ArrayDeque (Java Platform SE 6) (original) (raw)
java.util
Class ArrayDeque
java.lang.Object
java.util.AbstractCollection
java.util.ArrayDeque
Type Parameters:
E - the type of elements held in this collection
All Implemented Interfaces:
Serializable, Cloneable, Iterable, Collection, Deque, Queue
public class ArrayDeque
extends AbstractCollection
implements Deque, 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 thanStack 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.
Since:
1.6
See Also:
| Constructor Summary |
|---|
| ArrayDeque() Constructs an empty array deque with an initial capacity sufficient to hold 16 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. |
| ArrayDeque(int numElements) Constructs an empty array deque with an initial capacity sufficient to hold the specified number of elements. |
| 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 returnsnull 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. |
| Object[] | toArray() Returns an array containing all of the elements in this deque in proper sequence (from first to last element). |
| 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. |
| Methods inherited from class java.util.AbstractCollection |
|---|
| addAll, containsAll, removeAll, retainAll, toString |
| Methods inherited from class java.lang.Object |
|---|
| equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, [wait](../../java/lang/Object.html#wait%28long, int%29) |
| Methods inherited from interface java.util.Collection |
|---|
| addAll, containsAll, equals, hashCode, removeAll, retainAll |
| Constructor Detail |
|---|
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.
Parameters:
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.)
Parameters:
c - the collection whose elements are to be placed into the deque
Throws:
[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang") - if the specified collection is null
| Method Detail |
|---|
addFirst
public void addFirst(E e)
Inserts the specified element at the front of this deque.
Specified by:
[addFirst](../../java/util/Deque.html#addFirst%28E%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Parameters:
e - the element to add
Throws:
[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang") - 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).
Specified by:
[addLast](../../java/util/Deque.html#addLast%28E%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Parameters:
e - the element to add
Throws:
[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang") - if the specified element is null
offerFirst
public boolean offerFirst(E e)
Inserts the specified element at the front of this deque.
Specified by:
[offerFirst](../../java/util/Deque.html#offerFirst%28E%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Parameters:
e - the element to add
Returns:
true (as specified by Deque.offerFirst(E))
Throws:
[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang") - if the specified element is null
offerLast
public boolean offerLast(E e)
Inserts the specified element at the end of this deque.
Specified by:
[offerLast](../../java/util/Deque.html#offerLast%28E%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Parameters:
e - the element to add
Returns:
true (as specified by Deque.offerLast(E))
Throws:
[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang") - if the specified element is null
removeFirst
public E removeFirst()
Description copied from interface: [Deque](../../java/util/Deque.html#removeFirst%28%29)
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.
Specified by:
[removeFirst](../../java/util/Deque.html#removeFirst%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
the head of this deque
Throws:
[NoSuchElementException](../../java/util/NoSuchElementException.html "class in java.util") - if this deque is empty
removeLast
public E removeLast()
Description copied from interface: [Deque](../../java/util/Deque.html#removeLast%28%29)
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.
Specified by:
[removeLast](../../java/util/Deque.html#removeLast%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
the tail of this deque
Throws:
[NoSuchElementException](../../java/util/NoSuchElementException.html "class in java.util") - if this deque is empty
pollFirst
public E pollFirst()
Description copied from interface: [Deque](../../java/util/Deque.html#pollFirst%28%29)
Retrieves and removes the first element of this deque, or returns null if this deque is empty.
Specified by:
[pollFirst](../../java/util/Deque.html#pollFirst%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
the head of this deque, or null if this deque is empty
pollLast
public E pollLast()
Description copied from interface: [Deque](../../java/util/Deque.html#pollLast%28%29)
Retrieves and removes the last element of this deque, or returns null if this deque is empty.
Specified by:
[pollLast](../../java/util/Deque.html#pollLast%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
the tail of this deque, or null if this deque is empty
getFirst
public E getFirst()
Description copied from interface: [Deque](../../java/util/Deque.html#getFirst%28%29)
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.
Specified by:
[getFirst](../../java/util/Deque.html#getFirst%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
the head of this deque
Throws:
[NoSuchElementException](../../java/util/NoSuchElementException.html "class in java.util") - if this deque is empty
getLast
public E getLast()
Description copied from interface: [Deque](../../java/util/Deque.html#getLast%28%29)
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.
Specified by:
[getLast](../../java/util/Deque.html#getLast%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
the tail of this deque
Throws:
[NoSuchElementException](../../java/util/NoSuchElementException.html "class in java.util") - if this deque is empty
peekFirst
public E peekFirst()
Description copied from interface: [Deque](../../java/util/Deque.html#peekFirst%28%29)
Retrieves, but does not remove, the first element of this deque, or returns null if this deque is empty.
Specified by:
[peekFirst](../../java/util/Deque.html#peekFirst%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
the head of this deque, or null if this deque is empty
peekLast
public E peekLast()
Description copied from interface: [Deque](../../java/util/Deque.html#peekLast%28%29)
Retrieves, but does not remove, the last element of this deque, or returns null if this deque is empty.
Specified by:
[peekLast](../../java/util/Deque.html#peekLast%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
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 thato.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).
Specified by:
[removeFirstOccurrence](../../java/util/Deque.html#removeFirstOccurrence%28java.lang.Object%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Parameters:
o - element to be removed from this deque, if present
Returns:
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 thato.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).
Specified by:
[removeLastOccurrence](../../java/util/Deque.html#removeLastOccurrence%28java.lang.Object%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Parameters:
o - element to be removed from this deque, if present
Returns:
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).
Specified by:
[add](../../java/util/Collection.html#add%28E%29) in interface [Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Specified by:
[add](../../java/util/Deque.html#add%28E%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Specified by:
[add](../../java/util/Queue.html#add%28E%29) in interface [Queue](../../java/util/Queue.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Overrides:
[add](../../java/util/AbstractCollection.html#add%28E%29) in class [AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Parameters:
e - the element to add
Returns:
true (as specified by Collection.add(E))
Throws:
[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang") - 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).
Specified by:
[offer](../../java/util/Deque.html#offer%28E%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Specified by:
[offer](../../java/util/Queue.html#offer%28E%29) in interface [Queue](../../java/util/Queue.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Parameters:
e - the element to add
Returns:
true (as specified by Queue.offer(E))
Throws:
[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang") - 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().
Specified by:
[remove](../../java/util/Deque.html#remove%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Specified by:
[remove](../../java/util/Queue.html#remove%28%29) in interface [Queue](../../java/util/Queue.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
the head of the queue represented by this deque
Throws:
[NoSuchElementException](../../java/util/NoSuchElementException.html "class in java.util") - 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 returnsnull if this deque is empty.
This method is equivalent to pollFirst().
Specified by:
[poll](../../java/util/Deque.html#poll%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Specified by:
[poll](../../java/util/Queue.html#poll%28%29) in interface [Queue](../../java/util/Queue.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
the head of the queue represented by this deque, ornull 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().
Specified by:
[element](../../java/util/Deque.html#element%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Specified by:
[element](../../java/util/Queue.html#element%28%29) in interface [Queue](../../java/util/Queue.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
the head of the queue represented by this deque
Throws:
[NoSuchElementException](../../java/util/NoSuchElementException.html "class in java.util") - 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().
Specified by:
[peek](../../java/util/Deque.html#peek%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Specified by:
[peek](../../java/util/Queue.html#peek%28%29) in interface [Queue](../../java/util/Queue.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
the head of the queue represented by this deque, ornull 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).
Specified by:
[push](../../java/util/Deque.html#push%28E%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Parameters:
e - the element to push
Throws:
[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang") - 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().
Specified by:
[pop](../../java/util/Deque.html#pop%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
the element at the front of this deque (which is the top of the stack represented by this deque)
Throws:
[NoSuchElementException](../../java/util/NoSuchElementException.html "class in java.util") - if this deque is empty
size
public int size()
Returns the number of elements in this deque.
Specified by:
[size](../../java/util/Collection.html#size%28%29) in interface [Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Specified by:
[size](../../java/util/Deque.html#size%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Specified by:
[size](../../java/util/AbstractCollection.html#size%28%29) in class [AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
the number of elements in this deque
isEmpty
public boolean isEmpty()
Returns true if this deque contains no elements.
Specified by:
[isEmpty](../../java/util/Collection.html#isEmpty%28%29) in interface [Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Overrides:
[isEmpty](../../java/util/AbstractCollection.html#isEmpty%28%29) in class [AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
true if this deque contains no elements
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 toremove() or popped (via successive calls to pop()).
Specified by:
[iterator](../../java/lang/Iterable.html#iterator%28%29) in interface [Iterable](../../java/lang/Iterable.html "interface in java.lang")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Specified by:
[iterator](../../java/util/Collection.html#iterator%28%29) in interface [Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Specified by:
[iterator](../../java/util/Deque.html#iterator%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Specified by:
[iterator](../../java/util/AbstractCollection.html#iterator%28%29) in class [AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
an iterator over the elements in this deque
descendingIterator
public Iterator<E> descendingIterator()
Description copied from interface: [Deque](../../java/util/Deque.html#descendingIterator%28%29)
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).
Specified by:
[descendingIterator](../../java/util/Deque.html#descendingIterator%28%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
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).
Specified by:
[contains](../../java/util/Collection.html#contains%28java.lang.Object%29) in interface [Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Specified by:
[contains](../../java/util/Deque.html#contains%28java.lang.Object%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Overrides:
[contains](../../java/util/AbstractCollection.html#contains%28java.lang.Object%29) in class [AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Parameters:
o - object to be checked for containment in this deque
Returns:
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 thato.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).
Specified by:
[remove](../../java/util/Collection.html#remove%28java.lang.Object%29) in interface [Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Specified by:
[remove](../../java/util/Deque.html#remove%28java.lang.Object%29) in interface [Deque](../../java/util/Deque.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Overrides:
[remove](../../java/util/AbstractCollection.html#remove%28java.lang.Object%29) in class [AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Parameters:
o - element to be removed from this deque, if present
Returns:
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.
Specified by:
[clear](../../java/util/Collection.html#clear%28%29) in interface [Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Overrides:
[clear](../../java/util/AbstractCollection.html#clear%28%29) in class [AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
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.
Specified by:
[toArray](../../java/util/Collection.html#toArray%28%29) in interface [Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Overrides:
[toArray](../../java/util/AbstractCollection.html#toArray%28%29) in class [AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Returns:
an array containing all of the elements in this deque
toArray
public 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 tonull.
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 totoArray().
Specified by:
[toArray](../../java/util/Collection.html#toArray%28T[]%29) in interface [Collection](../../java/util/Collection.html "interface in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Overrides:
[toArray](../../java/util/AbstractCollection.html#toArray%28T[]%29) in class [AbstractCollection](../../java/util/AbstractCollection.html "class in java.util")<[E](../../java/util/ArrayDeque.html "type parameter in ArrayDeque")>
Parameters:
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
Returns:
an array containing all of the elements in this deque
Throws:
[ArrayStoreException](../../java/lang/ArrayStoreException.html "class in java.lang") - if the runtime type of the specified array is not a supertype of the runtime type of every element in this deque
[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang") - if the specified array is null
clone
public ArrayDeque<E> clone()
Returns a copy of this deque.
Overrides:
[clone](../../java/lang/Object.html#clone%28%29) in class [Object](../../java/lang/Object.html "class in java.lang")
Returns:
a copy of this deque
See Also:
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For further API reference and developer documentation, see Java SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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