org.jboss.netty.util.internal
Class LinkedTransferQueue<E>

java.lang.Object
  extended by java.util.AbstractCollection<E>
      extended by java.util.AbstractQueue<E>
          extended by org.jboss.netty.util.internal.LinkedTransferQueue<E>
Type Parameters:
E - the type of elements held in this collection
All Implemented Interfaces:
Serializable, Iterable<E>, Collection<E>, BlockingQueue<E>, Queue<E>

public class LinkedTransferQueue<E>
extends AbstractQueue<E>
implements BlockingQueue<E>, Serializable

An unbounded BlockingQueue based on linked nodes. This queue orders elements FIFO (first-in-first-out) with respect to any given producer. The head of the queue is that element that has been on the queue the longest time for some producer. The tail of the queue is that element that has been on the queue the shortest time for some producer.

Beware that, unlike in most collections, the size method is NOT a constant-time operation. Because of the asynchronous nature of these queues, determining the current number of elements requires a traversal of the elements.

This class and its iterator implement all of the optional methods of the Collection and Iterator interfaces.

Memory consistency effects: As with other concurrent collections, actions in a thread prior to placing an object into a LinkedTransferQueue happen-before actions subsequent to the access or removal of that element from the LinkedTransferQueue in another thread.

This class is a member of the Java Collections Framework.

Version:
$Rev: 2373 $, $Date: 2010-10-20 20:33:23 +0900 (Wed, 20 Oct 2010) $ (Upstream: 1.79)
Author:
The Netty Project, Doug Lea, Trustin Lee
See Also:
Serialized Form

Constructor Summary
LinkedTransferQueue()
          Creates an initially empty LinkedTransferQueue.
LinkedTransferQueue(Collection<? extends E> c)
          Creates a LinkedTransferQueue initially containing the elements of the given collection, added in traversal order of the collection's iterator.
 
Method Summary
 boolean add(E e)
          Inserts the specified element at the tail of this queue.
 int drainTo(Collection<? super E> c)
           
 int drainTo(Collection<? super E> c, int maxElements)
           
 int getWaitingConsumerCount()
           
 boolean hasWaitingConsumer()
           
 boolean isEmpty()
          Returns true if this queue contains no elements.
 Iterator<E> iterator()
          Returns an iterator over the elements in this queue in proper sequence, from head to tail.
 boolean offer(E e)
          Inserts the specified element at the tail of this queue.
 boolean offer(E e, long timeout, TimeUnit unit)
          Inserts the specified element at the tail of this queue.
 E peek()
           
 E poll()
           
 E poll(long timeout, TimeUnit unit)
           
 void put(E e)
          Inserts the specified element at the tail of this queue.
 int remainingCapacity()
          Always returns Integer.MAX_VALUE because a LinkedTransferQueue is not capacity constrained.
 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()
           
 void transfer(E e)
          Transfers the element to a consumer, waiting if necessary to do so.
 boolean tryTransfer(E e)
          Transfers the element to a waiting consumer immediately, if possible.
 boolean tryTransfer(E e, long timeout, TimeUnit unit)
          Transfers the element to a consumer if it is possible to do so before the timeout elapses.
 
Methods inherited from class java.util.AbstractQueue
addAll, clear, element, remove
 
Methods inherited from class java.util.AbstractCollection
contains, containsAll, removeAll, retainAll, toArray, toArray, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface java.util.concurrent.BlockingQueue
contains
 
Methods inherited from interface java.util.Queue
element, remove
 
Methods inherited from interface java.util.Collection
addAll, clear, containsAll, equals, hashCode, removeAll, retainAll, toArray, toArray
 

Constructor Detail

LinkedTransferQueue

public LinkedTransferQueue()
Creates an initially empty LinkedTransferQueue.


LinkedTransferQueue

public LinkedTransferQueue(Collection<? extends E> c)
Creates a LinkedTransferQueue 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 - if the specified collection or any of its elements are null
Method Detail

put

public void put(E e)
Inserts the specified element at the tail of this queue. As the queue is unbounded, this method will never block.

Specified by:
put in interface BlockingQueue<E>
Throws:
NullPointerException - if the specified element is null

offer

public boolean offer(E e,
                     long timeout,
                     TimeUnit unit)
Inserts the specified element at the tail of this queue. As the queue is unbounded, this method will never block or return false.

Specified by:
offer in interface BlockingQueue<E>
Returns:
true (as specified by BlockingQueue.offer)
Throws:
NullPointerException - if the specified element is null

offer

public boolean offer(E e)
Inserts the specified element at the tail of this queue. As the queue is unbounded, this method will never return false.

Specified by:
offer in interface BlockingQueue<E>
Specified by:
offer in interface Queue<E>
Returns:
true (as specified by BlockingQueue.offer)
Throws:
NullPointerException - if the specified element is null

add

public boolean add(E e)
Inserts the specified element at the tail of this queue. As the queue is unbounded, this method will never throw IllegalStateException or return false.

Specified by:
add in interface Collection<E>
Specified by:
add in interface BlockingQueue<E>
Specified by:
add in interface Queue<E>
Overrides:
add in class AbstractQueue<E>
Returns:
true (as specified by Collection.add(E))
Throws:
NullPointerException - if the specified element is null

tryTransfer

public boolean tryTransfer(E e)
Transfers the element to a waiting consumer immediately, if possible.

More precisely, transfers the specified element immediately if there exists a consumer already waiting to receive it (in take() or timed poll), otherwise returning false without enqueuing the element.

Throws:
NullPointerException - if the specified element is null

transfer

public void transfer(E e)
              throws InterruptedException
Transfers the element to a consumer, waiting if necessary to do so.

More precisely, transfers the specified element immediately if there exists a consumer already waiting to receive it (in take() or timed poll), else inserts the specified element at the tail of this queue and waits until the element is received by a consumer.

Throws:
NullPointerException - if the specified element is null
InterruptedException

tryTransfer

public boolean tryTransfer(E e,
                           long timeout,
                           TimeUnit unit)
                    throws InterruptedException
Transfers the element to a consumer if it is possible to do so before the timeout elapses.

More precisely, transfers the specified element immediately if there exists a consumer already waiting to receive it (in take() or timed poll), else inserts the specified element at the tail of this queue and waits until the element is received by a consumer, returning false if the specified wait time elapses before the element can be transferred.

Throws:
NullPointerException - if the specified element is null
InterruptedException

take

public E take()
       throws InterruptedException
Specified by:
take in interface BlockingQueue<E>
Throws:
InterruptedException

poll

public E poll(long timeout,
              TimeUnit unit)
       throws InterruptedException
Specified by:
poll in interface BlockingQueue<E>
Throws:
InterruptedException

poll

public E poll()
Specified by:
poll in interface Queue<E>

drainTo

public int drainTo(Collection<? super E> c)
Specified by:
drainTo in interface BlockingQueue<E>
Throws:
NullPointerException
IllegalArgumentException

drainTo

public int drainTo(Collection<? super E> c,
                   int maxElements)
Specified by:
drainTo in interface BlockingQueue<E>
Throws:
NullPointerException
IllegalArgumentException

iterator

public Iterator<E> iterator()
Returns an iterator over the elements in this queue in proper sequence, from head to tail.

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 in interface Iterable<E>
Specified by:
iterator in interface Collection<E>
Specified by:
iterator in class AbstractCollection<E>
Returns:
an iterator over the elements in this queue in proper sequence

peek

public E peek()
Specified by:
peek in interface Queue<E>

isEmpty

public boolean isEmpty()
Returns true if this queue contains no elements.

Specified by:
isEmpty in interface Collection<E>
Overrides:
isEmpty in class AbstractCollection<E>
Returns:
true if this queue contains no elements

hasWaitingConsumer

public boolean hasWaitingConsumer()

size

public int size()
Returns the number of elements in this queue. If this queue contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.

Beware that, unlike in most collections, this method is NOT a constant-time operation. Because of the asynchronous nature of these queues, determining the current number of elements requires an O(n) traversal.

Specified by:
size in interface Collection<E>
Specified by:
size in class AbstractCollection<E>
Returns:
the number of elements in this queue

getWaitingConsumerCount

public int getWaitingConsumerCount()

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).

Specified by:
remove in interface Collection<E>
Specified by:
remove in interface BlockingQueue<E>
Overrides:
remove in class AbstractCollection<E>
Parameters:
o - element to be removed from this queue, if present
Returns:
true if this queue changed as a result of the call

remainingCapacity

public int remainingCapacity()
Always returns Integer.MAX_VALUE because a LinkedTransferQueue is not capacity constrained.

Specified by:
remainingCapacity in interface BlockingQueue<E>
Returns:
Integer.MAX_VALUE (as specified by BlockingQueue.remainingCapacity())


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