kotlin-stdlib/kotlin.text/replaceFirstChar

replaceFirstChar

@JvmName(name = "replaceFirstCharWithChar")
inline fun String.replaceFirstChar(transform: (Char) -> Char): String(source)
@JvmName(name = "replaceFirstCharWithCharSequence")
inline fun String.replaceFirstChar(transform: (Char) -> CharSequence): String(source)

Returns a copy of this string having its first character replaced with the result of the specified transform, or the original string if it's empty.

Since Kotlin

1.5

Parameters

transform

function that takes the first character and returns the result of the transform applied to the character.

Samples

import java.util.Locale
import kotlin.test.*

fun main() { 
   //sampleStart 
   println("kotlin".replaceFirstChar { it.uppercase() }) // Kotlin

val sentence = "Welcome to Kotlin!"
val words = sentence.split(' ');
println(words.joinToString(separator = "_") { word -> word.replaceFirstChar { it.lowercase() } }) // welcome_to_kotlin! 
   //sampleEnd
}