ArrayDeque

public class ArrayDeque 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.

Public Constructor Summary

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.

Public Method Summary

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.

Inherited Method Summary