ForEachPerformanceTest.kt

import java.util.UUID
import kotlin.system.measureTimeMillis

fun main() {
    fun newRandomString() = UUID.randomUUID().toString()
    val list = (0..100).map { newRandomString() }.toList()
    val times = 100000
    val a = measureTimeMillis {
        repeat(times) {
            list.forEach { }
        }
    }
    val b = measureTimeMillis {
        repeat(times) {
            list.fastForEach { }
        }
    }
    println("a=$a, b=$b")
}

inline fun <T> List<T>.fastForEach(callback: (T) -> Unit) {
    var n = 0
    while (n < size) callback(this[n++])
}