The when Statement

In this lesson you will learn how to branch on several values with a when statement in Kotlin, which reads more clearly than a chain of if statements. This is for anyone searching for "Kotlin when how to use".

A when statement corresponds to the switch of other languages. No break is needed, and each condition maps to its work with -> - a simple, characteristically Kotlin form.

The sample code prints a different message for 1 -> through 3 -> depending on day, falling back to "Other day" in else ->. Not needing a break at the end of each branch is characteristic of Kotlin.

A common stumbling block for beginners is not realising that when can also be used as an "expression". Used as a when expression it returns a value, so the result of the branch can be assigned straight to a variable.

In real-world development when statements are common wherever you branch on a fixed set of options, such as days of the week or status codes.

📖 Reference code

fun main() {
    val day = 3
    when (day) {
        1 -> println("Monday")
        2 -> println("Tuesday")
        3 -> println("Wednesday")
        else -> println("Other day")
    }
}

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run Kotlin directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).