Variable Argument Lists

Do you know what vararg keyword is? Using this vararg, you can define a function that takes any number of argument.

The keyword vararg produces a flexibly-sized argument list.

It allows you to pass any number (including zero) of arguments, but it has to be the same type because you can later access it using the parameter name as an Array.

fun max(vararg nums: Int): Int {
  var max = 0
  for (n in nums) {
    if (n > max) max = n
  }
  return max
}

sum(9) // 9
sum(3, 20, 15) // 20

Although Array and List look similar, they are implemented differently – List is a regular library class while Array has the special low level support. Array is actually come from Kotlin’s requirement of compatibility with other programming languages such as Java.

In general, we use List when we need a simple sequence. We only consider an Array if the third party library requires Array type or when we are working with vararg.