Added in API level 21

ConcurrentLinkedDeque

open class ConcurrentLinkedDeque<E : Any!> : AbstractCollection<E>, Deque<E>, Serializable
kotlin.Any
   ↳ java.util.AbstractCollection<E>
   ↳ java.util.concurrent.ConcurrentLinkedDeque

An unbounded concurrent deque based on linked nodes. Concurrent insertion, removal, and access operations execute safely across multiple threads. A ConcurrentLinkedDeque is an appropriate choice when many threads will share access to a common collection. Like most other concurrent collection implementations, this class does not permit the use of null elements.

Iterators and spliterators are weakly consistent.

Beware that, unlike in most collections, the size method is NOT a constant-time operation. Because of the asynchronous nature of these deques, determining the current number of elements requires a traversal of the elements, and so may report inaccurate results if this collection is modified during traversal.

Bulk operations that add, remove, or examine multiple elements, such as #addAll, removeIf or forEach, are not guaranteed to be performed atomically. For example, a forEach traversal concurrent with an addAll operation might observe only some of the added elements.

This class and its iterator implement all of the optional methods of the Deque and Iterator interfaces.

Memory consistency effects: As with other concurrent collections, actions in a thread prior to placing an object into a ConcurrentLinkedDeque happen-before actions subsequent to the access or removal of that element from the ConcurrentLinkedDeque in another thread.

This class is a member of the Java Collections Framework.

Summary

Public constructors

Constructs an empty deque.

Constructs a deque initially containing the elements of the given collection, added in traversal order of the collection's iterator.

Public methods
open Boolean
add(element: E)

Inserts the specified element at the tail of this deque.

open Boolean
addAll(elements: Collection<E>)

Appends all of the elements in the specified collection to the end of this deque, in the order that they are returned by the specified collection's iterator.

open Unit
addFirst(e: E)

Inserts the specified element at the front of this deque.

open Unit
addLast(e: E)

Inserts the specified element at the end of this deque.

open Unit

Removes all of the elements from this deque.

open Boolean
contains(element: E?)

Returns true if this deque contains the specified element.

open MutableIterator<E>

Returns an iterator over the elements in this deque in reverse sequential order.

open E

open Unit
forEach(action: Consumer<in E>)

open E

open E

open Boolean

Returns true if this collection contains no elements.

open MutableIterator<E>

Returns an iterator over the elements in this deque in proper sequence.

open Boolean
offer(e: E)

Inserts the specified element at the tail of this deque.

open Boolean
offerFirst(e: E)

Inserts the specified element at the front of this deque.

open Boolean
offerLast(e: E)

Inserts the specified element at the end of this deque.

open E?

open E?

open E?

open E?

open E?

open E?

open E
pop()

open Unit
push(e: E)

open E

open Boolean
remove(element: E?)

Removes the first occurrence of the specified element from this deque.

open Boolean
removeAll(elements: Collection<E>)

open E

open Boolean

Removes the first occurrence of the specified element from this deque.

open Boolean
removeIf(filter: Predicate<in E>)

open E

open Boolean

Removes the last occurrence of the specified element from this deque.

open Boolean
retainAll(elements: Collection<E>)

open Spliterator<E>

Returns a Spliterator over the elements in this deque.

open Array<Any!>

Returns an array containing all of the elements in this deque, in proper sequence (from first to last element).

open Array<T>
toArray(a: 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.

open String

Inherited functions
Properties
open Int

Returns the number of elements in this deque.

Public constructors

ConcurrentLinkedDeque

Added in API level 21
ConcurrentLinkedDeque()

Constructs an empty deque.

ConcurrentLinkedDeque

Added in API level 21
ConcurrentLinkedDeque(c: MutableCollection<out E>!)

Constructs a deque initially containing the elements of the given collection, added in traversal order of the collection's iterator.

Parameters
c MutableCollection<out E>!: the collection of elements to initially contain
Exceptions
java.lang.NullPointerException if the specified collection or any of its elements are null

Public methods

add

Added in API level 21
open fun add(element: E): Boolean

Inserts the specified element at the tail of this deque. As the deque is unbounded, this method will never throw IllegalStateException or return false.

Parameters
e the element to add
Return
Boolean true (as specified by Collection#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

Added in API level 21
open fun addAll(elements: Collection<E>): Boolean

Appends all of the elements in the specified collection to the end of this deque, in the order that they are returned by the specified collection's iterator. Attempts to addAll of a deque to itself result in IllegalArgumentException.

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 the collection is this deque
java.lang.IllegalStateException if not all the elements can be added at this time due to insertion restrictions

addFirst

Added in API level 21
open fun addFirst(e: E): Unit

Inserts the specified element at the front of this deque. As the deque is unbounded, this method will never throw IllegalStateException.

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

Added in API level 21
open fun addLast(e: E): Unit

Inserts the specified element at the end of this deque. As the deque is unbounded, this method will never throw IllegalStateException.

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

Added in API level 21
open fun clear(): Unit

Removes all of the elements from this deque.

Exceptions
java.lang.UnsupportedOperationException if the clear operation is not supported by this collection

contains

Added in API level 21
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 element whose presence in this deque is to be tested
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

Added in API level 21
open fun descendingIterator(): MutableIterator<E>

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).

The returned iterator is weakly consistent.

Return
MutableIterator<E> an iterator over the elements in this deque in reverse order

element

Added in API level 21
open fun element(): E
Return
E the head of the queue represented by this deque
Exceptions
java.util.NoSuchElementException if this deque is empty

forEach

Added in API level 24
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

Added in API level 21
open fun getFirst(): E
Return
E the head of this deque
Exceptions
java.util.NoSuchElementException if this deque is empty

getLast

Added in API level 21
open fun getLast(): E
Return
E the tail of this deque
Exceptions
java.util.NoSuchElementException if this deque is empty

isEmpty

Added in API level 21
open fun isEmpty(): Boolean

Returns true if this collection contains no elements.

Return
Boolean true if this collection contains no elements

iterator

Added in API level 21
open fun iterator(): MutableIterator<E>

Returns an iterator over the elements in this deque in proper sequence. The elements will be returned in order from first (head) to last (tail).

The returned iterator is weakly consistent.

Return
MutableIterator<E> an iterator over the elements in this deque in proper sequence

offer

Added in API level 21
open fun offer(e: E): Boolean

Inserts the specified element at the tail of this deque. As the deque is unbounded, this method will never return false.

Parameters
e E: the element to add
Return
Boolean true (as specified by Queue#offer)
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

Added in API level 21
open fun offerFirst(e: E): Boolean

Inserts the specified element at the front of this deque. As the deque is unbounded, this method will never return false.

Parameters
e E: the element to add
Return
Boolean true (as specified by Deque#offerFirst)
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

Added in API level 21
open fun offerLast(e: E): Boolean

Inserts the specified element at the end of this deque. As the deque is unbounded, this method will never return false.

This method is equivalent to #add.

Parameters
e E: the element to add
Return
Boolean true (as specified by Deque#offerLast)
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

Added in API level 21
open fun peek(): E?
Return
E? the head of the queue represented by this deque, or null if this deque is empty

peekFirst

Added in API level 21
open fun peekFirst(): E?
Return
E? the head of this deque, or null if this deque is empty

peekLast

Added in API level 21
open fun peekLast(): E?
Return
E? the tail of this deque, or null if this deque is empty

poll

Added in API level 21
open fun poll(): E?
Return
E? the first element of this deque, or null if this deque is empty

pollFirst

Added in API level 21
open fun pollFirst(): E?
Return
E? the head of this deque, or null if this deque is empty

pollLast

Added in API level 21
open fun pollLast(): E?
Return
E? the tail of this deque, or null if this deque is empty

pop

Added in API level 21
open fun pop(): E
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

Added in API level 21
open fun push(e: E): Unit
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 and this deque does not permit null elements
java.lang.IllegalArgumentException if some property of the specified element prevents it from being added to this deque

remove

Added in API level 21
open fun remove(): E
Return
E the head of the queue represented by this deque
Exceptions
java.util.NoSuchElementException if this deque is empty

remove

Added in API level 21
open fun remove(element: E?): Boolean

Removes the first occurrence 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 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
java.lang.UnsupportedOperationException if the remove operation is not supported by this collection

removeAll

Added in API level 21
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 (optional)
java.lang.NullPointerException if this collection contains one or more null elements and the specified collection does not support null elements (optional), or if the specified collection is null

removeFirst

Added in API level 21
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

Added in API level 21
open fun removeFirstOccurrence(o: Any?): Boolean

Removes the first occurrence 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).

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

removeIf

Added in API level 24
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

Added in API level 21
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

Added in API level 21
open fun removeLastOccurrence(o: Any?): Boolean

Removes the last occurrence of the specified element from this deque. 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

retainAll

Added in API level 21
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 (optional)
java.lang.NullPointerException if this collection contains one or more null elements and the specified collection does not permit null elements (optional), or if the specified collection is null

spliterator

Added in API level 24
open fun spliterator(): Spliterator<E>

Returns a Spliterator over the elements in this deque.

The returned spliterator is weakly consistent.

The Spliterator reports Spliterator#CONCURRENT, Spliterator#ORDERED, and Spliterator#NONNULL.

Return
Spliterator<E> a Spliterator over the elements in this deque

toArray

Added in API level 21
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

Added in API level 21
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

toString

Added in API level 21
open fun toString(): String
Return
String a string representation of the object.

Properties

size

Added in API level 21
open val size: Int

Returns the number of elements in this deque. If this deque contains more than Integer.MAX_VALUE elements, it returns Integer.MAX_VALUE.

Beware that, unlike in most collections, this method is NOT a constant-time operation. Because of the asynchronous nature of these deques, determining the current number of elements requires traversing them all to count them. Additionally, it is possible for the size to change during execution of this method, in which case the returned result will be inaccurate. Thus, this method is typically not very useful in concurrent applications.

Return
Int the number of elements in this deque