jsr166y

类 LinkedTransferQueue<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractQueue<E>

jsr166y.LinkedTransferQueue<E>

类型参数:

E - the type of elements held in this collection

所有已实现的接口:

java.io.Serializable, java.lang.Iterable<E>, java.util.Collection<E>, java.util.concurrent.BlockingQueue<E>, java.util.Queue<E>, TransferQueue<E>

直接已知子类:

BoundedLinkedTransferQueue

public class LinkedTransferQueue<E>
extends java.util.AbstractQueue<E>
implements TransferQueue<E>, java.io.Serializable

An unbounded TransferQueue 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.

从以下版本开始:

1.7

作者:

Doug Lea

另请参阅:

序列化表格

嵌套类概要

嵌套类

限定符和类型	类和说明
(专用程序包) class	LinkedTransferQueue.Itr
(专用程序包) static class	LinkedTransferQueue.Node Queue nodes.

字段概要

字段

限定符和类型	字段和说明
private static int	ASYNC
private static int	CHAINED_SPINS The number of times to spin before blocking when a node is preceded by another node that is apparently spinning.
private static int	FRONT_SPINS The number of times to spin (with randomly interspersed calls to Thread.yield) on multiprocessor before blocking when a node is apparently the first waiter in the queue.
(专用程序包) LinkedTransferQueue.Node	head head of the queue; null until first enqueue
private static long	headOffset
private static boolean	MP True if on multiprocessor
private static int	NOW
private static long	serialVersionUID
(专用程序包) static int	SWEEP_THRESHOLD The maximum number of estimated removal failures (sweepVotes) to tolerate before sweeping through the queue unlinking cancelled nodes that were not unlinked upon initial removal.
private int	sweepVotes The number of apparent failures to unsplice removed nodes
private static long	sweepVotesOffset
private static int	SYNC
private LinkedTransferQueue.Node	tail tail of the queue; null until first append
private static long	tailOffset
private static int	TIMED
private static sun.misc.Unsafe	UNSAFE

构造器概要

构造器

构造器和说明
LinkedTransferQueue() Creates an initially empty LinkedTransferQueue.
LinkedTransferQueue(java.util.Collection<? extends E> c) Creates a LinkedTransferQueue initially containing the elements of the given collection, added in traversal order of the collection's iterator.

方法概要

方法

限定符和类型	方法和说明
boolean	add(E e) Inserts the specified element at the tail of this queue.
private E	awaitMatch(LinkedTransferQueue.Node s, LinkedTransferQueue.Node pred, E e, boolean timed, long nanos) Spins/yields/blocks until node s is matched or caller gives up.
private boolean	casHead(LinkedTransferQueue.Node cmp, LinkedTransferQueue.Node val)
private boolean	casSweepVotes(int cmp, int val)
(专用程序包) static <E> E	cast(java.lang.Object item)
private boolean	casTail(LinkedTransferQueue.Node cmp, LinkedTransferQueue.Node val)
private int	countOfMode(boolean data) Traverses and counts unmatched nodes of the given mode.
int	drainTo(java.util.Collection<? super E> c)
int	drainTo(java.util.Collection<? super E> c, int maxElements)
private boolean	findAndRemove(java.lang.Object e) Main implementation of remove(Object)
private E	firstDataItem() Returns the item in the first unmatched node with isData; or null if none.
private LinkedTransferQueue.Node	firstOfMode(boolean isData) Returns the first unmatched node of the given mode, or null if none.
(专用程序包) static sun.misc.Unsafe	getUnsafe() Returns a sun.misc.Unsafe.
int	getWaitingConsumerCount() Returns an estimate of the number of consumers waiting to receive elements via BlockingQueue.take() or timed poll.
boolean	hasWaitingConsumer() Returns true if there is at least one consumer waiting to receive an element via BlockingQueue.take() or timed poll.
boolean	isEmpty() Returns true if this queue contains no elements.
java.util.Iterator<E>	iterator() Returns an iterator over the elements in this queue in proper sequence, from head to tail.
(专用程序包) static long	objectFieldOffset(sun.misc.Unsafe UNSAFE, java.lang.String field, java.lang.Class<?> klazz)
boolean	offer(E e) Inserts the specified element at the tail of this queue.
boolean	offer(E e, long timeout, java.util.concurrent.TimeUnit unit) Inserts the specified element at the tail of this queue.
E	peek()
E	poll()
E	poll(long timeout, java.util.concurrent.TimeUnit unit)
void	put(E e) Inserts the specified element at the tail of this queue.
private void	readObject(java.io.ObjectInputStream s) Reconstitutes the Queue instance from a stream (that is, deserializes it).
int	remainingCapacity() Always returns Integer.MAX_VALUE because a LinkedTransferQueue is not capacity constrained.
boolean	remove(java.lang.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.
private static int	spinsFor(LinkedTransferQueue.Node pred, boolean haveData) Returns spin/yield value for a node with given predecessor and data mode.
(专用程序包) LinkedTransferQueue.Node	succ(LinkedTransferQueue.Node p) Returns the successor of p, or the head node if p.next has been linked to self, which will only be true if traversing with a stale pointer that is now off the list.
private void	sweep() Unlinks matched nodes encountered in a traversal from head.
E	take()
void	transfer(E e) Transfers the element to a consumer, waiting if necessary to do so.
private LinkedTransferQueue.Node	tryAppend(LinkedTransferQueue.Node s, boolean haveData) Tries to append node s as tail.
boolean	tryTransfer(E e) Transfers the element to a waiting consumer immediately, if possible.
boolean	tryTransfer(E e, long timeout, java.util.concurrent.TimeUnit unit) Transfers the element to a consumer if it is possible to do so before the timeout elapses.
(专用程序包) void	unsplice(LinkedTransferQueue.Node pred, LinkedTransferQueue.Node s) Unsplices (now or later) the given deleted/cancelled node with the given predecessor.
private void	writeObject(java.io.ObjectOutputStream s) Saves the state to a stream (that is, serializes it).
private E	xfer(E e, boolean haveData, int how, long nanos) Implements all queuing methods.

从类继承的方法 java.util.AbstractQueue

addAll, clear, element, remove

从类继承的方法 java.util.AbstractCollection

contains, containsAll, removeAll, retainAll, toArray, toArray, toString

从类继承的方法 java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

从接口继承的方法 java.util.concurrent.BlockingQueue

contains

从接口继承的方法 java.util.Queue

element, remove

从接口继承的方法 java.util.Collection

addAll, clear, containsAll, equals, hashCode, removeAll, retainAll, toArray, toArray

字段详细资料

serialVersionUID

private static final long serialVersionUID

另请参阅:

常量字段值

MP

private static final boolean MP

True if on multiprocessor

FRONT_SPINS

private static final int FRONT_SPINS

The number of times to spin (with randomly interspersed calls to Thread.yield) on multiprocessor before blocking when a node is apparently the first waiter in the queue. See above for explanation. Must be a power of two. The value is empirically derived -- it works pretty well across a variety of processors, numbers of CPUs, and OSes.

另请参阅:

常量字段值

CHAINED_SPINS

private static final int CHAINED_SPINS

The number of times to spin before blocking when a node is preceded by another node that is apparently spinning. Also serves as an increment to FRONT_SPINS on phase changes, and as base average frequency for yielding during spins. Must be a power of two.

另请参阅:

常量字段值

SWEEP_THRESHOLD

static final int SWEEP_THRESHOLD

The maximum number of estimated removal failures (sweepVotes) to tolerate before sweeping through the queue unlinking cancelled nodes that were not unlinked upon initial removal. See above for explanation. The value must be at least two to avoid useless sweeps when removing trailing nodes.

另请参阅:

常量字段值

head

transient volatile LinkedTransferQueue.Node head

head of the queue; null until first enqueue

tail

private transient volatile LinkedTransferQueue.Node tail

tail of the queue; null until first append

sweepVotes

private transient volatile int sweepVotes

The number of apparent failures to unsplice removed nodes

NOW

private static final int NOW

另请参阅:

常量字段值

ASYNC

private static final int ASYNC

另请参阅:

常量字段值

SYNC

private static final int SYNC

另请参阅:

常量字段值

TIMED

private static final int TIMED

另请参阅:

常量字段值

UNSAFE

private static final sun.misc.Unsafe UNSAFE

headOffset

private static final long headOffset

tailOffset

private static final long tailOffset

sweepVotesOffset

private static final long sweepVotesOffset

构造器详细资料

LinkedTransferQueue

public LinkedTransferQueue()

Creates an initially empty LinkedTransferQueue.

LinkedTransferQueue

public LinkedTransferQueue(java.util.Collection<? extends E> c)

Creates a LinkedTransferQueue initially containing the elements of the given collection, added in traversal order of the collection's iterator.

参数:

c - the collection of elements to initially contain

抛出:

java.lang.NullPointerException - if the specified collection or any of its elements are null

方法详细资料

casTail

private boolean casTail(LinkedTransferQueue.Node cmp,
              LinkedTransferQueue.Node val)

casHead

private boolean casHead(LinkedTransferQueue.Node cmp,
              LinkedTransferQueue.Node val)

casSweepVotes

private boolean casSweepVotes(int cmp,
                    int val)

cast

static <E> E cast(java.lang.Object item)

xfer

private E xfer(E e,
     boolean haveData,
     int how,
     long nanos)

Implements all queuing methods. See above for explanation.

参数:

e - the item or null for take

haveData - true if this is a put, else a take

how - NOW, ASYNC, SYNC, or TIMED

nanos - timeout in nanosecs, used only if mode is TIMED

返回:

an item if matched, else e

抛出:

java.lang.NullPointerException - if haveData mode but e is null

tryAppend

private LinkedTransferQueue.Node tryAppend(LinkedTransferQueue.Node s,
                                 boolean haveData)

Tries to append node s as tail.

参数:

s - the node to append

haveData - true if appending in data mode

返回:

null on failure due to losing race with append in different mode, else s's predecessor, or s itself if no predecessor

awaitMatch

private E awaitMatch(LinkedTransferQueue.Node s,
           LinkedTransferQueue.Node pred,
           E e,
           boolean timed,
           long nanos)

Spins/yields/blocks until node s is matched or caller gives up.

参数:

s - the waiting node

pred - the predecessor of s, or s itself if it has no predecessor, or null if unknown (the null case does not occur in any current calls but may in possible future extensions)

e - the comparison value for checking match

timed - if true, wait only until timeout elapses

nanos - timeout in nanosecs, used only if timed is true

返回:

matched item, or e if unmatched on interrupt or timeout

spinsFor

private static int spinsFor(LinkedTransferQueue.Node pred,
           boolean haveData)

Returns spin/yield value for a node with given predecessor and data mode. See above for explanation.

succ

final LinkedTransferQueue.Node succ(LinkedTransferQueue.Node p)

Returns the successor of p, or the head node if p.next has been linked to self, which will only be true if traversing with a stale pointer that is now off the list.

firstOfMode

private LinkedTransferQueue.Node firstOfMode(boolean isData)

Returns the first unmatched node of the given mode, or null if none. Used by methods isEmpty, hasWaitingConsumer.

firstDataItem

private E firstDataItem()

Returns the item in the first unmatched node with isData; or null if none. Used by peek.

countOfMode

private int countOfMode(boolean data)

Traverses and counts unmatched nodes of the given mode. Used by methods size and getWaitingConsumerCount.

unsplice

final void unsplice(LinkedTransferQueue.Node pred,
            LinkedTransferQueue.Node s)

Unsplices (now or later) the given deleted/cancelled node with the given predecessor.

参数:

pred - a node that was at one time known to be the predecessor of s, or null or s itself if s is/was at head

s - the node to be unspliced

sweep

private void sweep()

Unlinks matched nodes encountered in a traversal from head.

findAndRemove

private boolean findAndRemove(java.lang.Object e)

Main implementation of remove(Object)

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.

指定者:

put 在接口中 java.util.concurrent.BlockingQueue<E>

抛出:

java.lang.NullPointerException - if the specified element is null

offer

public boolean offer(E e,
            long timeout,
            java.util.concurrent.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.

指定者:

offer 在接口中 java.util.concurrent.BlockingQueue<E>

返回:

true (as specified by BlockingQueue.offer)

抛出:

java.lang.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.

指定者:

offer 在接口中 java.util.concurrent.BlockingQueue<E>

指定者:

offer 在接口中 java.util.Queue<E>

返回:

true (as specified by BlockingQueue.offer)

抛出:

java.lang.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.

指定者:

add 在接口中 java.util.Collection<E>

指定者:

add 在接口中 java.util.concurrent.BlockingQueue<E>

指定者:

add 在接口中 java.util.Queue<E>

覆盖:

add 在类中 java.util.AbstractQueue<E>

返回:

true (as specified by Collection.add(E))

抛出:

java.lang.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.

指定者:

tryTransfer 在接口中 TransferQueue<E>

参数:

e - the element to transfer

返回:

true if the element was transferred, else false

抛出:

java.lang.NullPointerException - if the specified element is null

transfer

public void transfer(E e)
              throws java.lang.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.

指定者:

transfer 在接口中 TransferQueue<E>

参数:

e - the element to transfer

抛出:

java.lang.NullPointerException - if the specified element is null

java.lang.InterruptedException - if interrupted while waiting, in which case the element is not left enqueued

tryTransfer

public boolean tryTransfer(E e,
                  long timeout,
                  java.util.concurrent.TimeUnit unit)
                    throws java.lang.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.

指定者:

tryTransfer 在接口中 TransferQueue<E>

参数:

e - the element to transfer

timeout - how long to wait before giving up, in units of unit

unit - a TimeUnit determining how to interpret the timeout parameter

返回:

true if successful, or false if the specified waiting time elapses before completion, in which case the element is not left enqueued

抛出:

java.lang.NullPointerException - if the specified element is null

java.lang.InterruptedException - if interrupted while waiting, in which case the element is not left enqueued

take

public E take()
       throws java.lang.InterruptedException

指定者:

take 在接口中 java.util.concurrent.BlockingQueue<E>

抛出:

java.lang.InterruptedException

poll

public E poll(long timeout,
     java.util.concurrent.TimeUnit unit)
       throws java.lang.InterruptedException

指定者:

poll 在接口中 java.util.concurrent.BlockingQueue<E>

抛出:

java.lang.InterruptedException

poll

public E poll()

指定者:

poll 在接口中 java.util.Queue<E>

drainTo

public int drainTo(java.util.Collection<? super E> c)

指定者:

drainTo 在接口中 java.util.concurrent.BlockingQueue<E>

抛出:

java.lang.NullPointerException

java.lang.IllegalArgumentException

drainTo

public int drainTo(java.util.Collection<? super E> c,
          int maxElements)

指定者:

drainTo 在接口中 java.util.concurrent.BlockingQueue<E>

抛出:

java.lang.NullPointerException

java.lang.IllegalArgumentException

iterator

public java.util.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.

指定者:

iterator 在接口中 java.lang.Iterable<E>

指定者:

iterator 在接口中 java.util.Collection<E>

指定者:

iterator 在类中 java.util.AbstractCollection<E>

返回:

an iterator over the elements in this queue in proper sequence

peek

public E peek()

指定者:

peek 在接口中 java.util.Queue<E>

isEmpty

public boolean isEmpty()

Returns true if this queue contains no elements.

指定者:

isEmpty 在接口中 java.util.Collection<E>

覆盖:

isEmpty 在类中 java.util.AbstractCollection<E>

返回:

true if this queue contains no elements

hasWaitingConsumer

public boolean hasWaitingConsumer()

从接口复制的说明: TransferQueue

Returns true if there is at least one consumer waiting to receive an element via BlockingQueue.take() or timed poll. The return value represents a momentary state of affairs.

指定者:

hasWaitingConsumer 在接口中 TransferQueue<E>

返回:

true if there is at least one waiting consumer

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.

指定者:

size 在接口中 java.util.Collection<E>

指定者:

size 在类中 java.util.AbstractCollection<E>

返回:

the number of elements in this queue

getWaitingConsumerCount

public int getWaitingConsumerCount()

从接口复制的说明: TransferQueue

Returns an estimate of the number of consumers waiting to receive elements via BlockingQueue.take() or timed poll. The return value is an approximation of a momentary state of affairs, that may be inaccurate if consumers have completed or given up waiting. The value may be useful for monitoring and heuristics, but not for synchronization control. Implementations of this method are likely to be noticeably slower than those for TransferQueue.hasWaitingConsumer().

指定者:

getWaitingConsumerCount 在接口中 TransferQueue<E>

返回:

the number of consumers waiting to receive elements

remove

public boolean remove(java.lang.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).

指定者:

remove 在接口中 java.util.Collection<E>

指定者:

remove 在接口中 java.util.concurrent.BlockingQueue<E>

覆盖:

remove 在类中 java.util.AbstractCollection<E>

参数:

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

返回:

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.

指定者:

remainingCapacity 在接口中 java.util.concurrent.BlockingQueue<E>

返回:

Integer.MAX_VALUE (as specified by BlockingQueue.remainingCapacity())

writeObject

private void writeObject(java.io.ObjectOutputStream s)
                  throws java.io.IOException

Saves the state to a stream (that is, serializes it).

参数:

s - the stream

抛出:

java.io.IOException

readObject

private void readObject(java.io.ObjectInputStream s)
                 throws java.io.IOException,
                        java.lang.ClassNotFoundException

Reconstitutes the Queue instance from a stream (that is, deserializes it).

参数:

s - the stream

抛出:

java.io.IOException

java.lang.ClassNotFoundException

objectFieldOffset

static long objectFieldOffset(sun.misc.Unsafe UNSAFE,
                     java.lang.String field,
                     java.lang.Class<?> klazz)

getUnsafe

static sun.misc.Unsafe getUnsafe()

Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. Replace with a simple call to Unsafe.getUnsafe when integrating into a jdk.

返回:

a sun.misc.Unsafe