Conditionals

if produces a value directly in Kotlin, replacing the ternary operator entirely, and when is a far more flexible switch that can test arbitrary conditions.

if as an expression

In Kotlin, if can produce a value directly — there's no separate ternary operator because if/else already does the job:

</> main.kt

fun main() {
    val score = 82
    val grade = if (score >= 90) "A" else if (score >= 80) "B" else "C"

    println(grade)
}

Output

Every branch of the if must produce a value of a compatible type for this to work as an expression — the compiler enforces that else is present, since a missing branch would leave the expression with no value in that case.

when: a more powerful switch

when replaces Java's switch, but it's an expression too, and its branches can be arbitrary conditions, not just exact matches:

</> main.kt

fun main() {
    val hour = 14

    val period = when {
        hour < 12 -> "Morning"
        hour < 17 -> "Afternoon"
        else -> "Evening"
    }

    println(period)
}

Output

Afternoon

Used without an argument like this, each branch is its own boolean condition, checked top to bottom — the first one that's true wins. when can also match against a single value directly, closer to a traditional switch, with when (hour) { 9, 10, 11 -> ...; else -> ... }.

Note: A when expression (one whose result you actually use, like assigning it to a val) must be exhaustive — every possible case has to be covered, usually by ending with an else branch, or the compiler rejects it. A when used only as a statement (its result discarded) doesn't have this requirement.

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