While Loop

Sometimes you need to repeat something until a condition changes. That's where while loops come in — keep going while the condition is true.

The `while` loop

A while loop checks the condition first. If it's true, the body runs, then it checks again.


fun main() {
  var count = 3
  while (count > 0) {
    println(count)
    count--
  }
  println("Go!")
}

The -- operator decreases count by 1 each time. Eventually count > 0 becomes false and the loop stops.

You can create an infinite loop with while (true) and use break to exit when ready.


fun main() {
  var number = 1
  while (true) {
    if (number > 5) break
    println(number)
    number++
  }
}

Use break sparingly — it's easy to accidentally create a loop that never ends!

With do...while, the body runs at least once because the condition is checked after.


fun main() {
  var x = 5
  do {
    println(x)
    x++
  } while (x < 3)
}

Even though 5 < 3 is false, the body prints 5 once before the check.

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