padStart
Returns a char sequence with content of this char sequence padded at the beginning to the specified length with the specified character or space.
fun CharSequence.padStart(length: Int, padChar: Char = ' '): CharSequence(source)
fun main() {
val paddedWithZeroes = "42".padStart(5, '0')
val paddedWithSpaces = "42".padStart(5)
println(paddedWithZeroes) // 00042
println(paddedWithSpaces) // 42
}