ArrayDeque
open class ArrayDeque<E : Any!> : AbstractCollection<E>, Cloneable, Deque<E>, 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(java.lang.Object), removeFirstOccurrence, removeLastOccurrence, #contains, #iterator, 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, SequencedCollection, and Iterator interfaces.
This class is a member of the Java Collections Framework.
Summary
| Public constructors |
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Constructs an empty array deque with an initial capacity sufficient to hold 16 elements.
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Constructs an empty array deque with an initial capacity sufficient to hold the specified number of elements.
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Constructs a deque containing the elements of the specified collection, in the order they are returned by the collection's iterator.
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| Public methods |
| open Boolean |
Inserts the specified element at the end of this deque.
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| open Boolean |
Adds all of the elements in the specified collection at the end of this deque, as if by calling #addLast on each one, in the order that they are returned by the collection's iterator.
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| open Unit |
Inserts the specified element at the front of this deque.
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| open Unit |
Inserts the specified element at the end of this deque.
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| open Unit |
Removes all of the elements from this deque.
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| open ArrayDeque<E> |
Returns a copy of this deque.
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| open Boolean |
Returns true if this deque contains the specified element.
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| open MutableIterator<E> |
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| open E |
Retrieves, but does not remove, the head of the queue represented by this deque.
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| open Unit |
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| open E |
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| open E |
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| open Boolean |
Returns true if this deque contains no elements.
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| open MutableIterator<E> |
Returns an iterator over the elements in this deque.
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| open Boolean |
Inserts the specified element at the end of this deque.
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| open Boolean |
Inserts the specified element at the front of this deque.
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| open Boolean |
Inserts the specified element at the end of this deque.
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| open E? |
Retrieves, but does not remove, the head of the queue represented by this deque, or returns null if this deque is empty.
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| open E? |
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| open E? |
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| open E? |
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.
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| open E? |
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| open E? |
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| open E |
Pops an element from the stack represented by this deque.
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| open Unit |
Pushes an element onto the stack represented by this deque.
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| open E |
Retrieves and removes the head of the queue represented by this deque.
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| open Boolean |
Removes a single instance of the specified element from this deque.
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| open Boolean |
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| open E |
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| open Boolean |
Removes the first occurrence of the specified element in this deque (when traversing the deque from head to tail).
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| open Boolean |
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| open E |
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| open Boolean |
Removes the last occurrence of the specified element in this deque (when traversing the deque from head to tail).
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| open Boolean |
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| open Spliterator<E> |
Creates a late-binding and fail-fast Spliterator over the elements in this deque.
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| open Array<Any!> |
Returns an array containing all of the elements in this deque in proper sequence (from first to last element).
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| open Array<T> |
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.
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| Inherited functions |
From class AbstractCollection
Boolean |
containsAll(elements: Collection<E>)
Returns true if this collection contains all of the elements in the specified collection.
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String |
toString()
Returns a string representation of this collection. The string representation consists of a list of the collection's elements in the order they are returned by its iterator, enclosed in square brackets ("[]"). Adjacent elements are separated by the characters ", " (comma and space). Elements are converted to strings as by String.valueOf(Object).
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From class Deque
Deque<E> |
reversed()
Returns a reverse-ordered view of this collection. The encounter order of elements in the returned view is the inverse of the encounter order of elements in this collection. The reverse ordering affects all order-sensitive operations, including those on the view collections of the returned view. If the collection implementation permits modifications to this view, the modifications "write through" to the underlying collection. Changes to the underlying collection might or might not be visible in this reversed view, depending upon the implementation.
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| Properties |
| open Int |
Returns the number of elements in this deque.
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Public constructors
ArrayDeque
ArrayDeque()
Constructs an empty array deque with an initial capacity sufficient to hold 16 elements.
ArrayDeque
ArrayDeque(numElements: Int)
Constructs an empty array deque with an initial capacity sufficient to hold the specified number of elements.
| Parameters |
numElements |
Int: lower bound on initial capacity of the deque |
ArrayDeque
ArrayDeque(c: MutableCollection<out E>)
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 |
MutableCollection<out E>: the collection whose elements are to be placed into the deque |
| Exceptions |
java.lang.NullPointerException |
if the specified collection is null |
Public methods
add
open fun add(element: E): Boolean
Inserts the specified element at the end of this deque.
This method is equivalent to #addLast.
| Parameters |
e |
the element to add |
| Exceptions |
java.lang.UnsupportedOperationException |
if the add operation is not supported by this collection |
java.lang.ClassCastException |
if the class of the specified element prevents it from being added to this deque |
java.lang.NullPointerException |
if the specified element is null |
java.lang.IllegalArgumentException |
if some property of the specified element prevents it from being added to this deque |
java.lang.IllegalStateException |
if the element cannot be added at this time due to capacity restrictions |
addAll
open fun addAll(elements: Collection<E>): Boolean
Adds all of the elements in the specified collection at the end of this deque, as if by calling #addLast on each one, in the order that they are returned by the collection's iterator.
| Parameters |
c |
the elements to be inserted into this deque |
| Return |
Boolean |
true if this deque changed as a result of the call |
| Exceptions |
java.lang.UnsupportedOperationException |
if the addAll operation is not supported by this collection |
java.lang.ClassCastException |
if the class of an element of the specified collection prevents it from being added to this deque |
java.lang.NullPointerException |
if the specified collection or any of its elements are null |
java.lang.IllegalArgumentException |
if some property of an element of the specified collection prevents it from being added to this deque |
java.lang.IllegalStateException |
if not all the elements can be added at this time due to insertion restrictions |
addFirst
open fun addFirst(e: E): Unit
Inserts the specified element at the front of this deque.
| Parameters |
e |
E: the element to add |
| Exceptions |
java.lang.NullPointerException |
if the specified element is null |
java.lang.UnsupportedOperationException |
if this collection implementation does not support this operation |
java.lang.IllegalStateException |
if the element cannot be added at this time due to capacity restrictions |
java.lang.ClassCastException |
if the class of the specified element prevents it from being added to this deque |
java.lang.IllegalArgumentException |
if some property of the specified element prevents it from being added to this deque |
addLast
open fun addLast(e: E): Unit
Inserts the specified element at the end of this deque.
This method is equivalent to #add.
| Parameters |
e |
E: the element to add |
| Exceptions |
java.lang.NullPointerException |
if the specified element is null |
java.lang.UnsupportedOperationException |
if this collection implementation does not support this operation |
java.lang.IllegalStateException |
if the element cannot be added at this time due to capacity restrictions |
java.lang.ClassCastException |
if the class of the specified element prevents it from being added to this deque |
java.lang.IllegalArgumentException |
if some property of the specified element prevents it from being added to this deque |
clear
open fun clear(): Unit
Removes all of the elements from this deque. The deque will be empty after this call returns.
| Exceptions |
java.lang.UnsupportedOperationException |
if the clear operation is not supported by this collection |
clone
open fun clone(): ArrayDeque<E>
Returns a copy of this deque.
| Exceptions |
java.lang.CloneNotSupportedException |
if the object's class does not support the Cloneable interface. Subclasses that override the clone method can also throw this exception to indicate that an instance cannot be cloned. |
contains
open fun contains(element: E?): Boolean
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).
| Parameters |
o |
object to be checked for containment in this deque |
| Return |
Boolean |
true if this deque contains the specified element |
| Exceptions |
java.lang.ClassCastException |
if the class of the specified element is incompatible with this deque (java.util.Collection#) |
java.lang.NullPointerException |
if the specified element is null and this deque does not permit null elements (java.util.Collection#) |
descendingIterator
open fun descendingIterator(): MutableIterator<E>
| Return |
MutableIterator<E> |
an iterator over the elements in this deque in reverse sequence |
element
open fun element(): E
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.
| Return |
E |
the head of the queue represented by this deque |
| Exceptions |
java.util.NoSuchElementException |
if this deque is empty |
forEach
open fun forEach(action: Consumer<in E>): Unit
| Parameters |
action |
Consumer<in E>: The action to be performed for each element |
| Exceptions |
java.lang.NullPointerException |
if the specified action is null |
getFirst
open fun getFirst(): E
| Return |
E |
the head of this deque |
| Exceptions |
java.util.NoSuchElementException |
if this deque is empty |
getLast
open fun getLast(): E
| Return |
E |
the tail of this deque |
| Exceptions |
java.util.NoSuchElementException |
if this deque is empty |
isEmpty
open fun isEmpty(): Boolean
Returns true if this deque contains no elements.
| Return |
Boolean |
true if this deque contains no elements |
iterator
open fun iterator(): MutableIterator<E>
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).
offer
open fun offer(e: E): Boolean
Inserts the specified element at the end of this deque.
This method is equivalent to offerLast.
| Parameters |
e |
E: the element to add |
| Exceptions |
java.lang.ClassCastException |
if the class of the specified element prevents it from being added to this deque |
java.lang.NullPointerException |
if the specified element is null |
java.lang.IllegalArgumentException |
if some property of the specified element prevents it from being added to this deque |
offerFirst
open fun offerFirst(e: E): Boolean
Inserts the specified element at the front of this deque.
| Parameters |
e |
E: the element to add |
| Exceptions |
java.lang.ClassCastException |
if the class of the specified element prevents it from being added to this deque |
java.lang.NullPointerException |
if the specified element is null |
java.lang.IllegalArgumentException |
if some property of the specified element prevents it from being added to this deque |
offerLast
open fun offerLast(e: E): Boolean
Inserts the specified element at the end of this deque.
| Parameters |
e |
E: the element to add |
| Exceptions |
java.lang.ClassCastException |
if the class of the specified element prevents it from being added to this deque |
java.lang.NullPointerException |
if the specified element is null |
java.lang.IllegalArgumentException |
if some property of the specified element prevents it from being added to this deque |
peek
open fun peek(): E?
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.
| Return |
E? |
the head of the queue represented by this deque, or null if this deque is empty |
peekFirst
open fun peekFirst(): E?
| Return |
E? |
the head of this deque, or null if this deque is empty |
peekLast
open fun peekLast(): E?
| Return |
E? |
the tail of this deque, or null if this deque is empty |
poll
open fun poll(): E?
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.
| Return |
E? |
the head of the queue represented by this deque, or null if this deque is empty |
pollFirst
open fun pollFirst(): E?
| Return |
E? |
the head of this deque, or null if this deque is empty |
pollLast
open fun pollLast(): E?
| Return |
E? |
the tail of this deque, or null if this deque is empty |
pop
open fun pop(): E
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().
| Return |
E |
the element at the front of this deque (which is the top of the stack represented by this deque) |
| Exceptions |
java.util.NoSuchElementException |
if this deque is empty |
push
open fun push(e: E): Unit
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.
| Parameters |
e |
E: the element to push |
| Exceptions |
java.lang.IllegalStateException |
if the element cannot be added at this time due to capacity restrictions |
java.lang.ClassCastException |
if the class of the specified element prevents it from being added to this deque |
java.lang.NullPointerException |
if the specified element is null |
java.lang.IllegalArgumentException |
if some property of the specified element prevents it from being added to this deque |
remove
open fun remove(): E
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.
| Return |
E |
the head of the queue represented by this deque |
| Exceptions |
java.util.NoSuchElementException |
if this deque is empty |
remove
open fun remove(element: E?): Boolean
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).
| Parameters |
o |
element to be removed from this deque, if present |
| Return |
Boolean |
true if this deque contained the specified element |
| Exceptions |
java.lang.ClassCastException |
if the class of the specified element is incompatible with this deque (java.util.Collection#) |
java.lang.NullPointerException |
if the specified element is null and this deque does not permit null elements (java.util.Collection#) |
java.lang.UnsupportedOperationException |
if the remove operation is not supported by this collection |
removeAll
open fun removeAll(elements: Collection<E>): Boolean
| Parameters |
c |
collection containing elements to be removed from this collection |
| Return |
Boolean |
true if this collection changed as a result of the call |
| Exceptions |
java.lang.UnsupportedOperationException |
if the removeAll method is not supported by this collection |
java.lang.ClassCastException |
if the types of one or more elements in this collection are incompatible with the specified collection (java.util.Collection#) |
java.lang.NullPointerException |
if this collection contains one or more null elements and the specified collection does not support null elements (java.util.Collection#) or if the specified collection is null |
removeFirst
open fun removeFirst(): E
| Return |
E |
the head of this deque |
| Exceptions |
java.util.NoSuchElementException |
if this deque is empty |
java.lang.UnsupportedOperationException |
if this collection implementation does not support this operation |
removeFirstOccurrence
open fun removeFirstOccurrence(o: Any?): Boolean
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).
| Parameters |
o |
Any?: element to be removed from this deque, if present |
| Return |
Boolean |
true if the deque contained the specified element |
| Exceptions |
java.lang.ClassCastException |
if the class of the specified element is incompatible with this deque (java.util.Collection#) |
java.lang.NullPointerException |
if the specified element is null and this deque does not permit null elements (java.util.Collection#) |
removeIf
open fun removeIf(filter: Predicate<in E>): Boolean
| Parameters |
filter |
Predicate<in E>: a predicate which returns true for elements to be removed |
| Return |
Boolean |
true if any elements were removed |
| Exceptions |
java.lang.NullPointerException |
if the specified filter is null |
java.lang.UnsupportedOperationException |
if elements cannot be removed from this collection. Implementations may throw this exception if a matching element cannot be removed or if, in general, removal is not supported. |
removeLast
open fun removeLast(): E
| Return |
E |
the tail of this deque |
| Exceptions |
java.util.NoSuchElementException |
if this deque is empty |
java.lang.UnsupportedOperationException |
if this collection implementation does not support this operation |
removeLastOccurrence
open fun removeLastOccurrence(o: Any?): Boolean
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).
| Parameters |
o |
Any?: element to be removed from this deque, if present |
| Return |
Boolean |
true if the deque contained the specified element |
| Exceptions |
java.lang.ClassCastException |
if the class of the specified element is incompatible with this deque (java.util.Collection#) |
java.lang.NullPointerException |
if the specified element is null and this deque does not permit null elements (java.util.Collection#) |
retainAll
open fun retainAll(elements: Collection<E>): Boolean
| Parameters |
c |
collection containing elements to be retained in this collection |
| Return |
Boolean |
true if this collection changed as a result of the call |
| Exceptions |
java.lang.UnsupportedOperationException |
if the retainAll operation is not supported by this collection |
java.lang.ClassCastException |
if the types of one or more elements in this collection are incompatible with the specified collection (java.util.Collection#) |
java.lang.NullPointerException |
if this collection contains one or more null elements and the specified collection does not permit null elements (java.util.Collection#) or if the specified collection is null |
toArray
open fun toArray(): Array<Any!>
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.
| Return |
Array<Any!> |
an array containing all of the elements in this deque |
toArray
open fun <T : Any!> toArray(a: Array<T>): Array<T>
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:
<code>String[] y = x.toArray(new String[0]);</code>
Note that
toArray(new Object[0]) is identical in function to
toArray().
| Parameters |
<T> |
the component type of the array to contain the collection |
a |
Array<T>: 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 |
| Return |
Array<T> |
an array containing all of the elements in this deque |
| Exceptions |
java.lang.ArrayStoreException |
if the runtime type of the specified array is not a supertype of the runtime type of every element in this deque |
java.lang.NullPointerException |
if the specified array is null |
Properties
size
open val size: Int
Returns the number of elements in this deque.
| Return |
Int |
the number of elements in this deque |
