kotlin-stdlib / kotlin.comparisons / nullsFirst

nullsFirst

Common

JVM

Native

1.0

fun <T : Any> nullsFirst(
    comparator: Comparator<in T>
): Comparator<T?>

(source)

Extends the given comparator of non-nullable values to a comparator of nullable values considering null value less than any other value. Non-null values are compared with the provided comparator.

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
val list = listOf(4, null, 1, -2, 3)

val nullsFirstList = list.sortedWith(nullsFirst(reverseOrder()))
println(nullsFirstList) // [null, 4, 3, 1, -2]

val nullsLastList = list.sortedWith(nullsLast(reverseOrder()))
println(nullsLastList) // [4, 3, 1, -2, null]
//sampleEnd
}

Common

JVM

Native

1.0

fun <T : Comparable<T>> nullsFirst(): Comparator<T?>
(source)

Provides a comparator of nullable Comparable values considering null value less than any other value. Non-null values are compared according to their natural order.

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
val list = listOf(4, null, -1, 1)

val nullsFirstList = list.sortedWith(nullsFirst())
println(nullsFirstList) // [null, -1, 1, 4]

val nullsLastList = list.sortedWith(nullsLast())
println(nullsLastList) // [-1, 1, 4, null]
//sampleEnd
}