Added in API level 9

LinkedBlockingDeque

open class LinkedBlockingDeque<E : Any!> : AbstractQueue<E>, BlockingDeque<E>, Serializable

kotlin.Any
↳	java.util.AbstractCollection<E>
	↳	java.util.AbstractQueue<E>
		↳	java.util.concurrent.LinkedBlockingDeque

An optionally-bounded blocking deque based on linked nodes.

The optional capacity bound constructor argument serves as a way to prevent excessive expansion. The capacity, if unspecified, is equal to Integer.MAX_VALUE. Linked nodes are dynamically created upon each insertion unless this would bring the deque above capacity.

Most operations run in constant time (ignoring time spent blocking). Exceptions include #remove(java.lang.Object), #removeFirstOccurrence, #removeLastOccurrence, #contains, #iterator, and the bulk operations, all of which run in linear time.

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.

Summary

Public constructors
`LinkedBlockingDeque()` Creates a `LinkedBlockingDeque` with a capacity of `Integer.MAX_VALUE`.
`LinkedBlockingDeque(capacity: Int)` Creates a `LinkedBlockingDeque` with the given (fixed) capacity.
`LinkedBlockingDeque(c: MutableCollection<out E>!)` Creates a `LinkedBlockingDeque` with a capacity of `Integer.MAX_VALUE`, 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 end of this deque unless it would violate capacity restrictions.
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)`
open Unit	`addLast(e: E)`
open Unit	`clear()` Atomically 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>	`descendingIterator()` Returns an iterator over the elements in this deque in reverse sequential order.
open Int	`drainTo(c: MutableCollection<in E>!)`
open Int	`drainTo(c: MutableCollection<in E>!, maxElements: Int)`
open E	`element()` Retrieves, but does not remove, the head of the queue represented by this deque.
open Unit	`forEach(action: Consumer<in E>)`
open E	`getFirst()`
open E	`getLast()`
open MutableIterator<E>	`iterator()` Returns an iterator over the elements in this deque in proper sequence.
open Boolean	`offer(e: E)`
open Boolean	`offer(e: E, timeout: Long, unit: TimeUnit!)`
open Boolean	`offerFirst(e: E)`
open Boolean	`offerFirst(e: E, timeout: Long, unit: TimeUnit!)`
open Boolean	`offerLast(e: E)`
open Boolean	`offerLast(e: E, timeout: Long, unit: TimeUnit!)`
open E?	`peek()`
open E?	`peekFirst()`
open E?	`peekLast()`
open E?	`poll()`
open E	`poll(timeout: Long, unit: TimeUnit!)`
open E?	`pollFirst()`
open E	`pollFirst(timeout: Long, unit: TimeUnit!)`
open E?	`pollLast()`
open E	`pollLast(timeout: Long, unit: TimeUnit!)`
open E	`pop()`
open Unit	`push(e: E)`
open Unit	`put(e: E)`
open Unit	`putFirst(e: E)`
open Unit	`putLast(e: E)`
open Int	`remainingCapacity()` Returns the number of additional elements that this deque can ideally (in the absence of memory or resource constraints) accept without blocking.
open E	`remove()` Retrieves and removes the head of the queue represented by this deque.
open Boolean	`remove(element: E?)` Removes the first occurrence of the specified element from this deque.
open Boolean	`removeAll(elements: Collection<E>)`
open E	`removeFirst()`
open Boolean	`removeFirstOccurrence(o: Any?)`
open Boolean	`removeIf(filter: Predicate<in E>)`
open E	`removeLast()`
open Boolean	`removeLastOccurrence(o: Any?)`
open Boolean	`retainAll(elements: Collection<E>)`
open Spliterator<E>	`spliterator()` Returns a `Spliterator` over the elements in this deque.
open E	`take()`
open E	`takeFirst()`
open E	`takeLast()`
open Array<Any!>	`toArray()` 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; the runtime type of the returned array is that of the specified array.
open String	`toString()`

Properties
open Int	`size` Returns the number of elements in this deque.

Public constructors

LinkedBlockingDeque

Added in API level 9

LinkedBlockingDeque()

Creates a LinkedBlockingDeque with a capacity of Integer.MAX_VALUE.

LinkedBlockingDeque

Added in API level 9

LinkedBlockingDeque(capacity: Int)

Creates a LinkedBlockingDeque with the given (fixed) capacity.

Parameters
`capacity`	Int: the capacity of this deque

Exceptions
`java.lang.IllegalArgumentException`	if `capacity` is less than 1

LinkedBlockingDeque

Added in API level 9

LinkedBlockingDeque(c: MutableCollection<out E>!)

Creates a LinkedBlockingDeque with a capacity of Integer.MAX_VALUE, 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 9

open fun add(element: E): Boolean

Inserts the specified element at the end of this deque unless it would violate capacity restrictions. When using a capacity-restricted deque, it is generally preferable to use method #offer(java.lang.Object).

This method is equivalent to #addLast.

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 this deque is full

addAll

Added in API level 9

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 this deque is full

See Also

addFirst

Added in API level 9

open fun addFirst(e: E): Unit

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 this deque is full
`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 9

open fun addLast(e: E): Unit

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 this deque is full
`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 9

open fun clear(): Unit

Atomically 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

contains

Added in API level 9

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 (optional)
`java.lang.NullPointerException`	if the specified element is null (optional)

descendingIterator

Added in API level 9

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

drainTo

Added in API level 9

open fun drainTo(c: MutableCollection<in E>!): Int

Parameters
`c`	MutableCollection<in E>!: the collection to transfer elements into

Return
`Int`	the number of elements transferred

Exceptions
`java.lang.UnsupportedOperationException`	if addition of elements is not supported by the specified collection
`java.lang.ClassCastException`	if the class of an element of this queue prevents it from being added to the specified collection
`java.lang.NullPointerException`	if the specified collection is null
`java.lang.IllegalArgumentException`	if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collection

drainTo

Added in API level 9

open fun drainTo(
    c: MutableCollection<in E>!, 
    maxElements: Int
): Int

Parameters
`c`	MutableCollection<in E>!: the collection to transfer elements into
`maxElements`	Int: the maximum number of elements to transfer

Return
`Int`	the number of elements transferred

Exceptions
`java.lang.UnsupportedOperationException`	if addition of elements is not supported by the specified collection
`java.lang.ClassCastException`	if the class of an element of this queue prevents it from being added to the specified collection
`java.lang.NullPointerException`	if the specified collection is null
`java.lang.IllegalArgumentException`	if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collection

element

Added in API level 9

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

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 9

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 9

open fun getLast(): E

Return
`E`	the tail of this deque

Exceptions
`java.util.NoSuchElementException`	if this deque is empty

iterator

Added in API level 9

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 9

open fun offer(e: E): Boolean

Parameters
`e`	E: the element to add

Return
`Boolean`	`true` if the element was added to this queue, else `false`

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

offer

Added in API level 9

open fun offer(
    e: E, 
    timeout: Long, 
    unit: TimeUnit!
): Boolean

Parameters
`e`	E: the element to add
`timeout`	Long: how long to wait before giving up, in units of `unit`
`unit`	TimeUnit!: a `TimeUnit` determining how to interpret the `timeout` parameter

Return
`Boolean`	`true` if the element was added to this deque, else `false`

Exceptions
`java.lang.InterruptedException`	if interrupted while waiting
`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 9

open fun offerFirst(e: E): Boolean

Parameters
`e`	E: the element to add

Return
`Boolean`	`true` if the element was added to this deque, else `false`

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 9

open fun offerFirst(
    e: E, 
    timeout: Long, 
    unit: TimeUnit!
): Boolean

Parameters
`e`	E: the element to add
`timeout`	Long: how long to wait before giving up, in units of `unit`
`unit`	TimeUnit!: a `TimeUnit` determining how to interpret the `timeout` parameter

Return
`Boolean`	`true` if successful, or `false` if the specified waiting time elapses before space is available

Exceptions
`java.lang.InterruptedException`	if interrupted while waiting
`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 9

open fun offerLast(e: E): Boolean

Parameters
`e`	E: the element to add

Return
`Boolean`	`true` if the element was added to this deque, else `false`

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 9

open fun offerLast(
    e: E, 
    timeout: Long, 
    unit: TimeUnit!
): Boolean

Parameters
`e`	E: the element to add
`timeout`	Long: how long to wait before giving up, in units of `unit`
`unit`	TimeUnit!: a `TimeUnit` determining how to interpret the `timeout` parameter

Return
`Boolean`	`true` if successful, or `false` if the specified waiting time elapses before space is available

Exceptions
`java.lang.InterruptedException`	if interrupted while waiting
`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 9

open fun peek(): E?

Return
`E?`	the head of this deque, or `null` if this deque is empty

peekFirst

Added in API level 9

open fun peekFirst(): E?

Return
`E?`	the head of this deque, or `null` if this deque is empty

peekLast

Added in API level 9

open fun peekLast(): E?

Return
`E?`	the tail of this deque, or `null` if this deque is empty

poll

Added in API level 9

open fun poll(): E?

Return
`E?`	the head of this deque, or `null` if this deque is empty

poll

Added in API level 9

open fun poll(
    timeout: Long, 
    unit: TimeUnit!
): E

Parameters
`timeout`	Long: how long to wait before giving up, in units of `unit`
`unit`	TimeUnit!: a `TimeUnit` determining how to interpret the `timeout` parameter

Return
`E`	the head of this deque, or `null` if the specified waiting time elapses before an element is available

Exceptions
`java.lang.InterruptedException`	if interrupted while waiting

pollFirst

Added in API level 9

open fun pollFirst(): E?

Return
`E?`	the head of this deque, or `null` if this deque is empty

pollFirst

Added in API level 9

open fun pollFirst(
    timeout: Long, 
    unit: TimeUnit!
): E

Parameters
`timeout`	Long: how long to wait before giving up, in units of `unit`
`unit`	TimeUnit!: a `TimeUnit` determining how to interpret the `timeout` parameter

Return
`E`	the head of this deque, or `null` if the specified waiting time elapses before an element is available

Exceptions
`java.lang.InterruptedException`	if interrupted while waiting

pollLast

Added in API level 9

open fun pollLast(): E?

Return
`E?`	the tail of this deque, or `null` if this deque is empty

pollLast

Added in API level 9

open fun pollLast(
    timeout: Long, 
    unit: TimeUnit!
): E

Parameters
`timeout`	Long: how long to wait before giving up, in units of `unit`
`unit`	TimeUnit!: a `TimeUnit` determining how to interpret the `timeout` parameter

Return
`E`	the tail of this deque, or `null` if the specified waiting time elapses before an element is available

Exceptions
`java.lang.InterruptedException`	if interrupted while waiting

pop

Added in API level 9

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 9

open fun push(e: E): Unit

Parameters
`e`	E: the element to push

Exceptions
`java.lang.IllegalStateException`	if this deque is full
`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

put

Added in API level 9

open fun put(e: E): Unit

Parameters
`e`	E: the element to add

Exceptions
`java.lang.InterruptedException`	if interrupted while waiting
`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

putFirst

Added in API level 9

open fun putFirst(e: E): Unit

Parameters
`e`	E: the element to add

Exceptions
`java.lang.InterruptedException`	if interrupted while waiting
`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

putLast

Added in API level 9

open fun putLast(e: E): Unit

Parameters
`e`	E: the element to add

Exceptions
`java.lang.InterruptedException`	if interrupted while waiting
`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

remainingCapacity

Added in API level 9

open fun remainingCapacity(): Int

Returns the number of additional elements that this deque can ideally (in the absence of memory or resource constraints) accept without blocking. This is always equal to the initial capacity of this deque less the current size of this deque.

Note that you cannot always tell if an attempt to insert an element will succeed by inspecting remainingCapacity because it may be the case that another thread is about to insert or remove an element.

Return
`Int`	the remaining capacity

remove

Added in API level 9

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

Added in API level 9

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 this deque changed as a result of the call

Exceptions
`java.lang.ClassCastException`	if the class of the specified element is incompatible with this deque (optional)
`java.lang.NullPointerException`	if the specified element is null (optional)
`java.lang.UnsupportedOperationException`	if the `remove` operation is not supported by this collection

removeAll

Added in API level 9

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

Added in API level 9

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 9

open fun removeFirstOccurrence(o: Any?): Boolean

Parameters
`o`	Any?: element to be removed from this deque, if present

Return
`Boolean`	`true` if an element was removed as a result of this call

Exceptions
`java.lang.ClassCastException`	if the class of the specified element is incompatible with this deque (optional)
`java.lang.NullPointerException`	if the specified element is null (optional)

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 9

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 9

open fun removeLastOccurrence(o: Any?): Boolean

Parameters
`o`	Any?: element to be removed from this deque, if present

Return
`Boolean`	`true` if an element was removed as a result of this call

Exceptions
`java.lang.ClassCastException`	if the class of the specified element is incompatible with this deque (optional)
`java.lang.NullPointerException`	if the specified element is null (optional)

retainAll

Added in API level 9

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

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

take

Added in API level 9

open fun take(): E

Return
`E`	the head of this deque

Exceptions
`java.lang.InterruptedException`	if interrupted while waiting

takeFirst

Added in API level 9

open fun takeFirst(): E

Return
`E`	the head of this deque

Exceptions
`java.lang.InterruptedException`	if interrupted while waiting

takeLast

Added in API level 9

open fun takeLast(): E

Return
`E`	the tail of this deque

Exceptions
`java.lang.InterruptedException`	if interrupted while waiting

toArray

Added in API level 9

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 9

open fun <T : Any!> toArray(a: Array<T>): Array<T>

Returns an array containing all of the elements in this deque, in proper sequence; 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 9

open fun toString(): String

Return
`String`	a string representation of the object.

Properties

size

Added in API level 9

open val size: Int

Returns the number of elements in this deque.

Return
`Int`	the number of elements in this deque