11. Loops & Labels

Kotlin offers for, while, and do-while loops. Labels let break and continue target an outer loop.

fun main() {
    // for over a range
    for (i in 1..3) print("$i ")
    println()

    // for over a list
    val fruits = listOf("apple", "pear", "plum")
    for (fruit in fruits) print("$fruit ")
    println()

    // for with index and value via withIndex()
    for ((index, fruit) in fruits.withIndex()) {
        println("$index: $fruit")
    }

    // while and do-while
    var n = 3
    while (n > 0) { print("$n "); n-- }
    println()
    do { print("go "); n++ } while (n < 2)
    println()
}

A label like outer@ lets an inner break or continue jump out of the enclosing loop.

fun main() {
    outer@ for (i in 1..3) {
        for (j in 1..3) {
            if (i + j == 4) continue@outer
            if (i == 3) break@outer
            println("i=$i j=$j")
        }
    }
}

Running it:

$ kotlin run
1 2 3 
apple pear plum 
0: apple
1: pear
2: plum
3 2 1 
go go 

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