fun String.capitalize(): String

Returns a copy of this string having its first letter uppercased, or the original string, if it's empty or already starts with an upper case letter.

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
println("abcd".capitalize()) // Abcd
println("Abcd".capitalize()) // Abcd
//sampleEnd
}

@ExperimentalStdlibApi fun String.capitalize(
    locale: Locale
): String

Returns a copy of this string having its first letter titlecased preferring Char.toTitleCase (if different from Char.toUpperCase) or by String.toUpperCase using the specified locale, or the original string, if it's empty or already starts with an upper case letter.