Converting a Kotlin List to a Set

Tags:

List.toSet()

You can convert a List to a Set by using the List.toSet() function.

fun main() {
    val list = listOf(1, 2, 3, 4, 5)

    val set = list.toSet()

    println(set)
}

Output:

[1, 2, 3, 4, 5]

MutableList.toMutableSet()

The List.toMutableSet() function returns a Set that can add elements. In the example below, the add() function is used to add an element to set.

fun main() {
    val list = mutableListOf(1, 2, 3, 4, 5)

    val set = list.toMutableSet()
    set.add(6)

    println(set)
}

Output:

[1, 2, 3, 4, 5, 6]

HashSet()

You can also convert to a Set by passing list to the HashSet() constructor function.

fun main() {
    val list = listOf(1, 2, 3, 4, 5)

    val set = HashSet(list)

    println(set)
}

Output:

[1, 2, 3, 4, 5]

Set.addAll()

You can also add the elements of list to a set declared as MutableSet by using the addAll() function.

fun main() {
    val list = listOf(1, 2, 3, 4, 5)

    val set: MutableSet<Int> = HashSet()
    set.addAll(list)

    println(set)
}

Output:

[1, 2, 3, 4, 5]

References