import kotlin.system.measureNanoTime

/**
 * You can edit, run, and share this code.
 * play.kotlinlang.org
 */
val list = (1..100000).toList()

fun main() {
    startMap()
    startFor()
    startForUntil()
    startForIn()
    startForEach()
    startForEachIndexed()
    startWhile()
}

fun startMap() {
   println("Map Time: " + measureNanoTime {
        list.map { i ->
            i
        }
    })
}

fun startFor() {
   println("For Time: " + measureNanoTime {
        for (i in 0..(list.size-1)) { list[i] }
    })
}

fun startForUntil() {
   println("ForUntil Time: " + measureNanoTime {
        for (i in 0 until list.size) { list[i] }
    })
}

fun startForIn() {
   println("ForIn Time: " + measureNanoTime {
        for (i in list.indices) { list[i] }
    })
}

fun startForEach() {
   println("forEach Time: " + measureNanoTime {
        list.forEach { i -> i }
    })
}

fun startForEachIndexed() {
   println("forEachIndexed Time: " + measureNanoTime {
        list.forEachIndexed { index, i -> i }
    })
}

fun startWhile() {
    var i = 0
   println("while Time: " + measureNanoTime {
        while(i<list.size) {
            i++
        }
    })
}

⭐️ 결과

Map Time: 15900184 For Time: 348984 ForUntil Time: 3145461 ForIn Time: 3620592 forEach Time: 6414756 forEachIndexed Time: 7196908 while Time: 7073345

💙 결과적으로 for문이 가장 빨라 많은 데이터를 처리해야할때는 for문을 사용하자!