While Loop in Kotlin

In this tutorial, we will learn about while loop in Kotlin. We will cover the basics of iterative execution using while loops.

What is a While Loop

A while loop is a control flow statement that allows code to be executed repeatedly based on a given Boolean condition. The loop runs as long as the condition evaluates to true.

Syntax

The syntax for the while loop in Kotlin is:

while (condition) {
    // Code block to be executed
}

The while loop evaluates the condition before executing the loop's body. If the condition is true, the code block inside the loop is executed. This process repeats until the condition becomes false.


Example 1: Printing Numbers from 1 to 5

  1. Declare a variable i and initialize it to 1.
  2. Use a while loop to print numbers from 1 to 5.

Kotlin Program

fun main() {
    var i = 1
    while (i <= 5) {
        println(i)
        i++
    }
}

Output

1
2
3
4
5

Example 2: Calculating the Sum of First N Natural Numbers

  1. Declare variables n and sum.
  2. Assign a value to n.
  3. Initialize sum to 0.
  4. Use a while loop to calculate the sum of the first n natural numbers.
  5. Print the sum.

Kotlin Program

fun main() {
    val n = 10
    var sum = 0
    var i = 1
    while (i <= n) {
        sum += i
        i++
    }
    println("Sum of first $n natural numbers is $sum")
}

Output

Sum of first 10 natural numbers is 55

Example 3: Reversing a Number

  1. Declare variables num and rev.
  2. Assign a value to num.
  3. Initialize rev to 0.
  4. Use a while loop to reverse the digits of num.
  5. Print the reversed number.

Kotlin Program

fun main() {
    var num = 12345
    var rev = 0
    while (num != 0) {
        val digit = num % 10
        rev = rev * 10 + digit
        num /= 10
    }
    println("Reversed number is $rev")
}

Output

Reversed number is 54321