kotlin-stdlib/kotlin.collections/Collection

Collection

interface Collection<out E> : Iterable<E> (source)

A generic collection of elements. Methods in this interface support only read-only access to the collection; read/write access is supported through the MutableCollection interface.

Since Kotlin

1.0

Parameters

E

the type of elements contained in the collection. The collection is covariant in its element type.

Inheritors

MutableCollection

AbstractCollection

MatchGroupCollection

interface Collection<out E> : Iterable<E> (source)

A generic collection of elements. Methods in this interface support only read-only access to the collection; read/write access is supported through the MutableCollection interface.

Since Kotlin

1.1

Parameters

E

the type of elements contained in the collection. The collection is covariant in its element type.

Inheritors

MutableCollection

interface Collection<out E> : Iterable<E> (source)

A generic collection of elements. Methods in this interface support only read-only access to the collection; read/write access is supported through the MutableCollection interface.

Since Kotlin

1.3

Parameters

E

the type of elements contained in the collection. The collection is covariant in its element type.

Inheritors

MutableCollection

interface Collection<out E> : Iterable<E> (source)

A generic collection of elements. Methods in this interface support only read-only access to the collection; read/write access is supported through the MutableCollection interface.

Since Kotlin

1.8

Parameters

E

the type of elements contained in the collection. The collection is covariant in its element type.

Inheritors

MutableCollection

interface Collection<out E> : Iterable<E> (source)

A generic collection of elements. Methods in this interface support only read-only access to the collection; read/write access is supported through the MutableCollection interface.

Since Kotlin

1.8

Parameters

E

the type of elements contained in the collection. The collection is covariant in its element type.

Inheritors

MutableCollection

Properties

val Collection<*>.indices: IntRange

Returns an IntRange of the valid indices for this collection.

Since Kotlin 1.0

abstract val size: Int

Returns the size of the collection.

Since Kotlin 1.0

abstract val size: Int

Returns the size of the collection.

Since Kotlin 1.1

abstract val size: Int

Returns the size of the collection.

Since Kotlin 1.3

abstract val size: Int

Returns the size of the collection.

Since Kotlin 1.8

abstract val size: Int

Returns the size of the collection.

Since Kotlin 1.8

Functions

inline fun <T> Iterable<T>.all(predicate: (T) -> Boolean): Boolean

Returns true if all elements match the given predicate.

Since Kotlin 1.0

fun <T> Iterable<T>.any(): Boolean

Returns true if collection has at least one element.

Since Kotlin 1.0

inline fun <T> Iterable<T>.any(predicate: (T) -> Boolean): Boolean

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

Since Kotlin 1.0

inline fun <T> Iterable<T>.asIterable(): Iterable<T>

Returns this collection as an Iterable.

Since Kotlin 1.0

fun <T> Iterable<T>.asSequence(): Sequence<T>

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

Since Kotlin 1.0

inline fun <T, K, V> Iterable<T>.associate(transform: (T) -> Pair<K, V>): Map<K, V>

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

Since Kotlin 1.0

inline fun <T, K> Iterable<T>.associateBy(keySelector: (T) -> K): Map<K, T>

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

Since Kotlin 1.0

inline fun <T, K, V> Iterable<T>.associateBy(keySelector: (T) -> K, valueTransform: (T) -> V): Map<K, V>

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

Since Kotlin 1.0

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

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.

Since Kotlin 1.0

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

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.

Since Kotlin 1.0

inline fun <T, K, V, M : MutableMap<in K, in V>> Iterable<T>.associateTo(destination: M, transform: (T) -> Pair<K, V>): M

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

Since Kotlin 1.0

inline fun <K, V> Iterable<K>.associateWith(valueSelector: (K) -> V): Map<K, V>

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

Since Kotlin 1.3

associateWithTo

inline fun <K, V, M : MutableMap<in K, in V>> Iterable<K>.associateWithTo(destination: M, valueSelector: (K) -> V): M

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.

Since Kotlin 1.3

@JvmName(name = "averageOfByte")

fun Iterable<Byte>.average(): Double

@JvmName(name = "averageOfDouble")

fun Iterable<Double>.average(): Double

@JvmName(name = "averageOfFloat")

fun Iterable<Float>.average(): Double

@JvmName(name = "averageOfInt")

fun Iterable<Int>.average(): Double

@JvmName(name = "averageOfLong")

fun Iterable<Long>.average(): Double

@JvmName(name = "averageOfShort")

fun Iterable<Short>.average(): Double

Returns an average value of elements in the collection.

Since Kotlin 1.0

fun <T> Iterable<T>.chunked(size: Int): List<List<T>>

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

Since Kotlin 1.2

fun <T, R> Iterable<T>.chunked(size: Int, transform: (List<T>) -> R): List<R>

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

Since Kotlin 1.2

abstract operator fun contains(element: @UnsafeVariance E): Boolean

Checks if the specified element is contained in this collection.

Since Kotlin 1.0

abstract operator fun contains(element: @UnsafeVariance E): Boolean

Checks if the specified element is contained in this collection.

Since Kotlin 1.1

abstract operator fun contains(element: @UnsafeVariance E): Boolean

Checks if the specified element is contained in this collection.

Since Kotlin 1.3

abstract operator fun contains(element: @UnsafeVariance E): Boolean

Checks if the specified element is contained in this collection.

Since Kotlin 1.8

abstract operator fun contains(element: @UnsafeVariance E): Boolean

Checks if the specified element is contained in this collection.

Since Kotlin 1.8

operator fun <T> Iterable<T>.contains(element: T): Boolean

Returns true if element is found in the collection.

Since Kotlin 1.0

abstract fun containsAll(elements: Collection<@UnsafeVariance E>): Boolean

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

Since Kotlin 1.0

abstract fun containsAll(elements: Collection<@UnsafeVariance E>): Boolean

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

Since Kotlin 1.1

abstract fun containsAll(elements: Collection<@UnsafeVariance E>): Boolean

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

Since Kotlin 1.3

abstract fun containsAll(elements: Collection<@UnsafeVariance E>): Boolean

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

Since Kotlin 1.8

abstract fun containsAll(elements: Collection<@UnsafeVariance E>): Boolean

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

Since Kotlin 1.8

inline fun <T> Collection<T>.containsAll(elements: Collection<T>): Boolean

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

Since Kotlin 1.0

inline fun <T> Collection<T>.count(): Int

fun <T> Iterable<T>.count(): Int

Returns the number of elements in this collection.

Since Kotlin 1.0

inline fun <T> Iterable<T>.count(predicate: (T) -> Boolean): Int

Returns the number of elements matching the given predicate.

Since Kotlin 1.0

fun <T> Iterable<T>.distinct(): List<T>

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

Since Kotlin 1.0

inline fun <T, K> Iterable<T>.distinctBy(selector: (T) -> K): List<T>

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

Since Kotlin 1.0

fun <T> Iterable<T>.drop(n: Int): List<T>

Returns a list containing all elements except first n elements.

Since Kotlin 1.0

inline fun <T> Iterable<T>.dropWhile(predicate: (T) -> Boolean): List<T>

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

Since Kotlin 1.0

fun <T> Iterable<T>.elementAt(index: Int): T

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

Since Kotlin 1.0

elementAtOrElse

fun <T> Iterable<T>.elementAtOrElse(index: Int, defaultValue: (Int) -> T): T

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.

Since Kotlin 1.0

elementAtOrNull

fun <T> Iterable<T>.elementAtOrNull(index: Int): T?

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

Since Kotlin 1.0

inline fun <T> Iterable<T>.filter(predicate: (T) -> Boolean): List<T>

Returns a list containing only elements matching the given predicate.

Since Kotlin 1.0

inline fun <T> Iterable<T>.filterIndexed(predicate: (index: Int, T) -> Boolean): List<T>

Returns a list containing only elements matching the given predicate.

Since Kotlin 1.0

filterIndexedTo

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

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

Since Kotlin 1.0

filterIsInstance

inline fun <R> Iterable<*>.filterIsInstance(): List<R>

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

Since Kotlin 1.0

fun <R> Iterable<*>.filterIsInstance(klass: Class<R>): List<R>

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

Since Kotlin 1.0

filterIsInstanceTo

inline fun <R, C : MutableCollection<in R>> Iterable<*>.filterIsInstanceTo(destination: C): C

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

Since Kotlin 1.0

fun <C : MutableCollection<in R>, R> Iterable<*>.filterIsInstanceTo(destination: C, klass: Class<R>): C

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

Since Kotlin 1.0

inline fun <T> Iterable<T>.filterNot(predicate: (T) -> Boolean): List<T>

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

Since Kotlin 1.0

fun <T : Any> Iterable<T?>.filterNotNull(): List<T>

Returns a list containing all elements that are not null.

Since Kotlin 1.0

filterNotNullTo

fun <C : MutableCollection<in T>, T : Any> Iterable<T?>.filterNotNullTo(destination: C): C

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

Since Kotlin 1.0

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

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

Since Kotlin 1.0

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

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

Since Kotlin 1.0

inline fun <T> Iterable<T>.find(predicate: (T) -> Boolean): T?

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

Since Kotlin 1.0

inline fun <T> Iterable<T>.findLast(predicate: (T) -> Boolean): T?

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

Since Kotlin 1.0

fun <T> Iterable<T>.first(): T

Returns the first element.

Since Kotlin 1.0

inline fun <T> Iterable<T>.first(predicate: (T) -> Boolean): T

Returns the first element matching the given predicate.

Since Kotlin 1.0

inline fun <T, R : Any> Iterable<T>.firstNotNullOf(transform: (T) -> R?): R

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.

Since Kotlin 1.5

firstNotNullOfOrNull

inline fun <T, R : Any> Iterable<T>.firstNotNullOfOrNull(transform: (T) -> R?): R?

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.

Since Kotlin 1.5

fun <T> Iterable<T>.firstOrNull(): T?

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

Since Kotlin 1.0

inline fun <T> Iterable<T>.firstOrNull(predicate: (T) -> Boolean): T?

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

Since Kotlin 1.0

inline fun <T, R> Iterable<T>.flatMap(transform: (T) -> Iterable<R>): List<R>

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

Since Kotlin 1.0

@JvmName(name = "flatMapSequence")

inline fun <T, R> Iterable<T>.flatMap(transform: (T) -> Sequence<R>): List<R>

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

Since Kotlin 1.4

@JvmName(name = "flatMapIndexedIterable")

inline fun <T, R> Iterable<T>.flatMapIndexed(transform: (index: Int, T) -> Iterable<R>): List<R>

@JvmName(name = "flatMapIndexedSequence")

inline fun <T, R> Iterable<T>.flatMapIndexed(transform: (index: Int, T) -> Sequence<R>): List<R>

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.

Since Kotlin 1.4

flatMapIndexedTo

@JvmName(name = "flatMapIndexedIterableTo")

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

@JvmName(name = "flatMapIndexedSequenceTo")

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

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.

Since Kotlin 1.4

inline fun <T, R, C : MutableCollection<in R>> Iterable<T>.flatMapTo(destination: C, transform: (T) -> Iterable<R>): C

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

Since Kotlin 1.0

@JvmName(name = "flatMapSequenceTo")

inline fun <T, R, C : MutableCollection<in R>> Iterable<T>.flatMapTo(destination: C, transform: (T) -> Sequence<R>): C

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

Since Kotlin 1.4

fun <T> Iterable<Iterable<T>>.flatten(): List<T>

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

Since Kotlin 1.0

inline fun <T, R> Iterable<T>.fold(initial: R, operation: (acc: R, T) -> R): R

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

Since Kotlin 1.0

inline fun <T, R> Iterable<T>.foldIndexed(initial: R, operation: (index: Int, acc: R, T) -> R): R

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.

Since Kotlin 1.0

inline fun <T> Iterable<T>.forEach(action: (T) -> Unit)

Performs the given action on each element.

Since Kotlin 1.0

inline fun <T> Iterable<T>.forEachIndexed(action: (index: Int, T) -> Unit)

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

Since Kotlin 1.0

inline fun <T, K> Iterable<T>.groupBy(keySelector: (T) -> K): Map<K, List<T>>

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.

Since Kotlin 1.0

inline fun <T, K, V> Iterable<T>.groupBy(keySelector: (T) -> K, valueTransform: (T) -> V): Map<K, List<V>>

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.

Since Kotlin 1.0

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

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.

Since Kotlin 1.0

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

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.

Since Kotlin 1.0

inline fun <T, K> Iterable<T>.groupingBy(crossinline keySelector: (T) -> K): Grouping<T, K>

Creates a Grouping source from a collection to be used later with one of group-and-fold operations using the specified keySelector function to extract a key from each element.

Since Kotlin 1.1

fun <T> Iterable<T>.indexOf(element: T): Int

Returns first index of element, or -1 if the collection does not contain element.

Since Kotlin 1.0

inline fun <T> Iterable<T>.indexOfFirst(predicate: (T) -> Boolean): Int

Returns index of the first element matching the given predicate, or -1 if the collection does not contain such element.

Since Kotlin 1.0

inline fun <T> Iterable<T>.indexOfLast(predicate: (T) -> Boolean): Int

Returns index of the last element matching the given predicate, or -1 if the collection does not contain such element.

Since Kotlin 1.0

infix fun <T> Iterable<T>.intersect(other: Iterable<T>): Set<T>

Returns a set containing all elements that are contained by both this collection and the specified collection.

Since Kotlin 1.0

abstract fun isEmpty(): Boolean

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

Since Kotlin 1.0

abstract fun isEmpty(): Boolean

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

Since Kotlin 1.1

abstract fun isEmpty(): Boolean

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

Since Kotlin 1.3

abstract fun isEmpty(): Boolean

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

Since Kotlin 1.8

abstract fun isEmpty(): Boolean

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

Since Kotlin 1.8

inline fun <T> Collection<T>.isNotEmpty(): Boolean

Returns true if the collection is not empty.

Since Kotlin 1.0

inline fun <T> Collection<T>?.isNullOrEmpty(): Boolean

Returns true if this nullable collection is either null or empty.

Since Kotlin 1.3

abstract operator override fun iterator(): Iterator<E>

Returns an iterator over the elements of this object.

Since Kotlin 1.0

abstract operator override fun iterator(): Iterator<E>

Returns an iterator over the elements of this object.

Since Kotlin 1.1

abstract operator override fun iterator(): Iterator<E>

Returns an iterator over the elements of this object.

Since Kotlin 1.3

abstract operator override fun iterator(): Iterator<E>

Returns an iterator over the elements of this object.

Since Kotlin 1.8

abstract operator override fun iterator(): Iterator<E>

Returns an iterator over the elements of this object.

Since Kotlin 1.8

fun <T, A : Appendable> Iterable<T>.joinTo(buffer: A, separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: (T) -> CharSequence? = null): A

Appends the string from all the elements separated using separator and using the given prefix and postfix if supplied.

Since Kotlin 1.0

fun <T> Iterable<T>.joinToString(separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: (T) -> CharSequence? = null): String

Creates a string from all the elements separated using separator and using the given prefix and postfix if supplied.

Since Kotlin 1.0

fun <T> Iterable<T>.last(): T

Returns the last element.

Since Kotlin 1.0

inline fun <T> Iterable<T>.last(predicate: (T) -> Boolean): T

Returns the last element matching the given predicate.

Since Kotlin 1.0

fun <T> Iterable<T>.lastIndexOf(element: T): Int

Returns last index of element, or -1 if the collection does not contain element.

Since Kotlin 1.0

fun <T> Iterable<T>.lastOrNull(): T?

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

Since Kotlin 1.0

inline fun <T> Iterable<T>.lastOrNull(predicate: (T) -> Boolean): T?

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

Since Kotlin 1.0

inline fun <T, R> Iterable<T>.map(transform: (T) -> R): List<R>

Returns a list containing the results of applying the given transform function to each element in the original collection.

Since Kotlin 1.0

inline fun <T, R> Iterable<T>.mapIndexed(transform: (index: Int, T) -> R): List<R>

Returns a list containing the results of applying the given transform function to each element and its index in the original collection.

Since Kotlin 1.0

mapIndexedNotNull

inline fun <T, R : Any> Iterable<T>.mapIndexedNotNull(transform: (index: Int, T) -> R?): List<R>

Returns a list containing only the non-null results of applying the given transform function to each element and its index in the original collection.

Since Kotlin 1.0

mapIndexedNotNullTo

inline fun <T, R : Any, C : MutableCollection<in R>> Iterable<T>.mapIndexedNotNullTo(destination: C, transform: (index: Int, T) -> R?): C

Applies the given transform function to each element and its index in the original collection and appends only the non-null results to the given destination.

Since Kotlin 1.0

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

Applies the given transform function to each element and its index in the original collection and appends the results to the given destination.

Since Kotlin 1.0

inline fun <T, R : Any> Iterable<T>.mapNotNull(transform: (T) -> R?): List<R>

Returns a list containing only the non-null results of applying the given transform function to each element in the original collection.

Since Kotlin 1.0

inline fun <T, R : Any, C : MutableCollection<in R>> Iterable<T>.mapNotNullTo(destination: C, transform: (T) -> R?): C

Applies the given transform function to each element in the original collection and appends only the non-null results to the given destination.

Since Kotlin 1.0

inline fun <T, R, C : MutableCollection<in R>> Iterable<T>.mapTo(destination: C, transform: (T) -> R): C

Applies the given transform function to each element of the original collection and appends the results to the given destination.

Since Kotlin 1.0

@JvmName(name = "maxOrThrow")

fun <T : Comparable<T>> Iterable<T>.max(): T

@JvmName(name = "maxOrThrow")

fun Iterable<Double>.max(): Double

@JvmName(name = "maxOrThrow")

fun Iterable<Float>.max(): Float

Returns the largest element.

Since Kotlin 1.7

fun <T : Comparable<T>> Iterable<T>.~~max~~(): T?

Since Kotlin 1.0

fun Iterable<Double>.~~max~~(): Double?

fun Iterable<Float>.~~max~~(): Float?

Since Kotlin 1.1

@JvmName(name = "maxByOrThrow")

inline fun <T, R : Comparable<R>> Iterable<T>.maxBy(selector: (T) -> R): T

Returns the first element yielding the largest value of the given function.

Since Kotlin 1.7

inline fun <T, R : Comparable<R>> Iterable<T>.~~maxBy~~(selector: (T) -> R): T?

Since Kotlin 1.0

inline fun <T, R : Comparable<R>> Iterable<T>.maxByOrNull(selector: (T) -> R): T?

Returns the first element yielding the largest value of the given function or null if there are no elements.

Since Kotlin 1.4

inline fun <T, R : Comparable<R>> Iterable<T>.maxOf(selector: (T) -> R): R

inline fun <T> Iterable<T>.maxOf(selector: (T) -> Double): Double

inline fun <T> Iterable<T>.maxOf(selector: (T) -> Float): Float

Returns the largest value among all values produced by selector function applied to each element in the collection.

Since Kotlin 1.4

inline fun <T, R : Comparable<R>> Iterable<T>.maxOfOrNull(selector: (T) -> R): R?

inline fun <T> Iterable<T>.maxOfOrNull(selector: (T) -> Double): Double?

inline fun <T> Iterable<T>.maxOfOrNull(selector: (T) -> Float): Float?

Returns the largest value among all values produced by selector function applied to each element in the collection or null if there are no elements.

Since Kotlin 1.4

inline fun <T, R> Iterable<T>.maxOfWith(comparator: Comparator<in R>, selector: (T) -> R): R

Returns the largest value according to the provided comparator among all values produced by selector function applied to each element in the collection.

Since Kotlin 1.4

maxOfWithOrNull

inline fun <T, R> Iterable<T>.maxOfWithOrNull(comparator: Comparator<in R>, selector: (T) -> R): R?

Returns the largest value according to the provided comparator among all values produced by selector function applied to each element in the collection or null if there are no elements.

Since Kotlin 1.4

fun <T : Comparable<T>> Iterable<T>.maxOrNull(): T?

fun Iterable<Double>.maxOrNull(): Double?

fun Iterable<Float>.maxOrNull(): Float?

Returns the largest element or null if there are no elements.

Since Kotlin 1.4

@JvmName(name = "maxWithOrThrow")

fun <T> Iterable<T>.maxWith(comparator: Comparator<in T>): T

Returns the first element having the largest value according to the provided comparator.

Since Kotlin 1.7

fun <T> Iterable<T>.~~maxWith~~(comparator: Comparator<in T>): T?

Since Kotlin 1.0

fun <T> Iterable<T>.maxWithOrNull(comparator: Comparator<in T>): T?

Returns the first element having the largest value according to the provided comparator or null if there are no elements.

Since Kotlin 1.4

@JvmName(name = "minOrThrow")

fun <T : Comparable<T>> Iterable<T>.min(): T

@JvmName(name = "minOrThrow")

fun Iterable<Double>.min(): Double

@JvmName(name = "minOrThrow")

fun Iterable<Float>.min(): Float

Returns the smallest element.

Since Kotlin 1.7

fun <T : Comparable<T>> Iterable<T>.~~min~~(): T?

Since Kotlin 1.0

fun Iterable<Double>.~~min~~(): Double?

fun Iterable<Float>.~~min~~(): Float?

Since Kotlin 1.1

@JvmName(name = "minByOrThrow")

inline fun <T, R : Comparable<R>> Iterable<T>.minBy(selector: (T) -> R): T

Returns the first element yielding the smallest value of the given function.

Since Kotlin 1.7

inline fun <T, R : Comparable<R>> Iterable<T>.~~minBy~~(selector: (T) -> R): T?

Since Kotlin 1.0

inline fun <T, R : Comparable<R>> Iterable<T>.minByOrNull(selector: (T) -> R): T?

Returns the first element yielding the smallest value of the given function or null if there are no elements.

Since Kotlin 1.4

inline fun <T, R : Comparable<R>> Iterable<T>.minOf(selector: (T) -> R): R

inline fun <T> Iterable<T>.minOf(selector: (T) -> Double): Double

inline fun <T> Iterable<T>.minOf(selector: (T) -> Float): Float

Returns the smallest value among all values produced by selector function applied to each element in the collection.

Since Kotlin 1.4

inline fun <T, R : Comparable<R>> Iterable<T>.minOfOrNull(selector: (T) -> R): R?

inline fun <T> Iterable<T>.minOfOrNull(selector: (T) -> Double): Double?

inline fun <T> Iterable<T>.minOfOrNull(selector: (T) -> Float): Float?

Returns the smallest value among all values produced by selector function applied to each element in the collection or null if there are no elements.

Since Kotlin 1.4

inline fun <T, R> Iterable<T>.minOfWith(comparator: Comparator<in R>, selector: (T) -> R): R

Returns the smallest value according to the provided comparator among all values produced by selector function applied to each element in the collection.

Since Kotlin 1.4

minOfWithOrNull

inline fun <T, R> Iterable<T>.minOfWithOrNull(comparator: Comparator<in R>, selector: (T) -> R): R?

Returns the smallest value according to the provided comparator among all values produced by selector function applied to each element in the collection or null if there are no elements.

Since Kotlin 1.4

fun <T : Comparable<T>> Iterable<T>.minOrNull(): T?

fun Iterable<Double>.minOrNull(): Double?

fun Iterable<Float>.minOrNull(): Float?

Returns the smallest element or null if there are no elements.

Since Kotlin 1.4

operator fun <T> Iterable<T>.minus(element: T): List<T>

Returns a list containing all elements of the original collection without the first occurrence of the given element.

Since Kotlin 1.0

operator fun <T> Iterable<T>.minus(elements: Array<out T>): List<T>

Returns a list containing all elements of the original collection except the elements contained in the given elements array.

Since Kotlin 1.0

operator fun <T> Iterable<T>.minus(elements: Iterable<T>): List<T>

Returns a list containing all elements of the original collection except the elements contained in the given elements collection.

Since Kotlin 1.0

operator fun <T> Iterable<T>.minus(elements: Sequence<T>): List<T>

Returns a list containing all elements of the original collection except the elements contained in the given elements sequence.

Since Kotlin 1.0

inline fun <T> Iterable<T>.minusElement(element: T): List<T>

Returns a list containing all elements of the original collection without the first occurrence of the given element.

Since Kotlin 1.0

@JvmName(name = "minWithOrThrow")

fun <T> Iterable<T>.minWith(comparator: Comparator<in T>): T

Returns the first element having the smallest value according to the provided comparator.

Since Kotlin 1.7

fun <T> Iterable<T>.~~minWith~~(comparator: Comparator<in T>): T?

Since Kotlin 1.0

fun <T> Iterable<T>.minWithOrNull(comparator: Comparator<in T>): T?

Returns the first element having the smallest value according to the provided comparator or null if there are no elements.

Since Kotlin 1.4

fun <T> Iterable<T>.none(): Boolean

Returns true if the collection has no elements.

Since Kotlin 1.0

inline fun <T> Iterable<T>.none(predicate: (T) -> Boolean): Boolean

Returns true if no elements match the given predicate.

Since Kotlin 1.0

inline fun <T> Collection<T>?.orEmpty(): Collection<T>

Returns this Collection if it's not null and the empty list otherwise.

Since Kotlin 1.0

inline fun <T> Iterable<T>.partition(predicate: (T) -> Boolean): Pair<List<T>, List<T>>

Splits the original collection into pair of lists, where first list contains elements for which predicate yielded true, while second list contains elements for which predicate yielded false.

Since Kotlin 1.0

operator fun <T> Collection<T>.plus(element: T): List<T>

operator fun <T> Iterable<T>.plus(element: T): List<T>

Returns a list containing all elements of the original collection and then the given element.

Since Kotlin 1.0

operator fun <T> Collection<T>.plus(elements: Array<out T>): List<T>

operator fun <T> Iterable<T>.plus(elements: Array<out T>): List<T>

Returns a list containing all elements of the original collection and then all elements of the given elements array.

Since Kotlin 1.0

operator fun <T> Collection<T>.plus(elements: Iterable<T>): List<T>

operator fun <T> Iterable<T>.plus(elements: Iterable<T>): List<T>

Returns a list containing all elements of the original collection and then all elements of the given elements collection.

Since Kotlin 1.0

operator fun <T> Collection<T>.plus(elements: Sequence<T>): List<T>

operator fun <T> Iterable<T>.plus(elements: Sequence<T>): List<T>

Returns a list containing all elements of the original collection and then all elements of the given elements sequence.

Since Kotlin 1.0

inline fun <T> Collection<T>.plusElement(element: T): List<T>

inline fun <T> Iterable<T>.plusElement(element: T): List<T>

Returns a list containing all elements of the original collection and then the given element.

Since Kotlin 1.0

inline fun <T> Collection<T>.random(): T

Returns a random element from this collection.

Since Kotlin 1.3

fun <T> Collection<T>.random(random: Random): T

Returns a random element from this collection using the specified source of randomness.

Since Kotlin 1.3

inline fun <T> Collection<T>.randomOrNull(): T?

Returns a random element from this collection, or null if this collection is empty.

Since Kotlin 1.4

fun <T> Collection<T>.randomOrNull(random: Random): T?

Returns a random element from this collection using the specified source of randomness, or null if this collection is empty.

Since Kotlin 1.4

inline fun <S, T : S> Iterable<T>.reduce(operation: (acc: S, T) -> S): S

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

Since Kotlin 1.0

inline fun <S, T : S> Iterable<T>.reduceIndexed(operation: (index: Int, acc: S, T) -> S): S

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

Since Kotlin 1.0

reduceIndexedOrNull

inline fun <S, T : S> Iterable<T>.reduceIndexedOrNull(operation: (index: Int, acc: S, T) -> S): S?

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

Since Kotlin 1.4

inline fun <S, T : S> Iterable<T>.reduceOrNull(operation: (acc: S, T) -> S): S?

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

Since Kotlin 1.4

fun <T : Any> Iterable<T?>.requireNoNulls(): Iterable<T>

Returns an original collection containing all the non-null elements, throwing an IllegalArgumentException if there are any null elements.

Since Kotlin 1.0

fun <T> Iterable<T>.reversed(): List<T>

Returns a list with elements in reversed order.

Since Kotlin 1.0

inline fun <T, R> Iterable<T>.runningFold(initial: R, operation: (acc: R, T) -> R): List<R>

Returns a list containing successive accumulation values generated by applying operation from left to right to each element and current accumulator value that starts with initial value.

Since Kotlin 1.4

runningFoldIndexed

inline fun <T, R> Iterable<T>.runningFoldIndexed(initial: R, operation: (index: Int, acc: R, T) -> R): List<R>

Returns a list containing successive accumulation values generated by applying operation from left to right to each element, its index in the original collection and current accumulator value that starts with initial value.

Since Kotlin 1.4

inline fun <S, T : S> Iterable<T>.runningReduce(operation: (acc: S, T) -> S): List<S>

Returns a list containing successive accumulation values generated by applying operation from left to right to each element and current accumulator value that starts with the first element of this collection.

Since Kotlin 1.4

runningReduceIndexed

inline fun <S, T : S> Iterable<T>.runningReduceIndexed(operation: (index: Int, acc: S, T) -> S): List<S>

Returns a list containing successive accumulation values generated by applying operation from left to right to each element, its index in the original collection and current accumulator value that starts with the first element of this collection.

Since Kotlin 1.4

inline fun <T, R> Iterable<T>.scan(initial: R, operation: (acc: R, T) -> R): List<R>

Returns a list containing successive accumulation values generated by applying operation from left to right to each element and current accumulator value that starts with initial value.

Since Kotlin 1.4

inline fun <T, R> Iterable<T>.scanIndexed(initial: R, operation: (index: Int, acc: R, T) -> R): List<R>

Returns a list containing successive accumulation values generated by applying operation from left to right to each element, its index in the original collection and current accumulator value that starts with initial value.

Since Kotlin 1.4

expect fun <T> Iterable<T>.shuffled(): List<T>

Returns a new list with the elements of this collection randomly shuffled.

Since Kotlin 1.2

fun <T> Iterable<T>.shuffled(random: Random): List<T>

Returns a new list with the elements of this list randomly shuffled using the specified random instance as the source of randomness.

Since Kotlin 1.3

actual fun <T> Iterable<T>.shuffled(): List<T>

Returns a new list with the elements of this collection randomly shuffled.

Since Kotlin 1.2

actual fun <T> Iterable<T>.shuffled(): List<T>

Returns a new list with the elements of this collection randomly shuffled.

Since Kotlin 1.2

fun <T> Iterable<T>.shuffled(random: Random): List<T>

Returns a new list with the elements of this list randomly shuffled using the specified random instance as the source of randomness.

Since Kotlin 1.2

actual fun <T> Iterable<T>.shuffled(): List<T>

Returns a new list with the elements of this collection randomly shuffled.

Since Kotlin 1.3

actual fun <T> Iterable<T>.shuffled(): List<T>

Returns a new list with the elements of this collection randomly shuffled.

Since Kotlin 1.8

actual fun <T> Iterable<T>.shuffled(): List<T>

Returns a new list with the elements of this collection randomly shuffled.

Since Kotlin 1.8

fun <T> Iterable<T>.single(): T

Returns the single element, or throws an exception if the collection is empty or has more than one element.

Since Kotlin 1.0

inline fun <T> Iterable<T>.single(predicate: (T) -> Boolean): T

Returns the single element matching the given predicate, or throws exception if there is no or more than one matching element.

Since Kotlin 1.0

fun <T> Iterable<T>.singleOrNull(): T?

Returns single element, or null if the collection is empty or has more than one element.

Since Kotlin 1.0

inline fun <T> Iterable<T>.singleOrNull(predicate: (T) -> Boolean): T?

Returns the single element matching the given predicate, or null if element was not found or more than one element was found.

Since Kotlin 1.0

fun <T : Comparable<T>> Iterable<T>.sorted(): List<T>

Returns a list of all elements sorted according to their natural sort order.

Since Kotlin 1.0

inline fun <T, R : Comparable<R>> Iterable<T>.sortedBy(crossinline selector: (T) -> R?): List<T>

Returns a list of all elements sorted according to natural sort order of the value returned by specified selector function.

Since Kotlin 1.0

sortedByDescending

inline fun <T, R : Comparable<R>> Iterable<T>.sortedByDescending(crossinline selector: (T) -> R?): List<T>

Returns a list of all elements sorted descending according to natural sort order of the value returned by specified selector function.

Since Kotlin 1.0

sortedDescending

fun <T : Comparable<T>> Iterable<T>.sortedDescending(): List<T>

Returns a list of all elements sorted descending according to their natural sort order.

Since Kotlin 1.0

fun <T> Iterable<T>.sortedWith(comparator: Comparator<in T>): List<T>

Returns a list of all elements sorted according to the specified comparator.

Since Kotlin 1.0

infix fun <T> Iterable<T>.subtract(other: Iterable<T>): Set<T>

Returns a set containing all elements that are contained by this collection and not contained by the specified collection.

Since Kotlin 1.0

@JvmName(name = "sumOfByte")

fun Iterable<Byte>.sum(): Int

@JvmName(name = "sumOfDouble")

fun Iterable<Double>.sum(): Double

@JvmName(name = "sumOfFloat")

fun Iterable<Float>.sum(): Float

@JvmName(name = "sumOfInt")

fun Iterable<Int>.sum(): Int

@JvmName(name = "sumOfLong")

fun Iterable<Long>.sum(): Long

@JvmName(name = "sumOfShort")

fun Iterable<Short>.sum(): Int

Returns the sum of all elements in the collection.

Since Kotlin 1.0

@JvmName(name = "sumOfUByte")

fun Iterable<UByte>.sum(): UInt

@JvmName(name = "sumOfUInt")

fun Iterable<UInt>.sum(): UInt

@JvmName(name = "sumOfULong")

fun Iterable<ULong>.sum(): ULong

@JvmName(name = "sumOfUShort")

fun Iterable<UShort>.sum(): UInt

Returns the sum of all elements in the collection.

Since Kotlin 1.5

inline fun <T> Iterable<T>.~~sumBy~~(selector: (T) -> Int): Int

Returns the sum of all values produced by selector function applied to each element in the collection.

Since Kotlin 1.0

inline fun <T> Iterable<T>.~~sumByDouble~~(selector: (T) -> Double): Double

Returns the sum of all values produced by selector function applied to each element in the collection.

Since Kotlin 1.0

@JvmName(name = "sumOfDouble")

inline fun <T> Iterable<T>.sumOf(selector: (T) -> Double): Double

@JvmName(name = "sumOfInt")

inline fun <T> Iterable<T>.sumOf(selector: (T) -> Int): Int

@JvmName(name = "sumOfLong")

inline fun <T> Iterable<T>.sumOf(selector: (T) -> Long): Long

Returns the sum of all values produced by selector function applied to each element in the collection.

Since Kotlin 1.4

@JvmName(name = "sumOfUInt")

inline fun <T> Iterable<T>.sumOf(selector: (T) -> UInt): UInt

@JvmName(name = "sumOfULong")

inline fun <T> Iterable<T>.sumOf(selector: (T) -> ULong): ULong

Returns the sum of all values produced by selector function applied to each element in the collection.

Since Kotlin 1.5

@JvmName(name = "sumOfBigDecimal")

inline fun <T> Iterable<T>.sumOf(selector: (T) -> BigDecimal): BigDecimal

@JvmName(name = "sumOfBigInteger")

inline fun <T> Iterable<T>.sumOf(selector: (T) -> BigInteger): BigInteger

Returns the sum of all values produced by selector function applied to each element in the collection.

Since Kotlin 1.4

fun <T> Iterable<T>.take(n: Int): List<T>

Returns a list containing first n elements.

Since Kotlin 1.0

inline fun <T> Iterable<T>.takeWhile(predicate: (T) -> Boolean): List<T>

Returns a list containing first elements satisfying the given predicate.

Since Kotlin 1.0

fun Collection<Boolean>.toBooleanArray(): BooleanArray

Returns an array of Boolean containing all of the elements of this collection.

Since Kotlin 1.0

fun Collection<Byte>.toByteArray(): ByteArray

Returns an array of Byte containing all of the elements of this collection.

Since Kotlin 1.0

fun Collection<Char>.toCharArray(): CharArray

Returns an array of Char containing all of the elements of this collection.

Since Kotlin 1.0

fun <T, C : MutableCollection<in T>> Iterable<T>.toCollection(destination: C): C

Appends all elements to the given destination collection.

Since Kotlin 1.0

fun Collection<Double>.toDoubleArray(): DoubleArray

Returns an array of Double containing all of the elements of this collection.

Since Kotlin 1.0

fun Collection<Float>.toFloatArray(): FloatArray

Returns an array of Float containing all of the elements of this collection.

Since Kotlin 1.0

fun <T> Iterable<T>.toHashSet(): HashSet<T>

Returns a new HashSet of all elements.

Since Kotlin 1.0

fun Collection<Int>.toIntArray(): IntArray

Returns an array of Int containing all of the elements of this collection.

Since Kotlin 1.0

fun <T> Iterable<T>.toList(): List<T>

Returns a List containing all elements.

Since Kotlin 1.0

fun Collection<Long>.toLongArray(): LongArray

Returns an array of Long containing all of the elements of this collection.

Since Kotlin 1.0

fun <K, V> Iterable<Pair<K, V>>.toMap(): Map<K, V>

Returns a new map containing all key-value pairs from the given collection of pairs.

Since Kotlin 1.0

fun <K, V, M : MutableMap<in K, in V>> Iterable<Pair<K, V>>.toMap(destination: M): M

Populates and returns the destination mutable map with key-value pairs from the given collection of pairs.

Since Kotlin 1.0

fun <T> Collection<T>.toMutableList(): MutableList<T>

fun <T> Iterable<T>.toMutableList(): MutableList<T>

Returns a new MutableList filled with all elements of this collection.

Since Kotlin 1.0

fun <T> Iterable<T>.toMutableSet(): MutableSet<T>

Returns a new MutableSet containing all distinct elements from the given collection.

Since Kotlin 1.0

fun <T> Iterable<T>.toSet(): Set<T>

Returns a Set of all elements.

Since Kotlin 1.0

fun Collection<Short>.toShortArray(): ShortArray

Returns an array of Short containing all of the elements of this collection.

Since Kotlin 1.0

fun <T : Comparable<T>> Iterable<T>.toSortedSet(): SortedSet<T>

fun <T> Iterable<T>.toSortedSet(comparator: Comparator<in T>): SortedSet<T>

Returns a new SortedSet of all elements.

Since Kotlin 1.0

expect inline fun <T> Collection<T>.toTypedArray(): Array<T>

Returns a typed array containing all the elements of this collection.

Since Kotlin 1.0

actual inline fun <T> Collection<T>.toTypedArray(): Array<T>

Returns a typed array containing all the elements of this collection.

Since Kotlin 1.1

actual inline fun <T> Collection<T>.toTypedArray(): Array<T>

Returns a typed array containing all the elements of this collection.

Since Kotlin 1.0

actual inline fun <T> Collection<T>.toTypedArray(): Array<T>

Returns a typed array containing all the elements of this collection.

Since Kotlin 1.3

actual inline fun <T> Collection<T>.toTypedArray(): Array<T>

Returns a typed array containing all the elements of this collection.

Since Kotlin 1.8

actual inline fun <T> Collection<T>.toTypedArray(): Array<T>

Returns a typed array containing all the elements of this collection.

Since Kotlin 1.8

@ExperimentalUnsignedTypes

fun Collection<UByte>.toUByteArray(): UByteArray

Returns an array of UByte containing all of the elements of this collection.

Since Kotlin 1.3

@ExperimentalUnsignedTypes

fun Collection<UInt>.toUIntArray(): UIntArray

Returns an array of UInt containing all of the elements of this collection.

Since Kotlin 1.3

@ExperimentalUnsignedTypes

fun Collection<ULong>.toULongArray(): ULongArray

Returns an array of ULong containing all of the elements of this collection.

Since Kotlin 1.3

@ExperimentalUnsignedTypes

fun Collection<UShort>.toUShortArray(): UShortArray

Returns an array of UShort containing all of the elements of this collection.

Since Kotlin 1.3

infix fun <T> Iterable<T>.union(other: Iterable<T>): Set<T>

Returns a set containing all distinct elements from both collections.

Since Kotlin 1.0

fun <T, R> Iterable<Pair<T, R>>.unzip(): Pair<List<T>, List<R>>

Returns a pair of lists, where first list is built from the first values of each pair from this collection, second list is built from the second values of each pair from this collection.

Since Kotlin 1.0

waitForMultipleFutures

fun <T> Collection<Future<T>>.~~waitForMultipleFutures~~(millis: Int): Set<Future<T>>

Since Kotlin 1.3

fun <T> Iterable<T>.windowed(size: Int, step: Int = 1, partialWindows: Boolean = false): List<List<T>>

Returns a list of snapshots of the window of the given size sliding along this collection with the given step, where each snapshot is a list.

Since Kotlin 1.2

fun <T, R> Iterable<T>.windowed(size: Int, step: Int = 1, partialWindows: Boolean = false, transform: (List<T>) -> R): List<R>

Returns a list of results of applying the given transform function to an each list representing a view over the window of the given size sliding along this collection with the given step.

Since Kotlin 1.2

fun <T> Iterable<T>.withIndex(): Iterable<IndexedValue<T>>

Returns a lazy Iterable that wraps each element of the original collection into an IndexedValue containing the index of that element and the element itself.

Since Kotlin 1.0

infix fun <T, R> Iterable<T>.zip(other: Array<out R>): List<Pair<T, R>>

Returns a list of pairs built from the elements of this collection and the other array with the same index. The returned list has length of the shortest collection.

Since Kotlin 1.0

infix fun <T, R> Iterable<T>.zip(other: Iterable<R>): List<Pair<T, R>>

Returns a list of pairs built from the elements of this collection and other collection with the same index. The returned list has length of the shortest collection.

Since Kotlin 1.0

inline fun <T, R, V> Iterable<T>.zip(other: Array<out R>, transform: (a: T, b: R) -> V): List<V>

Returns a list of values built from the elements of this collection and the other array with the same index using the provided transform function applied to each pair of elements. The returned list has length of the shortest collection.

Since Kotlin 1.0

inline fun <T, R, V> Iterable<T>.zip(other: Iterable<R>, transform: (a: T, b: R) -> V): List<V>

Returns a list of values built from the elements of this collection and the other collection with the same index using the provided transform function applied to each pair of elements. The returned list has length of the shortest collection.

Since Kotlin 1.0

fun <T> Iterable<T>.zipWithNext(): List<Pair<T, T>>

Returns a list of pairs of each two adjacent elements in this collection.

Since Kotlin 1.2

inline fun <T, R> Iterable<T>.zipWithNext(transform: (a: T, b: T) -> R): List<R>

Returns a list containing the results of applying the given transform function to an each pair of two adjacent elements in this collection.

Since Kotlin 1.2

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