how to user if not in kotlin code example

Example 1: Kotlin when

val x = 3
when(x) {
    3 -> println("yes")
    8 -> println("no")
    else -> println("maybe")
}
// when can also be used as an expression!
val y = when(x) {
    3 -> "yes"
    8 -> "no"
    else -> "maybe"
}
println(y) // "yes"

Example 2: kotlin if

if (a > b) {
    max = a
} else {
    max = b
}