Scala Cookbook

3.5. Implementing break and continue

Problem

You have a situation where you need to use a break or continue construct, but Scala doesn’t have break or continue keywords.

Solution

It’s true that Scala doesn’t have break and continue keywords, but it does offer similar functionality through scala.util.control.Breaks.

The following code demonstrates the Scala “break” and “continue” approach:

package com.alvinalexander.breakandcontinue

import util.control.Breaks._

object BreakAndContinueDemo extends App {

  println("\n=== BREAK EXAMPLE ===")
  breakable {
    for (i <- 1 to 10) {
      println(i)
      if (i > 4) break  // break out of the for loop
    }
  }

  println("\n=== CONTINUE EXAMPLE ===")
  val searchMe = "peter piper picked a peck of pickled peppers"
  var numPs = 0
  for (i <- 0 until searchMe.length) {
    breakable {
      if (searchMe.charAt(i) != 'p') {
        break  // break out of the 'breakable', continue the outside loop
      } else {
        numPs += 1
      }
    }
  }
  println("Found " + numPs + " p's in the string.")
}

Here’s the output from the code:

=== BREAK EXAMPLE ===
1
2
3
4
5

=== CONTINUE EXAMPLE ===
Found 9 p's in the string.

(The “pickled peppers” example comes from a continue example in the Java documentation. More on this at the end of the recipe.)

The following discussions describe how this code works.

The break example

The break example is pretty easy to reason about. Again, here’s the code:

breakable {
  for (i <- 1 to 10) {
    println(i)
    if (i > 4) break  // break out of the for loop
  }
}

In this case, when i becomes greater than 4, the break ...