while Loops

while repeats as long as a condition is true:

@main def doubling(): Unit =
  var balance = 100.0
  var months = 0
  while balance < 200 do
    balance *= 1.1
    months += 1
  println(s"Doubled after $months months")

Doubled after 8 months

while needs a var that changes — otherwise the loop never ends. That's why idiomatic Scala uses it less than other languages do: collection methods, for, and recursion usually express the same thing without mutable state.

No break or continue

Scala has no break or continue keywords. Instead:

@main def noBreak(): Unit =
  val numbers = List(3, 8, 12, 5, 20)

  val firstBig = numbers.find(_ > 10)
  println(firstBig)

  val beforeBig = numbers.takeWhile(_ <= 10)
  println(beforeBig)

  for n <- numbers if n % 2 == 0 do println(n)

Some(12)
List(3, 8)
8
12
20

• find stops at the first match — the usual reason for break.
• takeWhile takes elements until the condition fails.
• A for filter (if) replaces continue.

(scala.util.boundary exists for the rare case where you really need to exit early from deep inside a loop.)