How do I sort a list of values in Kotlin?

In Kotlin, you usually sort a list with sorted():

val numbers = listOf(5, 2, 8, 1)

val sortedNumbers = numbers.sorted()

println(sortedNumbers) // [1, 2, 5, 8]

sorted() returns a new sorted list and does not change the original list.

For descending order, use sortedDescending():

val numbers = listOf(5, 2, 8, 1)

val sortedDescending = numbers.sortedDescending()

println(sortedDescending) // [8, 5, 2, 1]

For objects, sort by a property with sortedBy():

data class Person(val name: String, val age: Int)

val people = listOf(
    Person("Alice", 30),
    Person("Bob", 25),
    Person("Charlie", 35)
)

val sortedByAge = people.sortedBy { it.age }

println(sortedByAge)
// [Person(name=Bob, age=25), Person(name=Alice, age=30), Person(name=Charlie, age=35)]

If you have a mutable list and want to sort it in place, use sort():

val numbers = mutableListOf(5, 2, 8, 1)

numbers.sort()

println(numbers) // [1, 2, 5, 8]

Quick summary:

• sorted() — returns a new ascending list
• sortedDescending() — returns a new descending list
• sortedBy { ... } — sorts by a property
• sort() — sorts a mutable list in place