Idiomatic way to generate a random alphanumeric string in Kotlin

Question

I can generate a random sequence of numbers in a certain range like the following:

fun ClosedRange<Int>.random() = Random().nextInt(endInclusive - start) +  start fun generateRandomNumberList(len: Int, low: Int = 0, high: Int = 255): List<Int> {   (0..len-1).map {     (low..high).random()   }.toList() } 

Then I'll have to extend List with:

fun List<Char>.random() = this[Random().nextInt(this.size)] 

Then I can do:

fun generateRandomString(len: Int = 15): String{   val alphanumerics = CharArray(26) { it -> (it + 97).toChar() }.toSet()       .union(CharArray(9) { it -> (it + 48).toChar() }.toSet())   return (0..len-1).map {       alphanumerics.toList().random()   }.joinToString("") } 

But maybe there's a better way?

Answer 1

Since Kotlin 1.3 you can do this:

fun getRandomString(length: Int) : String {     val allowedChars = ('A'..'Z') + ('a'..'z') + ('0'..'9')     return (1..length)         .map { allowedChars.random() }         .joinToString("") } 

Answer 2

Lazy folks would just do

java.util.UUID.randomUUID().toString() 

You can not restrict the character range here, but I guess it's fine in many situations anyway.