Loops in Kotlin: While- and For-Loop

Back to course overview

Hi and welcome to the next tutorial that will cover one of the programming basics. In this session we will learn about Loops, to be more specific about while and for-loops in Kotlin.

Loops allow us to repeat certain parts of our Code. This helps to reduce the amount of code we need to write. It also allows us to repeat certain code lines until it we are satisfied with the output.

For example: We can use loops to validate User Input. We then continue as soon as the user has entered a valid input.

Here is the video to follow along:

Video

References:

URLs:

Kotlin Documentation about Loops

Code:

import kotlin.random.Random

fun main() {
    //while loops
    while (true) {
        println("Test")
        Thread.sleep(1000)
        break
    }

    var counter = 0
    while (counter < 5){
        println("Counter: $counter")
        counter += 1
    }

    do {
        val myValue = Random.nextBoolean()
        println("MyValue is $myValue")
    } while (myValue)

    //for loops
    for (count in 1..5){
        println(count)
    }

    for (i in 10 downTo 0 step 2){
        println(i)
    }
    //loops over collection

    val myList = listOf("Marcus", "Eisele", "Tutorials", "Kotlin")
    for (str in myList){
        println(str)
    }

    for (i in myList.indices){
        println("$i ${myList[i]}")
    }

    for ((index, value) in myList.withIndex().reversed()){
        println("$index $value")
    }


    //create a loop to validate our user input
    var validatedNumber: Int? = null
    while (validatedNumber == null){
        println("Please give us a valid number:")
        validatedNumber = readLine()?.toIntOrNull()
    }

    println("The user entered: $validatedNumber")

    when(validatedNumber){
        3 -> println("Hey I can't stand the number 3!")
        7 -> println("Hey 7 is my lucky number!")
        else -> println("Ah $validatedNumber is pretty boring")
    }
}

If you have any further questions, leave a comment either here on the Blog, on the Youtube-Video or join the Discord Community.

Marcus Eisele

Loops in Kotlin: While- and For-Loop

Video

References:

URLs:

Code: