Compukters Core/kotlin.collections/Collection

Collection

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

A read-only view of a group of elements with size and membership queries.

Read-only access does not guarantee immutability. A view of a mutable collection may observe later changes. Concrete implementations define ordering and whether duplicates are permitted.

Type Parameters

T

element type.

Inheritors

MutableCollection

Properties

abstract val size: Int

Number of elements in this collection.

Functions

abstract fun addAll(p0: Collection<out T?>?): Boolean

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

Returns true when every element matches predicate.

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

Returns true when at least one element matches predicate.

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

Borrows this iterable as a lazy sequence without traversing or copying it. Each traversal requests a new source iterator; later mutations and invalidation follow the iterable's own contract. Wrappers and iterators use ordinary managed heap quotas.

abstract operator fun contains(element: T): Boolean

Checks whether this collection contains an element equal to element.

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

Checks whether this iterable has an element equal to element.

abstract fun containsAll(p0: Collection<*>?): Boolean

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

Returns a list containing elements matching predicate, in their original iteration order.

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

Returns a list of non-null elements in their original iteration order.

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

Appends matching elements to destination in iteration order.

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

Returns the first matching element, or null when no element matches predicate.

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

Returns the first element, throwing NoSuchElementException when empty.

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

Returns the first matching element, throwing NoSuchElementException when no element matches.

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

Returns the first element, or null when this iterable is empty.

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

Returns the first matching element, or null when no element matches predicate.

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

Accumulates elements in iteration order.

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

Calls action for each element in iteration order.

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

Calls action for each element and its zero-based index in iteration order.

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

Returns the index of the first equal element, or -1 when no element matches.

abstract fun isEmpty(): Boolean

Checks whether this collection has no elements.

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

Checks whether this collection contains at least one element.

abstract operator fun iterator(): Iterator<T>

Returns an iterator over this iterable's elements.

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

Returns the index of the last equal element, or -1 when no element matches.

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

Returns the last element, or null when this iterable is empty.

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

Returns the last matching element after traversing this iterable in iteration order.

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

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

Returns a list containing transform applied once to each element in iteration order.

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

Applies transform once per element in iteration order and retains only non-null results.

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

Appends non-null transformed elements to destination in iteration order.

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

Appends transformed elements to destination in iteration order.

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

Returns true when no element matches predicate.

abstract fun removeAll(p0: Collection<*>?): Boolean

abstract fun retainAll(p0: Collection<*>?): Boolean