Set to array kotlin

Преобразование списка в массив в Kotlin

В этой статье рассматриваются различные способы преобразования списка в массив в Kotlin.

1. Использование toTypedArray() функция

List интерфейс обеспечивает toTypedArray() функция, которая возвращает типизированный массив, содержащий элементы списка.

Для преобразования между двумя типами вы можете использовать map() функция. Например, следующий код преобразует список целых чисел в массив строк:

2. Использование потока Java 8

Вы также можете использовать Stream для преобразования списка в массив. Хитрость заключается в том, чтобы преобразовать данный список в поток, используя stream() функционировать и использовать toArray() функция для возврата массива, содержащего элементы Stream. Преобразование между двумя типами можно выполнить с помощью лямбда-выражения.

Вот и все о преобразовании списка в массив в Kotlin.

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Convert a Set to a List in Kotlin

This article explores different ways to convert a set to a list using Kotlin.

1. Using toList() function

The standard way to convert a set to a list is using the toList() function.

It returns an immutable list instance. To get a mutable list, you can use the toMutableList() function.

2. Using Copy Constructor

We can use a copy constructor, which can take another collection object to construct a new list containing all elements of the specified set.

3. Using Spread Operator

You can also use the listOf() function using the Spread operator by prefixing its array implementation with * .

4. Using for loop

Another solution is to create an empty list and push every element of the specified Set into the list.

5. Using addAll() function

Instead of using the for-loop, you can use the addAll() to add all elements of the specified Set to the list.

That’s all about converting a set to a list in Kotlin.

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Set to array kotlin

A generic unordered collection of elements that does not support duplicate elements. Methods in this interface support only read-only access to the set; read/write access is supported through the MutableSet interface.

Parameters

E — the type of elements contained in the set. The set is covariant in its element type.

Properties

size

Returns the size of the collection.

Functions

contains

Checks if the specified element is contained in this collection.

containsAll

Checks if all elements in the specified collection are contained in this collection.

isEmpty

Returns true if the collection is empty (contains no elements), false otherwise.

iterator

Returns an iterator over the elements of this object.

Extension Properties

indices

Returns an IntRange of the valid indices for this collection.

Extension Functions

all

Returns true if all elements match the given predicate.

any

Returns true if collection has at least one element.

Returns true if at least one element matches the given predicate.

asIterable

Returns this collection as an Iterable.

asSequence

Creates a Sequence instance that wraps the original collection returning its elements when being iterated.

associate

Returns a Map containing key-value pairs provided by transform function applied to elements of the given collection.

associateBy

Returns a Map containing the elements from the given collection indexed by the key returned from keySelector function applied to each element.

Returns a Map containing the values provided by valueTransform and indexed by keySelector functions applied to elements of the given collection.

associateByTo

Populates and returns the destination mutable map with key-value pairs, where key is provided by the keySelector function applied to each element of the given collection and value is the element itself.

Populates and returns the destination mutable map with key-value pairs, where key is provided by the keySelector function and and value is provided by the valueTransform function applied to elements of the given collection.

fun < T , K , V , M : MutableMap < in K , in V >> Iterable < T >. associateByTo (
destination : M ,
keySelector : ( T ) -> K ,
valueTransform : ( T ) -> V
) : M

associateTo

Populates and returns the destination mutable map with key-value pairs provided by transform function applied to each element of the given collection.

associateWith

Returns a Map where keys are elements from the given collection and values are produced by the valueSelector function applied to each element.

associateWithTo

Populates and returns the destination mutable map with key-value pairs for each element of the given collection, where key is the element itself and value is provided by the valueSelector function applied to that key.

chunked

Splits this collection into a list of lists each not exceeding the given size.

Splits this collection into several lists each not exceeding the given size and applies the given transform function to an each.

contains

Returns true if element is found in the collection.

containsAll

Checks if all elements in the specified collection are contained in this collection.

count

Returns the number of elements matching the given predicate.

distinct

Returns a list containing only distinct elements from the given collection.

distinctBy

Returns a list containing only elements from the given collection having distinct keys returned by the given selector function.

drop

Returns a list containing all elements except first n elements.

dropWhile

Returns a list containing all elements except first elements that satisfy the given predicate.

elementAt

Returns an element at the given index or throws an IndexOutOfBoundsException if the index is out of bounds of this collection.

elementAtOrElse

Returns an element at the given index or the result of calling the defaultValue function if the index is out of bounds of this collection.

elementAtOrNull

Returns an element at the given index or null if the index is out of bounds of this collection.

filter

Returns a list containing only elements matching the given predicate.

filterIndexed

Returns a list containing only elements matching the given predicate.

filterIndexedTo

Appends all elements matching the given predicate to the given destination.

fun < T , C : MutableCollection < in T >> Iterable < T >. filterIndexedTo (
destination : C ,
predicate : ( index : Int , T ) -> Boolean
) : C

filterIsInstance

Returns a list containing all elements that are instances of specified type parameter R.

Returns a list containing all elements that are instances of specified class.

filterIsInstanceTo

Appends all elements that are instances of specified type parameter R to the given destination.

Appends all elements that are instances of specified class to the given destination.

filterNot

Returns a list containing all elements not matching the given predicate.

filterNotNull

Returns a list containing all elements that are not null .

filterNotNullTo

Appends all elements that are not null to the given destination.

filterNotTo

Appends all elements not matching the given predicate to the given destination.

fun < T , C : MutableCollection < in T >> Iterable < T >. filterNotTo (
destination : C ,
predicate : ( T ) -> Boolean
) : C

filterTo

Appends all elements matching the given predicate to the given destination.

find

Returns the first element matching the given predicate, or null if no such element was found.

findLast

Returns the last element matching the given predicate, or null if no such element was found.

first

Returns the first element.

Returns the first element matching the given predicate.

firstNotNullOf

Returns the first non-null value produced by transform function being applied to elements of this collection in iteration order, or throws NoSuchElementException if no non-null value was produced.

firstNotNullOfOrNull

Returns the first non-null value produced by transform function being applied to elements of this collection in iteration order, or null if no non-null value was produced.

firstOrNull

Returns the first element, or null if the collection is empty.

Returns the first element matching the given predicate, or null if element was not found.

flatMap

Returns a single list of all elements yielded from results of transform function being invoked on each element of original collection.

flatMapIndexed

Returns a single list of all elements yielded from results of transform function being invoked on each element and its index in the original collection.

flatMapIndexedTo

Appends all elements yielded from results of transform function being invoked on each element and its index in the original collection, to the given destination.

fun < T , R , C : MutableCollection < in R >> Iterable < T >. flatMapIndexedTo (
destination : C ,
transform : ( index : Int , T ) -> Iterable < R >
) : C

fun < T , R , C : MutableCollection < in R >> Iterable < T >. flatMapIndexedTo (
destination : C ,
transform : ( index : Int , T ) -> Sequence < R >
) : C

flatMapTo

Appends all elements yielded from results of transform function being invoked on each element of original collection, to the given destination.

flatten

Returns a single list of all elements from all collections in the given collection.

fold

Accumulates value starting with initial value and applying operation from left to right to current accumulator value and each element.

foldIndexed

Accumulates value starting with initial value and applying operation from left to right to current accumulator value and each element with its index in the original collection.

forEach

Performs the given action on each element.

forEachIndexed

Performs the given action on each element, providing sequential index with the element.

groupBy

Groups elements of the original collection by the key returned by the given keySelector function applied to each element and returns a map where each group key is associated with a list of corresponding elements.

Groups values returned by the valueTransform function applied to each element of the original collection by the key returned by the given keySelector function applied to the element and returns a map where each group key is associated with a list of corresponding values.

groupByTo

Groups elements of the original collection by the key returned by the given keySelector function applied to each element and puts to the destination map each group key associated with a list of corresponding elements.

Groups values returned by the valueTransform function applied to each element of the original collection by the key returned by the given keySelector function applied to the element and puts to the destination map each group key associated with a list of corresponding values.

fun < T , K , V , M : MutableMap < in K , MutableList < V >> > Iterable < T >. groupByTo (
destination : M ,
keySelector : ( T ) -> K ,
valueTransform : ( T ) -> V
) : M

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