When should I use while vs for?

Use for when you know the number of iterations or are iterating a collection. Use while when the number of iterations depends on a condition that changes during execution.

What is the difference between while and do-while?

while checks the condition before each iteration. do-while runs the body at least once, then checks the condition.

Beginner 6 min readKotlin 2.0

Kotlin while and do-while Loops

while repeats a block as long as a condition is true. do-while runs the block at least once, then checks the condition.

What You Will Learn

while loop syntax and use
do-while loop
Difference between while and do-while
Infinite loops and how to stop them

while Loop

while checks the condition before each iteration.

while Loop

kotlin
fun main() {
    var count = 1
    while (count <= 5) {
        println(count)
        count++
    }
}

Output

1 2 3 4 5

count starts at 1. Each iteration prints count and increments it. When count becomes 6, the condition is false and the loop ends.

Common Mistake: Forgetting to update the loop variable inside the loop causes an infinite loop. Always ensure the condition will eventually become false.

do-while Loop

do-while executes the block once before checking the condition.

do-while

kotlin
fun main() {
    var n = 0
    do {
        println("n = $n")
        n++
    } while (n < 3)
}

Output

n = 0 n = 1 n = 2

The body runs with n=0, then the condition n < 3 is checked. The loop continues while the condition is true.

break and continue

break exits the loop immediately. continue skips to the next iteration.

break and continue

kotlin
fun main() {
    for (i in 1..10) {
        if (i == 4) continue   // skip 4
        if (i == 7) break      // stop at 7
        print("$i ")
    }
}

Output

1 2 3 5 6

continue skips 4. break stops the loop when i reaches 7. 7 itself is not printed.

Practice Exercise

Exercisepredict output

What prints? var x = 10 while (x > 7) { println(x) x-- }

Quick Quiz

What is the key difference between while and do-while?

Kotlin while and do-while Loops

What You Will Learn

while Loop

while Loop

do-while Loop

do-while

break and continue

break and continue

Practice Exercise

Quick Quiz

Frequently Asked Questions

Related Tutorials