decapitalize
actual fun String.decapitalize(): String (source)Returns a copy of this string having its first letter lowercased, or the original string, if it's empty or already starts with a lower case letter.
import kotlin.test.*
import java.util.*
fun main(args: Array<String>) {
//sampleStart
println("abcd".decapitalize()) // abcd
println("Abcd".decapitalize()) // abcd
//sampleEnd
}