Kotlin doesn't have these exact functions, but they are all special cases of indexOfFirst and indexOfLast:
fun CharSequence.findFirstOf(chars: CharSequence) = indexOfFirst { it in chars }
fun CharSequence.findLastOf(chars: CharSequence) = indexOfLast { it in chars }
fun CharSequence.findFirstNotOf(chars: CharSequence) = indexOfFirst { it !in chars }
fun CharSequence.findLastNotOf(chars: CharSequence) = indexOfLast { it !in chars }
These will return -1 if nothing is found.
Usage:
val s = "abcdefghi"
val chars = "aeiou"
println(s.findFirstOf(chars))
println(s.findFirstNotOf(chars))
println(s.findLastOf(chars))
println(s.findLastNotOf(chars))
Output:
0
1
8
7