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
    Description
    ArrayDeque()
    Constructs a new empty instance of ArrayDeque big enough for 16 elements.
    ArrayDeque(int minSize)
    Constructs a new empty instance of ArrayDeque big enough for specified number of 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.

  • Method Summary

    Modifier and Type
    Method
    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 AbstractCollection

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

    Methods inherited from class Object

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

    Methods inherited from interface Collection

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

  • Constructor Details

    • 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 Details

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • 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:

    • clear

      public void clear()
      Empty the deque.
      Specified by:
      clear in interface Collection<E>
      Overrides:
      clear in class AbstractCollection<E>
      See Also:

    • 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 Collection<E>
      Specified by:
      iterator in interface Iterable<E>
      Specified by:
      iterator in class AbstractCollection<E>
      Returns:
      the iterator
      See Also:

    • 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: