程序包 java.util

类 ArrayDeque<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.ArrayDeque<E>

类型参数:

E - the type of elements held in this collection

所有已实现的接口:

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

public class ArrayDeque<E>
extends AbstractCollection<E>
implements Deque<E>, Cloneable, Serializable

Resizable-array implementation of the Deque interface. Array deques have no capacity restrictions; they grow as necessary to support usage. They are not thread-safe; in the absence of external synchronization, they do not support concurrent access by multiple threads. Null elements are prohibited. This class is likely to be faster than Stack when used as a stack, and faster than LinkedList when used as a queue.

Most ArrayDeque operations run in amortized constant time. Exceptions include remove, removeFirstOccurrence, removeLastOccurrence, contains, iterator.remove(), and the bulk operations, all of which run in linear time.

The iterators returned by this class's iterator method are fail-fast: If the deque is modified at any time after the iterator is created, in any way except through the iterator's own remove method, the iterator will generally throw a ConcurrentModificationException. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.

Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast iterators throw ConcurrentModificationException on a best-effort basis. Therefore, it would be wrong to write a program that depended on this exception for its correctness: the fail-fast behavior of iterators should be used only to detect bugs.

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.

从以下版本开始:

1.6

另请参阅:

序列化表格

构造器概要

构造器

构造器	说明
ArrayDeque()	Constructs an empty array deque with an initial capacity sufficient to hold 16 elements.
ArrayDeque(int numElements)	Constructs an empty array deque with an initial capacity sufficient to hold the specified number of elements.
ArrayDeque(Collection<? extends E> c)	Constructs a deque containing the elements of the specified collection, in the order they are returned by 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 end of this deque.
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.
ArrayDeque<E>	clone()	Returns a copy of this deque.
boolean	contains(Object o)	Returns true if this deque contains the specified element.
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.
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 deque contains no elements.
Iterator<E>	iterator()	Returns an iterator over the elements in this deque.
boolean	offer(E e)	Inserts the specified element at the end 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, 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.
E	remove()	Retrieves and removes the head of the queue represented by this deque.
boolean	remove(Object o)	Removes a single instance of the specified element from this deque.
E	removeFirst()	Retrieves and removes the first element of this deque.
boolean	removeFirstOccurrence(Object o)	Removes the first occurrence of the specified element in this deque (when traversing the deque from head to tail).
E	removeLast()	Retrieves and removes the last element of this deque.
boolean	removeLastOccurrence(Object o)	Removes the last occurrence of the specified element in this deque (when traversing the deque from head to tail).
int	size()	Returns the number of elements in this deque.
Spliterator<E>	spliterator()	Creates a late-binding and fail-fast 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

addAll, containsAll, removeAll, retainAll, toString

从接口继承的方法 java.util.Collection

addAll, 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

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

构造器详细资料

ArrayDeque

public ArrayDeque()

Constructs an empty array deque with an initial capacity sufficient to hold 16 elements.

ArrayDeque

public ArrayDeque(int numElements)

Constructs an empty array deque with an initial capacity sufficient to hold the specified number of elements.

参数:

numElements - lower bound on initial capacity of the deque

ArrayDeque

public ArrayDeque(Collection<? extends E> c)

Constructs a deque containing the elements of the specified collection, in the order they are returned by the collection's iterator. (The first element returned by the collection's iterator becomes the first element, or front of the deque.)

参数:

c - the collection whose elements are to be placed into the deque

抛出:

NullPointerException - if the specified collection is null

方法详细资料

addFirst

public void addFirst(E e)

Inserts the specified element at the front of this deque.

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.

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.

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.

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

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

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

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

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

removeFirstOccurrence

public boolean removeFirstOccurrence(Object o)

Removes the first occurrence of the specified element in this deque (when traversing the deque from head to tail). If the deque does not contain the element, it is unchanged. More formally, removes the first element e such that o.equals(e) (if such an element exists). Returns true if this deque contained the specified element (or equivalently, if this deque changed as a result of the call).

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

removeLastOccurrence

public boolean removeLastOccurrence(Object o)

Removes the last occurrence of the specified element in this deque (when traversing the deque from head to tail). If the deque does not contain the element, it is unchanged. More formally, removes the last element e such that o.equals(e) (if such an element exists). Returns true if this deque contained the specified element (or equivalently, if this deque changed as a result of the call).

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

add

public boolean add(E e)

Inserts the specified element at the end of this deque.

This method is equivalent to addLast(E).

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 - the element to add

返回:

true (as specified by Collection#add)

抛出:

NullPointerException - if the specified element is null

offer

public boolean offer(E e)

Inserts the specified element at the end of this deque.

This method is equivalent to offerLast(E).

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

remove

public E remove()

Retrieves and removes the head of the queue represented by this deque. This method differs from poll only in that it throws an exception if this deque is empty.

This method is equivalent to 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

poll

public 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.

This method is equivalent to pollFirst().

指定者:

poll 在接口中 Deque<E>

指定者:

poll 在接口中 Queue<E>

返回:

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

element

public E element()

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

This method is equivalent to 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

peek

public E peek()

Retrieves, but does not remove, the head of the queue represented by this deque, or returns null if this deque is empty.

This method is equivalent to 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

push

public void push(E e)

Pushes an element onto the stack represented by this deque. In other words, inserts the element at the front of this deque.

This method is equivalent to 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

pop

public E pop()

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 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

size

public int size()

Returns the number of elements in this deque.

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

isEmpty

public boolean isEmpty()

Returns true if this deque 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 deque contains no elements

iterator

public Iterator<E> iterator()

Returns an iterator over the elements in this deque. The elements will be ordered from first (head) to last (tail). This is the same order that elements would be dequeued (via successive calls to remove() or popped (via successive calls to pop()).

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

descendingIterator

public Iterator<E> descendingIterator()

从接口复制的说明: Deque

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).

指定者:

descendingIterator 在接口中 Deque<E>

返回:

an iterator over the elements in this deque in reverse sequence

contains

public boolean contains(Object o)

Returns true if this deque contains the specified element. More formally, returns true if and only 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 - object to be checked for containment in this deque

返回:

true if this deque contains the specified element

remove

public boolean remove(Object o)

Removes a single instance of the specified element from this deque. If the deque does not contain the element, it is unchanged. More formally, removes the first element e such that o.equals(e) (if such an element exists). Returns true if this deque contained the specified element (or equivalently, if this deque changed as a result of the call).

This method is equivalent to removeFirstOccurrence(java.lang.Object).

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 this deque contained the specified element

clear

public void clear()

Removes all of the elements from this deque. The deque will be empty after this call returns.

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

clone

public ArrayDeque<E> clone()

Returns a copy of this deque.

覆盖:

clone 在类中 Object

返回:

a copy of this deque

另请参阅:

Cloneable

spliterator

public Spliterator<E> spliterator()

Creates a late-binding and fail-fast Spliterator over the elements in this deque.

The Spliterator reports Spliterator#SIZED, Spliterator#SUBSIZED, Spliterator#ORDERED, and Spliterator#NONNULL. Overriding implementations should document the reporting of additional characteristic values.

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