java.util.concurrent
class LinkedBlockingQueue

java.lang.Object java.util.AbstractCollection java.util.AbstractQueue java.util.concurrent.LinkedBlockingQueue

All Implemented Interfaces:

Serializable, Collection, Queue, BlockingQueue

Most common way to construct:

LinkedBlockingQueue queue = new LinkedBlockingQueue();

Based on 6 examples

public class LinkedBlockingQueue
extends AbstractQueue
implements BlockingQueue, Serializable

An optionally-bounded {@linkplain BlockingQueue 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 {@link 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 {@link Collection} and {@link Iterator} interfaces.

This class is a member of the Java Collections Framework.

LinkedBlockingQueue

public LinkedBlockingQueue()

Creates a LinkedBlockingQueue with a capacity of {@link Integer#MAX_VALUE}.

LinkedBlockingQueue

public LinkedBlockingQueue(Collection c)

Creates a LinkedBlockingQueue with a capacity of {@link Integer#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

LinkedBlockingQueue

public LinkedBlockingQueue(int capacity)

Creates a LinkedBlockingQueue with the given (fixed) capacity.

Parameters:

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.

Overrides:

clear in class AbstractQueue

drainTo

public int drainTo(Collection c)

Parameters:

c

drainTo

public int drainTo(Collection c,
                   int maxElements)

Parameters:

c

maxElements

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 {@link 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:

iterator in class AbstractCollection

Returns:

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 {@link BlockingQueue#add add}, which can fail to insert an element only by throwing an exception.

Parameters:

e

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.

Parameters:

e

timeout

unit

Returns:

true if successful, or false if the specified waiting time elapses before space is available.

Throws:

InterruptedException - {@inheritDoc}

peek

public Object peek()

poll

public Object poll()

poll

public Object poll(long timeout,
                   TimeUnit unit)
            throws InterruptedException

Parameters:

timeout

unit

Throws:

InterruptedException

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.

Parameters:

e

Throws:

InterruptedException - {@inheritDoc}

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.

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:

remove in class AbstractCollection

Parameters:

o - element to be removed from this queue, if present

Returns:

true if this queue changed as a result of the call

size

public int size()

Returns the number of elements in this queue.

Overrides:

size in class AbstractCollection

Returns:

the number of elements in this queue

take

public Object take()
            throws InterruptedException

Throws:

InterruptedException

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:

toArray in class AbstractCollection

Returns:

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 {@link #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:

toArray in class AbstractCollection

Parameters:

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

Returns:

an array containing all of the elements in this queue

toString

public String toString()

Overrides:

toString in class AbstractCollection