
throws
No description provided.
Implements method in BlockingQueue
Exceptions
InterruptedException No description provided.
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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.

Overrides method in AbstractCollection
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toArray
public <T> T[] toArray ( T [] 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().
Overrides method in AbstractCollection
Parameters
TypeNameDescription
T[] 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
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toString
public String toString ( )
No description provided.
Overrides method in AbstractCollection
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