toIntOrNull

Parses the string to an Int number or returns null if the string is not a valid representation of an Int.

fun String.toIntOrNull(): Int?(source)

fun main() {
    val validInput = "42"
    val invalidInput = "hello"

    val number1: Int? = validInput.toIntOrNull()
    val number2: Int? = invalidInput.toIntOrNull()

    println("validInput -> $number1")   // prints: validInput -> 42
    println("invalidInput -> $number2") // prints: invalidInput -> null
}

Source