Added in API level 1

LinkedList

open class LinkedList<E : Any!> : AbstractSequentialList<E>, Deque<E>, Cloneable, Serializable, MutableList<E>
kotlin.Any
   ↳ java.util.AbstractCollection<E>
   ↳ java.util.AbstractList<E>
   ↳ java.util.AbstractSequentialList<E>
   ↳ java.util.LinkedList

Doubly-linked list implementation of the List and Deque interfaces. Implements all optional list operations, and permits all elements (including null).

All of the operations perform as could be expected for a doubly-linked list. Operations that index into the list will traverse the list from the beginning or the end, whichever is closer to the specified index.

Note that this implementation is not synchronized. If multiple threads access a linked list concurrently, and at least one of the threads modifies the list structurally, it must be synchronized externally. (A structural modification is any operation that adds or deletes one or more elements; merely setting the value of an element is not a structural modification.) This is typically accomplished by synchronizing on some object that naturally encapsulates the list. If no such object exists, the list should be "wrapped" using the Collections.synchronizedList method. This is best done at creation time, to prevent accidental unsynchronized access to the list:

List list = Collections.synchronizedList(new LinkedList(...));

The iterators returned by this class's iterator and listIterator methods are fail-fast: if the list is structurally modified at any time after the iterator is created, in any way except through the Iterator's own remove or add methods, the iterator will 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 is a member of the Java Collections Framework.

Summary

Public constructors

Constructs an empty list.

Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.

Public methods
open Boolean
add(element: E)

Appends the specified element to the end of this list.

open Unit
add(index: Int, element: E)

Inserts the specified element at the specified position in this list.

open Boolean
addAll(elements: Collection<E>)

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

open Boolean
addAll(index: Int, elements: Collection<E>)

Inserts all of the elements in the specified collection into this list, starting at the specified position.

open Unit
addFirst(e: E)

Inserts the specified element at the beginning of this list.

open Unit
addLast(e: E)

Appends the specified element to the end of this list.

open Unit

Removes all of the elements from this list.

open Any

Returns a shallow copy of this LinkedList.

open Boolean
contains(element: E)

Returns true if this list contains the specified element.

open Boolean
contains(element: E)

Returns true if this list contains the specified element.

open MutableIterator<E>

open E

Retrieves, but does not remove, the head (first element) of this list.

open E
get(index: Int)

Returns the element at the specified position in this list.

open E

Returns the first element in this list.

open E

Returns the last element in this list.

open Int
indexOf(element: E)

Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.

open Int
indexOf(element: E)

Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.

open Int
lastIndexOf(element: E)

Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.

open Int
lastIndexOf(element: E)

Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.

open MutableListIterator<E>
listIterator(index: Int)

Returns a list-iterator of the elements in this list (in proper sequence), starting at the specified position in the list.

open Boolean
offer(e: E)

Adds the specified element as the tail (last element) of this list.

open Boolean
offerFirst(e: E)

Inserts the specified element at the front of this list.

open Boolean
offerLast(e: E)

Inserts the specified element at the end of this list.

open E?

Retrieves, but does not remove, the head (first element) of this list.

open E?

Retrieves, but does not remove, the first element of this list, or returns null if this list is empty.

open E?

Retrieves, but does not remove, the last element of this list, or returns null if this list is empty.

open E?

Retrieves and removes the head (first element) of this list.

open E?

Retrieves and removes the first element of this list, or returns null if this list is empty.

open E?

Retrieves and removes the last element of this list, or returns null if this list is empty.

open E
pop()

Pops an element from the stack represented by this list.

open Unit
push(e: E)

Pushes an element onto the stack represented by this list.

open E

Retrieves and removes the head (first element) of this list.

open Boolean
remove(element: E)

Removes the first occurrence of the specified element from this list, if it is present.

open Boolean
remove(element: E)

Removes the first occurrence of the specified element from this list, if it is present.

open E
removeAt(index: Int)

Removes the element at the specified position in this list.

open E

Removes and returns the first element from this list.

open Boolean

Removes the first occurrence of the specified element in this list (when traversing the list from head to tail).

open E

Removes and returns the last element from this list.

open Boolean

Removes the last occurrence of the specified element in this list (when traversing the list from head to tail).

open LinkedList<E>

Returns a reverse-ordered view of this collection.

open E
set(index: Int, element: E)

Replaces the element at the specified position in this list with the specified element.

open Spliterator<E>

Creates a late-binding and fail-fast Spliterator over the elements in this list.

open Array<Any!>

Returns an array containing all of the elements in this list 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 list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array.

Inherited functions
Properties
open Int

Returns the number of elements in this list.

Inherited properties

Public constructors

LinkedList

Added in API level 1
LinkedList()

Constructs an empty list.

LinkedList

Added in API level 1
LinkedList(c: MutableCollection<out E>)

Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.

Parameters
c MutableCollection<out E>: the collection whose elements are to be placed into this list
Exceptions
java.lang.NullPointerException if the specified collection is null

Public methods

add

Added in API level 1
open fun add(element: E): Boolean

Appends the specified element to the end of this list.

This method is equivalent to #addLast.

Parameters
e element to be appended to this list
Return
Boolean true (as specified by Collection#add)
Exceptions
java.lang.UnsupportedOperationException if the add operation is not supported by this list
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
java.lang.IllegalStateException if the element cannot be added at this time due to capacity restrictions

add

Added in API level 1
open fun add(
    index: Int,
    element: E
): Unit

Inserts the specified element at the specified position in this list. Shifts the element currently at that position (if any) and any subsequent elements to the right (adds one to their indices).

Parameters
index Int: index at which the specified element is to be inserted
element E: element to be inserted
Exceptions
java.lang.UnsupportedOperationException if the add operation is not supported by this list
java.lang.ClassCastException if the class of the specified element prevents it from being added to this list
java.lang.NullPointerException if the specified element is null and this list does not permit null elements
java.lang.IllegalArgumentException if some property of the specified element prevents it from being added to this list
java.lang.IndexOutOfBoundsException if the index is out of range (index < 0 || index > size())

addAll

Added in API level 1
open fun addAll(elements: Collection<E>): Boolean

Appends all of the elements in the specified collection to the end of this list, in the order that they are returned by the specified collection's iterator. The behavior of this operation is undefined if the specified collection is modified while the operation is in progress. (Note that this will occur if the specified collection is this list, and it's nonempty.)

Parameters
c collection containing elements to be added to this list
Return
Boolean true if this list changed as a result of the call
Exceptions
java.lang.UnsupportedOperationException if the addAll operation is not supported by this list
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 is 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

addAll

Added in API level 1
open fun addAll(
    index: Int,
    elements: Collection<E>
): Boolean

Inserts all of the elements in the specified collection into this list, starting at the specified position. Shifts the element currently at that position (if any) and any subsequent elements to the right (increases their indices). The new elements will appear in the list in the order that they are returned by the specified collection's iterator.

Parameters
index Int: index at which to insert the first element from the specified collection
c collection containing elements to be added to this list
Return
Boolean true if this list changed as a result of the call
Exceptions
java.lang.UnsupportedOperationException if the addAll operation is not supported by this list
java.lang.ClassCastException if the class of an element of the specified collection prevents it from being added to this list
java.lang.NullPointerException if the specified collection is null
java.lang.IllegalArgumentException if some property of an element of the specified collection prevents it from being added to this list
java.lang.IndexOutOfBoundsException if the index is out of range (index < 0 || index > size())

addFirst

Added in API level 1
open fun addFirst(e: E): Unit

Inserts the specified element at the beginning of this list.

Parameters
e E: the element to add
Exceptions
java.lang.NullPointerException if the specified element is null and this deque does not permit null elements
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 1
open fun addLast(e: E): Unit

Appends the specified element to the end of this list.

This method is equivalent to #add.

Parameters
e E: the element to add
Exceptions
java.lang.NullPointerException if the specified element is null and this deque does not permit null elements
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 1
open fun clear(): Unit

Removes all of the elements from this list. The list will be empty after this call returns.

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

clone

Added in API level 1
open fun clone(): Any

Returns a shallow copy of this LinkedList. (The elements themselves are not cloned.)

Return
Any a shallow copy of this LinkedList instance
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

Added in API level 1
open fun contains(element: E): Boolean

Returns true if this list contains the specified element. More formally, returns true if and only if this list contains at least one element e such that Objects.equals(o, e).

Parameters
o element whose presence in this list is to be tested
Return
Boolean true if this list 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#)

contains

Added in API level 1
open fun contains(element: E): Boolean

Returns true if this list contains the specified element. More formally, returns true if and only if this list contains at least one element e such that Objects.equals(o, e).

Parameters
o element whose presence in this list is to be tested
Return
Boolean true if this list 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 9
open fun descendingIterator(): MutableIterator<E>
Return
MutableIterator<E> an iterator over the elements in this deque in reverse sequence

element

Added in API level 1
open fun element(): E

Retrieves, but does not remove, the head (first element) of this list.

Return
E the head of this list
Exceptions
java.util.NoSuchElementException if this list is empty

get

Added in API level 1
open fun get(index: Int): E

Returns the element at the specified position in this list.

Parameters
index Int: index of the element to return
Return
E the element at the specified position in this list
Exceptions
java.lang.IndexOutOfBoundsException if the index is out of range (index < 0 || index >= size())

getFirst

Added in API level 1
open fun getFirst(): E

Returns the first element in this list.

Return
E the first element in this list
Exceptions
java.util.NoSuchElementException if this list is empty

getLast

Added in API level 1
open fun getLast(): E

Returns the last element in this list.

Return
E the last element in this list
Exceptions
java.util.NoSuchElementException if this list is empty

indexOf

Added in API level 1
open fun indexOf(element: E): Int

Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element. More formally, returns the lowest index i such that Objects.equals(o, get(i)), or -1 if there is no such index.

Parameters
o element to search for
Return
Int the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element
Exceptions
java.lang.ClassCastException if the type of the specified element is incompatible with this list (optional)
java.lang.NullPointerException if the specified element is null and this list does not permit null elements (optional)

indexOf

Added in API level 1
open fun indexOf(element: E): Int

Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element. More formally, returns the lowest index i such that Objects.equals(o, get(i)), or -1 if there is no such index.

Parameters
o element to search for
Return
Int the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element
Exceptions
java.lang.ClassCastException if the type of the specified element is incompatible with this list (optional)
java.lang.NullPointerException if the specified element is null and this list does not permit null elements (optional)

lastIndexOf

Added in API level 1
open fun lastIndexOf(element: E): Int

Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element. More formally, returns the highest index i such that Objects.equals(o, get(i)), or -1 if there is no such index.

Parameters
o element to search for
Return
Int the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element
Exceptions
java.lang.ClassCastException if the type of the specified element is incompatible with this list (optional)
java.lang.NullPointerException if the specified element is null and this list does not permit null elements (optional)

lastIndexOf

Added in API level 1
open fun lastIndexOf(element: E): Int

Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element. More formally, returns the highest index i such that Objects.equals(o, get(i)), or -1 if there is no such index.

Parameters
o element to search for
Return
Int the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element
Exceptions
java.lang.ClassCastException if the type of the specified element is incompatible with this list (optional)
java.lang.NullPointerException if the specified element is null and this list does not permit null elements (optional)

listIterator

Added in API level 1
open fun listIterator(index: Int): MutableListIterator<E>

Returns a list-iterator of the elements in this list (in proper sequence), starting at the specified position in the list. Obeys the general contract of List.listIterator(int).

The list-iterator is fail-fast: if the list is structurally modified at any time after the Iterator is created, in any way except through the list-iterator's own remove or add methods, the list-iterator will 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.

Parameters
index Int: index of the first element to be returned from the list-iterator (by a call to next)
Return
MutableListIterator<E> a ListIterator of the elements in this list (in proper sequence), starting at the specified position in the list
Exceptions
java.lang.IndexOutOfBoundsException if the index is out of range (index < 0 || index > size())

offer

Added in API level 1
open fun offer(e: E): Boolean

Adds the specified element as the tail (last element) of this list.

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 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

offerFirst

Added in API level 9
open fun offerFirst(e: E): Boolean

Inserts the specified element at the front of this list.

Parameters
e E: the element to insert
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 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

offerLast

Added in API level 9
open fun offerLast(e: E): Boolean

Inserts the specified element at the end of this list.

Parameters
e E: the element to insert
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 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

peek

Added in API level 1
open fun peek(): E?

Retrieves, but does not remove, the head (first element) of this list.

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

peekFirst

Added in API level 9
open fun peekFirst(): E?

Retrieves, but does not remove, the first element of this list, or returns null if this list is empty.

Return
E? the first element of this list, or null if this list is empty

peekLast

Added in API level 9
open fun peekLast(): E?

Retrieves, but does not remove, the last element of this list, or returns null if this list is empty.

Return
E? the last element of this list, or null if this list is empty

poll

Added in API level 1
open fun poll(): E?

Retrieves and removes the head (first element) of this list.

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

pollFirst

Added in API level 9
open fun pollFirst(): E?

Retrieves and removes the first element of this list, or returns null if this list is empty.

Return
E? the first element of this list, or null if this list is empty

pollLast

Added in API level 9
open fun pollLast(): E?

Retrieves and removes the last element of this list, or returns null if this list is empty.

Return
E? the last element of this list, or null if this list is empty

pop

Added in API level 9
open fun pop(): E

Pops an element from the stack represented by this list. In other words, removes and returns the first element of this list.

This method is equivalent to #removeFirst().

Return
E the element at the front of this list (which is the top of the stack represented by this list)
Exceptions
java.util.NoSuchElementException if this list is empty

push

Added in API level 9
open fun push(e: E): Unit

Pushes an element onto the stack represented by this list. In other words, inserts the element at the front of this list.

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 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 1
open fun remove(): E

Retrieves and removes the head (first element) of this list.

Return
E the head of this list
Exceptions
java.util.NoSuchElementException if this list is empty

remove

Added in API level 1
open fun remove(element: E): Boolean

Removes the first occurrence of the specified element from this list, if it is present. If this list does not contain the element, it is unchanged. More formally, removes the element with the lowest index i such that Objects.equals(o, get(i)) (if such an element exists). Returns true if this list contained the specified element (or equivalently, if this list changed as a result of the call).

Parameters
o element to be removed from this list, if present
Return
Boolean true if this list 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 list

remove

Added in API level 1
open fun remove(element: E): Boolean

Removes the first occurrence of the specified element from this list, if it is present. If this list does not contain the element, it is unchanged. More formally, removes the element with the lowest index i such that Objects.equals(o, get(i)) (if such an element exists). Returns true if this list contained the specified element (or equivalently, if this list changed as a result of the call).

Parameters
o element to be removed from this list, if present
Return
Boolean true if this list 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 list

removeAt

Added in API level 1
open fun removeAt(index: Int): E

Removes the element at the specified position in this list. Shifts any subsequent elements to the left (subtracts one from their indices). Returns the element that was removed from the list.

Parameters
index Int: the index of the element to be removed
Return
E the element previously at the specified position
Exceptions
java.lang.UnsupportedOperationException if the remove operation is not supported by this list
java.lang.IndexOutOfBoundsException if the index is out of range (index < 0 || index >= size())

removeFirst

Added in API level 1
open fun removeFirst(): E

Removes and returns the first element from this list.

Return
E the first element from this list
Exceptions
java.util.NoSuchElementException if this list 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

Removes the first occurrence of the specified element in this list (when traversing the list from head to tail). If the list does not contain the element, it is unchanged.

Parameters
o Any?: element to be removed from this list, if present
Return
Boolean true if the list 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#)

removeLast

Added in API level 1
open fun removeLast(): E

Removes and returns the last element from this list.

Return
E the last element from this list
Exceptions
java.util.NoSuchElementException if this list 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

Removes the last occurrence of the specified element in this list (when traversing the list from head to tail). If the list does not contain the element, it is unchanged.

Parameters
o Any?: element to be removed from this list, if present
Return
Boolean true if the list 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#)

reversed

Added in API level 35
open fun reversed(): LinkedList<E>

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.

Modifications to the reversed view are permitted and will be propagated to this list. In addition, modifications to this list will be visible in the reversed view.

Return
LinkedList<E> a reverse-ordered view of this collection, as a List

set

Added in API level 1
open fun set(
    index: Int,
    element: E
): E

Replaces the element at the specified position in this list with the specified element.

Parameters
index Int: index of the element to replace
element E: element to be stored at the specified position
Return
E the element previously at the specified position
Exceptions
java.lang.UnsupportedOperationException if the set operation is not supported by this list
java.lang.ClassCastException if the class of the specified element prevents it from being added to this list
java.lang.NullPointerException if the specified element is null and this list does not permit null elements
java.lang.IllegalArgumentException if some property of the specified element prevents it from being added to this list
java.lang.IndexOutOfBoundsException if the index is out of range (index < 0 || index >= size())

spliterator

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

Creates a late-binding and fail-fast Spliterator over the elements in this list.

The Spliterator reports Spliterator#SIZED and Spliterator#ORDERED. Overriding implementations should document the reporting of additional characteristic values.

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

toArray

Added in API level 1
open fun toArray(): Array<Any!>

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

The returned array will be "safe" in that no references to it are maintained by this list. (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 list in proper sequence

toArray

Added in API level 1
open fun <T : Any!> toArray(a: Array<T>): Array<T>

Returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array. If the list 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 list.

If the list fits in the specified array with room to spare (i.e., the array has more elements than the list), the element in the array immediately following the end of the list is set to null. (This is useful in determining the length of the list only if the caller knows that the list does not contain any null elements.)

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 list known to contain only strings. The following code can be used to dump the list into a newly allocated array of String:

String[] y = x.toArray(new String[0]);
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 list 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 the elements of the list
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 list
java.lang.NullPointerException if the specified array is null

Properties

size

Added in API level 1
open val size: Int

Returns the number of elements in this list.

Return
Int the number of elements in this list