setOf

fun <T> setOf(element: T): Set<T> (source)

Returns an immutable set containing only the specified object element. The returned set is serializable.

fun <T> setOf(vararg elements: T): Set<T> (source)

Returns a new read-only set with the given elements. Elements of the set are iterated in the order they were specified. The returned set is serializable (JVM).

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
val set1 = setOf(1, 2, 3)
val set2 = setOf(3, 2, 1)

// setOf preserves the iteration order of elements
println(set1) // [1, 2, 3]
println(set2) // [3, 2, 1]

// but the sets with the same elements are equal no matter of order
println("set1 == set2 is ${set1 == set2}") // true
//sampleEnd
}
inline fun <T> setOf(): Set<T> (source)

Returns an empty read-only set. The returned set is serializable (JVM).

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
val set = setOf<String>()
println("set.isEmpty() is ${set.isEmpty()}") // true

// another way to create an empty set,
// type parameter is inferred from the expected type
val other: Set<Int> = emptySet()

// Empty sets are equal

println("set == other is ${set == other}") // true
println(set) // []
//sampleEnd
}