In this tutorial, we will learn about when operator in Kotlin. When operator is work same as Switch statement of Java. In Kotlin when operator uses to match an argument with all the branches until it finds a satisfying condition in a branch. After finding satisfying condition it runs all statements inside the scope of that branch. Follow the given example to understand when operator.

Example Program:

fun main(args: Array<String>) {
   val num:Int = 2
   when (num) {
      1 -> print("num is = 1")
      2 -> print("num is = 2")
      else -> {
         print("Out of range")
      }
   }
}

Output:

num is = 2

We when operator we can combine multiple branches using comma. check the following example.

Example Program:

fun main(args: Array<String>) {
   val num:Int = 8
   when (num) {
      1,2,3,4,5 -> print("num is in first range")
      6,7,8,9,10 -> print("num is in second range")
      else -> {
         print("Out of range")
      }
   }
}

Output:

num is in second range

We can also use in or !in to check value in particular range or not.

Example Program:

fun main(args: Array<String>) {
   val num:Int = 12
   when (num) {
      in 1..10 -> print("num is in first range")
      in 10..20 -> print("num is in second range")
      else -> {
         print("Out of range")
      }
   }
}

Output:

num is in second range