Kotlin Program to Concatenate Two Arrays

import java.util.Arrays

fun main(args: Array<String>) {
    val array1 = intArrayOf(1, 2, 3)
    val array2 = intArrayOf(4, 5, 6)

    val aLen = array1.size
    val bLen = array2.size
    val result = IntArray(aLen + bLen)

    System.arraycopy(array1, 0, result, 0, aLen)
    System.arraycopy(array2, 0, result, aLen, bLen)

    println(Arrays.toString(result))
}

Output:

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