Loops

Kotlin supports the usual duo of loop constructs found in most languages - the while loop and the for loop. The syntax for while loops in Kotlin will be familiar to most developers, as it is exactly the same as most C-style languages:

    while (true) { 
      println("This will print out for a long time!") 
    } 

The Kotlin for loop is used to iterate over any object that defines a function or extension function with the name iterator. All collections provide this function:

    val list = listOf(1, 2, 3, 4) 
    for (k in list) { 
      println(k) 
    } 
 
    val set = setOf(1, 2, 3, 4) 
    for (k in set) { 
      println(k) 
    } 

Note the syntax using the keyword in. The in operator is always used with for loops. In addition to collections, integral ranges are directly supported either inline or defined outside:

    val oneToTen = 1..10 
    for (k in oneToTen) { 
      for (j in 1..5) { 
        println...