java.util

Class ArrayDeque<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.ArrayDeque<E>

Type Parameters:

E - the type of elements in this collection

All Implemented Interfaces:

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

public class ArrayDeque<E>
extends AbstractCollection<E>
implements Deque<E>

An implementation of Deque, backed by an array. ArrayDeques have no size limit, can not contain null element, and they are not thread-safe. All optional operations are supported, and the elements can be any objects.

Since:

1.6

Constructor Summary

Constructors

Constructor and Description
ArrayDeque() Constructs a new empty instance of ArrayDeque big enough for 16 elements.
ArrayDeque(Collection<? extends E> c) Constructs a new instance of ArrayDeque containing the elements of the specified collection, with the order returned by the collection's iterator.
ArrayDeque(int minSize) Constructs a new empty instance of ArrayDeque big enough for specified number of elements.

Method Summary

Modifier and Type	Method and Description
boolean	add(E e) Inserts the element to the tail of the deque.
void	addFirst(E e) Inserts an element at the head of this deque if it dose not violate size limit immediately.
void	addLast(E e) Inserts an element at the tail of this deque if it dose not violate size limit immediately.
void	clear() Empty the deque.
boolean	contains(Object obj) Returns true if the specified element is in the deque.
Iterator<E>	descendingIterator() Returns the iterator in reverse order, from tail to head.
E	element() Gets but does not remove the head element of this deque.
E	getFirst() Gets but not removes the head element of this deque.
E	getLast() Gets but not removes the tail element of this deque.
boolean	isEmpty() Returns true if the deque has no elements.
Iterator<E>	iterator() Returns the iterator of the deque.
boolean	offer(E e) Inserts the element at the tail of the deque.
boolean	offerFirst(E e) Inserts an element at the head of this deque unless it would violate size limit.
boolean	offerLast(E e) Inserts an element at the tail of this deque unless it would violate size limit.
E	peek() Gets but not removes the head element of this deque.
E	peekFirst() Gets but not removes the head element of this deque.
E	peekLast() Gets but not removes the tail element of this deque.
E	poll() Gets and removes the head element of this deque.
E	pollFirst() Gets and removes the head element of this deque.
E	pollLast() Gets and removes the tail element of this deque.
E	pop() Pops the head element of the deque, just same as removeFirst().
void	push(E e) Pushes the element to the deque(at the head of the deque), just same as addFirst(E).
E	remove() Gets and removes the head element of this deque.
boolean	remove(Object obj) Removes the first equivalent element of the specified object.
E	removeFirst() Gets and removes the head element of this deque.
boolean	removeFirstOccurrence(Object obj) Removes the first equivalent element of the specified object.
E	removeLast() Gets and removes the tail element of this deque.
boolean	removeLastOccurrence(Object obj) Removes the last equivalent element of the specified object.
int	size() Returns the size of the deque.

Methods inherited from class java.util.AbstractCollection

addAll, containsAll, removeAll, retainAll, toArray, toArray, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Collection

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

Constructor Detail

ArrayDeque

public ArrayDeque()

Constructs a new empty instance of ArrayDeque big enough for 16 elements.

ArrayDeque

public ArrayDeque(int minSize)

Constructs a new empty instance of ArrayDeque big enough for specified number of elements.

Parameters:

minSize - the smallest size of the ArrayDeque

ArrayDeque

public ArrayDeque(Collection<? extends E> c)

Constructs a new instance of ArrayDeque containing the elements of the specified collection, with the order returned by the collection's iterator.

Parameters:

c - the source of the elements

Throws:

NullPointerException - if the collection is null

Method Detail

addFirst

public void addFirst(E e)

Inserts an element at the head of this deque if it dose not violate size limit immediately. It is better to use offerFirst(E) if a deque is size-limited.

Specified by:

addFirst in interface Deque<E>

Parameters:

e - the element

Throws:

NullPointerException - if the element is null

See Also:

Deque.addFirst(java.lang.Object)

addLast

public void addLast(E e)

Inserts an element at the tail of this deque if it dose not violate size limit immediately. It is better to use offerLast(E) if a deque is size-limited.

Specified by:

addLast in interface Deque<E>

Parameters:

e - the element

Throws:

NullPointerException - if the element is null

See Also:

Deque.addLast(java.lang.Object)

offerFirst

public boolean offerFirst(E e)

Inserts an element at the head of this deque unless it would violate size limit. It is better than the addFirst(E) method in a size-limited deque, because the latter one may fail to add the element only by throwing an exception.

Specified by:

offerFirst in interface Deque<E>

Parameters:

e - the element

Returns:

true

Throws:

NullPointerException - if the element is null

See Also:

Deque.offerFirst(java.lang.Object)

offerLast

public boolean offerLast(E e)

Inserts an element at the tail of this deque unless it would violate size limit. It is better than the addLast(E) method in a size-limited deque, because the latter one may fail to add the element only by throwing an exception.

Specified by:

offerLast in interface Deque<E>

Parameters:

e - the element

Returns:

true if the operation succeeds or false if it fails

Throws:

NullPointerException - if the element is null

See Also:

Deque.offerLast(java.lang.Object)

offer

public boolean offer(E e)

Inserts the element at the tail of the deque.

Specified by:

offer in interface Queue<E>

Parameters:

e - the element

Returns:

true if the operation succeeds or false if it fails.

Throws:

NullPointerException - if the element is null

See Also:

Queue.offer(java.lang.Object)

add

public boolean add(E e)

Inserts the element to the tail of the deque.

Specified by:

add in interface Collection<E>

Overrides:

add in class AbstractCollection<E>

Parameters:

e - the element

Returns:

true

See Also:

AbstractCollection.add(java.lang.Object)

push

public void push(E e)

Pushes the element to the deque(at the head of the deque), just same as addFirst(E).

Specified by:

push in interface Deque<E>

Parameters:

e - the element to push

Throws:

NullPointerException - if the element is null

See Also:

Deque.push(java.lang.Object)

removeFirst

public E removeFirst()

Gets and removes the head element of this deque. This method throws an exception if the deque is empty.

Specified by:

removeFirst in interface Deque<E>

Returns:

the head element

Throws:

NoSuchElementException - if the deque is empty

See Also:

Deque.removeFirst()

remove

public E remove()

Gets and removes the head element of this deque. This method throws an exception if the deque is empty.

Specified by:

remove in interface Queue<E>

Returns:

the head element

Throws:

NoSuchElementException - if the deque is empty

See Also:

Queue.remove()

pop

public E pop()

Pops the head element of the deque, just same as removeFirst().

Specified by:

pop in interface Deque<E>

Returns:

the head element

Throws:

NoSuchElementException - if the deque is empty

See Also:

Deque.pop()

removeLast

public E removeLast()

Gets and removes the tail element of this deque. This method throws an exception if the deque is empty.

Specified by:

removeLast in interface Deque<E>

Returns:

the tail element

Throws:

NoSuchElementException - if the deque is empty

See Also:

Deque.removeLast()

pollFirst

public E pollFirst()

Gets and removes the head element of this deque. This method returns null if the deque is empty.

Specified by:

pollFirst in interface Deque<E>

Returns:

the head element or null if the deque is empty

See Also:

Deque.pollFirst()

poll

public E poll()

Gets and removes the head element of this deque. This method returns null if the deque is empty.

Specified by:

poll in interface Queue<E>

Returns:

the head element or null if the deque is empty

See Also:

Queue.poll()

pollLast

public E pollLast()

Gets and removes the tail element of this deque. This method returns null if the deque is empty.

Specified by:

pollLast in interface Deque<E>

Returns:

the tail element or null if the deque is empty

See Also:

Deque.pollLast()

getFirst

public E getFirst()

Gets but not removes the head element of this deque. This method throws an exception if the deque is empty.

Specified by:

getFirst in interface Deque<E>

Returns:

the head element

Throws:

NoSuchElementException - if the deque is empty

See Also:

Deque.getFirst()

element

public E element()

Gets but does not remove the head element of this deque. It throws an exception if the deque is empty.

Specified by:

element in interface Queue<E>

Returns:

the head element

Throws:

NoSuchElementException - if the deque is empty

See Also:

Queue.element()

getLast

public E getLast()

Gets but not removes the tail element of this deque. This method throws an exception if the deque is empty.

Specified by:

getLast in interface Deque<E>

Returns:

the tail element

Throws:

NoSuchElementException - if the deque is empty

See Also:

Deque.getLast()

peekFirst

public E peekFirst()

Gets but not removes the head element of this deque. This method returns null if the deque is empty.

Specified by:

peekFirst in interface Deque<E>

Returns:

the head element or null if the deque is empty

See Also:

Deque.peekFirst()

peek

public E peek()

Gets but not removes the head element of this deque. This method returns null if the deque is empty.

Specified by:

peek in interface Queue<E>

Returns:

the head element or null if the deque is empty

See Also:

Queue.peek()

peekLast

public E peekLast()

Gets but not removes the tail element of this deque. This method returns null if the deque is empty.

Specified by:

peekLast in interface Deque<E>

Returns:

the tail element or null if the deque is empty

See Also:

Deque.peekLast()

removeFirstOccurrence

public boolean removeFirstOccurrence(Object obj)

Removes the first equivalent element of the specified object. If the deque does not contain the element, it is unchanged and returns false.

Specified by:

removeFirstOccurrence in interface Deque<E>

Parameters:

obj - the element to be removed

Returns:

true if the operation succeeds or false if the deque does not contain the element

See Also:

Deque.removeFirstOccurrence(java.lang.Object)

remove

public boolean remove(Object obj)

Removes the first equivalent element of the specified object. If the deque does not contain the element, it is unchanged and returns false.

Specified by:

remove in interface Collection<E>

Overrides:

remove in class AbstractCollection<E>

Parameters:

obj - the element to be removed

Returns:

true if the operation succeeds or false if the deque does not contain the element

See Also:

AbstractCollection.remove(java.lang.Object)

removeLastOccurrence

public boolean removeLastOccurrence(Object obj)

Removes the last equivalent element of the specified object. If the deque does not contain the element, it is unchanged and returns false.

Specified by:

removeLastOccurrence in interface Deque<E>

Parameters:

obj - the element to be removed

Returns:

true if the operation succeeds or false if the deque does not contain the element.

See Also:

Deque.removeLastOccurrence(java.lang.Object)

size

public int size()

Returns the size of the deque.

Specified by:

size in interface Collection<E>

Specified by:

size in class AbstractCollection<E>

Returns:

the size of the deque

See Also:

AbstractCollection.size()

isEmpty

public boolean isEmpty()

Returns true if the deque has no elements.

Specified by:

isEmpty in interface Collection<E>

Overrides:

isEmpty in class AbstractCollection<E>

Returns:

true if the deque has no elements, false otherwise

See Also:

AbstractCollection.isEmpty()

contains

public boolean contains(Object obj)

Returns true if the specified element is in the deque.

Specified by:

contains in interface Collection<E>

Overrides:

contains in class AbstractCollection<E>

Parameters:

obj - the element

Returns:

true if the element is in the deque, false otherwise

See Also:

AbstractCollection.contains(java.lang.Object)

clear

public void clear()

Empty the deque.

Specified by:

clear in interface Collection<E>

Overrides:

clear in class AbstractCollection<E>

See Also:

AbstractCollection.clear()

iterator

public Iterator<E> iterator()

Returns the iterator of the deque. The elements will be ordered from head to tail.

Specified by:

iterator in interface Iterable<E>

Specified by:

iterator in interface Collection<E>

Specified by:

iterator in class AbstractCollection<E>

Returns:

the iterator

See Also:

AbstractCollection.iterator()

descendingIterator

public Iterator<E> descendingIterator()

Returns the iterator in reverse order, from tail to head.

Specified by:

descendingIterator in interface Deque<E>

Returns:

the reverse order Iterator

See Also:

Deque.descendingIterator()