Loops

Jun 23, 2026Trushi Jasani

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Loops

for Loop

The for loop is used to iterate over ranges, arrays, or collections.

Iterating over a Range

fun main() {
    for (i in 1..5) {
        println(i)
    }
    // Output: 1 2 3 4 5
}

Descending Range with downTo

fun main() {
    for (i in 5 downTo 1) {
        println(i)
    }
    // Output: 5 4 3 2 1
}

Step Increment with step

fun main() {
    for (i in 0..20 step 5) {
        println(i)
    }
    // Output: 0 5 10 15 20
}

Exclusive Range with until

fun main() {
    for (i in 1 until 5) {
        println(i)
    }
    // Output: 1 2 3 4 (excludes 5)
}

Iterating over an Array

fun main() {
    val fruits = arrayOf("Apple", "Banana", "Cherry")

    for (fruit in fruits) {
        println(fruit)
    }
}

Iterating with Index

fun main() {
    val colors = arrayOf("Red", "Green", "Blue")

    for ((index, color) in colors.withIndex()) {
        println("$index: $color")
    }
}

while Loop

Repeats as long as the condition is true.

fun main() {
    var count = 1

    while (count <= 5) {
        println("Count: $count")
        count++
    }
}

do-while Loop

Executes the block at least once, then checks the condition.

fun main() {
    var num = 1

    do {
        println("Number: $num")
        num++
    } while (num <= 5)
}

break — Exit a Loop

fun main() {
    for (i in 1..10) {
        if (i == 6) break
        println(i)
    }
    // Output: 1 2 3 4 5
}

continue — Skip an Iteration

fun main() {
    for (i in 1..10) {
        if (i % 2 == 0) continue
        println(i)
    }
    // Output: 1 3 5 7 9 (odd numbers only)
}

Labeled Loops

Labels help break or continue outer loops:

fun main() {
    outer@ for (i in 1..3) {
        for (j in 1..3) {
            if (j == 2) continue@outer
            println("i=$i, j=$j")
        }
    }
}

Output:

i=1, j=1
i=2, j=1
i=3, j=1

Nested Loops — Multiplication Table

fun main() {
    for (i in 1..5) {
        for (j in 1..5) {
            print("${i * j}\t")
        }
        println()
    }
}

repeat() Function

fun main() {
    repeat(5) { index ->
        println("Iteration $index")
    }
}

Iterating Over a String

fun main() {
    val word = "Kotlin"
    for (char in word) {
        print("$char ")
    }
    // Output: K o t l i n
}

Loop Summary

Loop Type	When to Use
for	Known number of iterations or iterating a collection
while	Repeat while condition is true (check first)
do-while	Execute at least once (check after)
repeat(n)	Run exactly n times with index available
break	Exit loop early
continue	Skip current iteration