程序包 java.util.concurrent

类 ConcurrentLinkedDeque<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.concurrent.ConcurrentLinkedDeque<E>

类型参数:

E - the type of elements held in this collection

所有已实现的接口:

Serializable, Iterable<E>, Collection<E>, Deque<E>, Queue<E>

public class ConcurrentLinkedDeque<E>
extends AbstractCollection<E>
implements Deque<E>, Serializable

An unbounded concurrent Deque based on linked nodes. Concurrent insertion, removal, and access operations execute safely across multiple threads. A ConcurrentLinkedDeque is an appropriate choice when many threads will share access to a common collection. Like most other concurrent collection implementations, this class does not permit the use of null elements.

Iterators and spliterators are weakly consistent.

Beware that, unlike in most collections, the size method is NOT a constant-time operation. Because of the asynchronous nature of these deques, determining the current number of elements requires a traversal of the elements, and so may report inaccurate results if this collection is modified during traversal. Additionally, the bulk operations addAll, removeAll, retainAll, containsAll, equals, and toArray are not guaranteed to be performed atomically. For example, an iterator operating concurrently with an addAll operation might view only some of the added elements.

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

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

This class is a member of the Java Collections Framework.

从以下版本开始:

1.7

另请参阅:

序列化表格

构造器概要

构造器

构造器	说明
ConcurrentLinkedDeque()	Constructs an empty deque.
ConcurrentLinkedDeque(Collection<? extends E> c)	Constructs a deque initially containing the elements of the given collection, added in traversal order of the collection's iterator.

方法概要

限定符和类型	方法	说明
boolean	add(E e)	Inserts the specified element at the tail of this deque.
boolean	addAll(Collection<? extends E> c)	Appends all of the elements in the specified collection to the end of this deque, in the order that they are returned by the specified collection's iterator.
void	addFirst(E e)	Inserts the specified element at the front of this deque.
void	addLast(E e)	Inserts the specified element at the end of this deque.
void	clear()	Removes all of the elements from this deque.
boolean	contains(Object o)	Returns true if this deque contains at least one element e such that o.equals(e).
Iterator<E>	descendingIterator()	Returns an iterator over the elements in this deque in reverse sequential order.
E	element()	Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque).
E	getFirst()	Retrieves, but does not remove, the first element of this deque.
E	getLast()	Retrieves, but does not remove, the last element of this deque.
boolean	isEmpty()	Returns true if this collection contains no elements.
Iterator<E>	iterator()	Returns an iterator over the elements in this deque in proper sequence.
boolean	offer(E e)	Inserts the specified element at the tail of this deque.
boolean	offerFirst(E e)	Inserts the specified element at the front of this deque.
boolean	offerLast(E e)	Inserts the specified element at the end of this deque.
E	peek()	Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque), or returns null if this deque is empty.
E	peekFirst()	Retrieves, but does not remove, the first element of this deque, or returns null if this deque is empty.
E	peekLast()	Retrieves, but does not remove, the last element of this deque, or returns null if this deque is empty.
E	poll()	Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), or returns null if this deque is empty.
E	pollFirst()	Retrieves and removes the first element of this deque, or returns null if this deque is empty.
E	pollLast()	Retrieves and removes the last element of this deque, or returns null if this deque is empty.
E	pop()	Pops an element from the stack represented by this deque.
void	push(E e)	Pushes an element onto the stack represented by this deque (in other words, at the head of this deque) if it is possible to do so immediately without violating capacity restrictions, throwing an IllegalStateException if no space is currently available.
E	remove()	Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque).
boolean	remove(Object o)	Removes the first element e such that o.equals(e), if such an element exists in this deque.
E	removeFirst()	Retrieves and removes the first element of this deque.
boolean	removeFirstOccurrence(Object o)	Removes the first element e such that o.equals(e), if such an element exists in this deque.
E	removeLast()	Retrieves and removes the last element of this deque.
boolean	removeLastOccurrence(Object o)	Removes the last element e such that o.equals(e), if such an element exists in this deque.
int	size()	Returns the number of elements in this deque.
Spliterator<E>	spliterator()	Returns a Spliterator over the elements in this deque.
Object[]	toArray()	Returns an array containing all of the elements in this deque, in proper sequence (from first to last element).
<T> T[]	toArray(T[] a)	Returns an array containing all of the elements in this deque, in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array.

从类继承的方法 java.util.AbstractCollection

containsAll, removeAll, retainAll, toString

从接口继承的方法 java.util.Collection

containsAll, equals, hashCode, parallelStream, removeAll, removeIf, retainAll, stream

从接口继承的方法 java.lang.Iterable

forEach

从类继承的方法 java.lang.Object

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

构造器详细资料

ConcurrentLinkedDeque

public ConcurrentLinkedDeque()

Constructs an empty deque.

ConcurrentLinkedDeque

public ConcurrentLinkedDeque(Collection<? extends E> c)

Constructs a deque 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:

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

方法详细资料

addFirst

public void addFirst(E e)

Inserts the specified element at the front of this deque. As the deque is unbounded, this method will never throw IllegalStateException.

指定者:

addFirst 在接口中 Deque<E>

参数:

e - the element to add

抛出:

NullPointerException - if the specified element is null

addLast

public void addLast(E e)

Inserts the specified element at the end of this deque. As the deque is unbounded, this method will never throw IllegalStateException.

This method is equivalent to add(E).

指定者:

addLast 在接口中 Deque<E>

参数:

e - the element to add

抛出:

NullPointerException - if the specified element is null

offerFirst

public boolean offerFirst(E e)

Inserts the specified element at the front of this deque. As the deque is unbounded, this method will never return false.

指定者:

offerFirst 在接口中 Deque<E>

参数:

e - the element to add

返回:

true (as specified by Deque#offerFirst)

抛出:

NullPointerException - if the specified element is null

offerLast

public boolean offerLast(E e)

Inserts the specified element at the end of this deque. As the deque is unbounded, this method will never return false.

This method is equivalent to add(E).

指定者:

offerLast 在接口中 Deque<E>

参数:

e - the element to add

返回:

true (as specified by Deque#offerLast)

抛出:

NullPointerException - if the specified element is null

peekFirst

public E peekFirst()

从接口复制的说明: Deque

Retrieves, but does not remove, the first element of this deque, or returns null if this deque is empty.

指定者:

peekFirst 在接口中 Deque<E>

返回:

the head of this deque, or null if this deque is empty

peekLast

public E peekLast()

从接口复制的说明: Deque

Retrieves, but does not remove, the last element of this deque, or returns null if this deque is empty.

指定者:

peekLast 在接口中 Deque<E>

返回:

the tail of this deque, or null if this deque is empty

getFirst

public E getFirst()

从接口复制的说明: Deque

Retrieves, but does not remove, the first element of this deque. This method differs from peekFirst only in that it throws an exception if this deque is empty.

指定者:

getFirst 在接口中 Deque<E>

返回:

the head of this deque

抛出:

NoSuchElementException - if this deque is empty

getLast

public E getLast()

从接口复制的说明: Deque

Retrieves, but does not remove, the last element of this deque. This method differs from peekLast only in that it throws an exception if this deque is empty.

指定者:

getLast 在接口中 Deque<E>

返回:

the tail of this deque

抛出:

NoSuchElementException - if this deque is empty

pollFirst

public E pollFirst()

从接口复制的说明: Deque

Retrieves and removes the first element of this deque, or returns null if this deque is empty.

指定者:

pollFirst 在接口中 Deque<E>

返回:

the head of this deque, or null if this deque is empty

pollLast

public E pollLast()

从接口复制的说明: Deque

Retrieves and removes the last element of this deque, or returns null if this deque is empty.

指定者:

pollLast 在接口中 Deque<E>

返回:

the tail of this deque, or null if this deque is empty

removeFirst

public E removeFirst()

从接口复制的说明: Deque

Retrieves and removes the first element of this deque. This method differs from pollFirst only in that it throws an exception if this deque is empty.

指定者:

removeFirst 在接口中 Deque<E>

返回:

the head of this deque

抛出:

NoSuchElementException - if this deque is empty

removeLast

public E removeLast()

从接口复制的说明: Deque

Retrieves and removes the last element of this deque. This method differs from pollLast only in that it throws an exception if this deque is empty.

指定者:

removeLast 在接口中 Deque<E>

返回:

the tail of this deque

抛出:

NoSuchElementException - if this deque is empty

offer

public boolean offer(E e)

Inserts the specified element at the tail of this deque. As the deque is unbounded, this method will never return false.

指定者:

offer 在接口中 Deque<E>

指定者:

offer 在接口中 Queue<E>

参数:

e - the element to add

返回:

true (as specified by Queue#offer)

抛出:

NullPointerException - if the specified element is null

add

public boolean add(E e)

Inserts the specified element at the tail of this deque. As the deque is unbounded, this method will never throw IllegalStateException or return false.

指定者:

add 在接口中 Collection<E>

指定者:

add 在接口中 Deque<E>

指定者:

add 在接口中 Queue<E>

覆盖:

add 在类中 AbstractCollection<E>

参数:

e - element whose presence in this collection is to be ensured

返回:

true (as specified by Collection#add)

抛出:

NullPointerException - if the specified element is null

poll

public E poll()

从接口复制的说明: Deque

Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), or returns null if this deque is empty.

This method is equivalent to Deque.pollFirst().

指定者:

poll 在接口中 Deque<E>

指定者:

poll 在接口中 Queue<E>

返回:

the first element of this deque, or null if this deque is empty

peek

public E peek()

从接口复制的说明: Deque

Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque), or returns null if this deque is empty.

This method is equivalent to Deque.peekFirst().

指定者:

peek 在接口中 Deque<E>

指定者:

peek 在接口中 Queue<E>

返回:

the head of the queue represented by this deque, or null if this deque is empty

remove

public E remove()

从接口复制的说明: Deque

Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque). This method differs from poll only in that it throws an exception if this deque is empty.

This method is equivalent to Deque.removeFirst().

指定者:

remove 在接口中 Deque<E>

指定者:

remove 在接口中 Queue<E>

返回:

the head of the queue represented by this deque

抛出:

NoSuchElementException - if this deque is empty

pop

public E pop()

从接口复制的说明: Deque

Pops an element from the stack represented by this deque. In other words, removes and returns the first element of this deque.

This method is equivalent to Deque.removeFirst().

指定者:

pop 在接口中 Deque<E>

返回:

the element at the front of this deque (which is the top of the stack represented by this deque)

抛出:

NoSuchElementException - if this deque is empty

element

public E element()

从接口复制的说明: Deque

Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque). This method differs from peek only in that it throws an exception if this deque is empty.

This method is equivalent to Deque.getFirst().

指定者:

element 在接口中 Deque<E>

指定者:

element 在接口中 Queue<E>

返回:

the head of the queue represented by this deque

抛出:

NoSuchElementException - if this deque is empty

push

public void push(E e)

从接口复制的说明: Deque

Pushes an element onto the stack represented by this deque (in other words, at the head of this deque) if it is possible to do so immediately without violating capacity restrictions, throwing an IllegalStateException if no space is currently available.

This method is equivalent to Deque.addFirst(E).

指定者:

push 在接口中 Deque<E>

参数:

e - the element to push

抛出:

NullPointerException - if the specified element is null and this deque does not permit null elements

removeFirstOccurrence

public boolean removeFirstOccurrence(Object o)

Removes the first element e such that o.equals(e), if such an element exists in this deque. If the deque does not contain the element, it is unchanged.

指定者:

removeFirstOccurrence 在接口中 Deque<E>

参数:

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

返回:

true if the deque contained the specified element

抛出:

NullPointerException - if the specified element is null

removeLastOccurrence

public boolean removeLastOccurrence(Object o)

Removes the last element e such that o.equals(e), if such an element exists in this deque. If the deque does not contain the element, it is unchanged.

指定者:

removeLastOccurrence 在接口中 Deque<E>

参数:

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

返回:

true if the deque contained the specified element

抛出:

NullPointerException - if the specified element is null

contains

public boolean contains(Object o)

Returns true if this deque contains at least one element e such that o.equals(e).

指定者:

contains 在接口中 Collection<E>

指定者:

contains 在接口中 Deque<E>

覆盖:

contains 在类中 AbstractCollection<E>

参数:

o - element whose presence in this deque is to be tested

返回:

true if this deque contains the specified element

isEmpty

public boolean isEmpty()

Returns true if this collection contains no elements.

指定者:

isEmpty 在接口中 Collection<E>

覆盖:

isEmpty 在类中 AbstractCollection<E>

返回:

true if this collection contains no elements

size

public int size()

Returns the number of elements in this deque. If this deque contains more than Integer.MAX_VALUE elements, it 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 deques, determining the current number of elements requires traversing them all to count them. Additionally, it is possible for the size to change during execution of this method, in which case the returned result will be inaccurate. Thus, this method is typically not very useful in concurrent applications.

指定者:

size 在接口中 Collection<E>

指定者:

size 在接口中 Deque<E>

指定者:

size 在类中 AbstractCollection<E>

返回:

the number of elements in this deque

remove

public boolean remove(Object o)

Removes the first element e such that o.equals(e), if such an element exists in this deque. If the deque does not contain the element, it is unchanged.

指定者:

remove 在接口中 Collection<E>

指定者:

remove 在接口中 Deque<E>

覆盖:

remove 在类中 AbstractCollection<E>

参数:

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

返回:

true if the deque contained the specified element

抛出:

NullPointerException - if the specified element is null

addAll

public boolean addAll(Collection<? extends E> c)

Appends all of the elements in the specified collection to the end of this deque, in the order that they are returned by the specified collection's iterator. Attempts to addAll of a deque to itself result in IllegalArgumentException.

指定者:

addAll 在接口中 Collection<E>

覆盖:

addAll 在类中 AbstractCollection<E>

参数:

c - the elements to be inserted into this deque

返回:

true if this deque changed as a result of the call

抛出:

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

IllegalArgumentException - if the collection is this deque

另请参阅:

AbstractCollection.add(Object)

clear

public void clear()

Removes all of the elements from this deque.

指定者:

clear 在接口中 Collection<E>

覆盖:

clear 在类中 AbstractCollection<E>

toArray

public Object[] toArray()

Returns an array containing all of the elements in this deque, in proper sequence (from first to last element).

The returned array will be "safe" in that no references to it are maintained by this deque. (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.

指定者:

toArray 在接口中 Collection<E>

覆盖:

toArray 在类中 AbstractCollection<E>

返回:

an array containing all of the elements in this deque

toArray

public <T> T[] toArray(T[] a)

Returns an array containing all of the elements in this deque, in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array. If the deque 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 deque.

If this deque fits in the specified array with room to spare (i.e., the array has more elements than this deque), the element in the array immediately following the end of the deque 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 deque known to contain only strings. The following code can be used to dump the deque 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().

指定者:

toArray 在接口中 Collection<E>

覆盖:

toArray 在类中 AbstractCollection<E>

类型参数:

T - the runtime type of the array to contain the collection

参数:

a - the array into which the elements of the deque are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose

返回:

an array containing all of the elements in this deque

抛出:

ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this deque

NullPointerException - if the specified array is null

iterator

public Iterator<E> iterator()

Returns an iterator over the elements in this deque in proper sequence. The elements will be returned in order from first (head) to last (tail).

The returned iterator is weakly consistent.

指定者:

iterator 在接口中 Collection<E>

指定者:

iterator 在接口中 Deque<E>

指定者:

iterator 在接口中 Iterable<E>

指定者:

iterator 在类中 AbstractCollection<E>

返回:

an iterator over the elements in this deque in proper sequence

descendingIterator

public Iterator<E> descendingIterator()

Returns an iterator over the elements in this deque in reverse sequential order. The elements will be returned in order from last (tail) to first (head).

The returned iterator is weakly consistent.

指定者:

descendingIterator 在接口中 Deque<E>

返回:

an iterator over the elements in this deque in reverse order

spliterator

public Spliterator<E> spliterator()

Returns a Spliterator over the elements in this deque.

The returned spliterator is weakly consistent.

The Spliterator reports Spliterator#CONCURRENT, Spliterator#ORDERED, and Spliterator#NONNULL.

指定者:

spliterator 在接口中 Collection<E>

指定者:

spliterator 在接口中 Iterable<E>

返回:

a Spliterator over the elements in this deque

从以下版本开始:

1.8