Loops

In Kotlin, a loop is a control flow statement that allows repeated execution of a block of code for a certain number of times or until a certain condition is met. Kotlin provides several types of loops, including:

• The for loop, which iterates over a range of values or elements in a collection.
• The while loop, which repeatedly executes a block of code as long as a certain condition is true.
• The do-while loop, which is similar to the while loop, but guarantees that the block of code will be executed at least once before the condition is checked.

The for loop is used to iterate over a range of values or an iterable collection.

Syntax

fun main() {
  for (item in collection) {
    // Code to be executed for each item
  }
}

• The item is an element within the collection.
• The collection is any container for a group of items such as lists and sets.

Example

Below is an example of a for loop that prints the numbers 1 through 10:

fun main() {
  for(i in 1..10){
    print(i.toString() + " ")
  }
}

The .toString() method is used to convert i to a string so that a string operation can be performed on it. This will output:

1 2 3 4 5 6 7 8 9 10

The while loop is used to execute a block of code repeatedly as long as a certain condition is true.

Syntax

fun main() {
  while (condition) {
    // Code to be executed while the condition is true
  }
}

While the condition evaluates to true, the while loop code block will execute.

Example

The example below uses a while loop to print the numbers 1 through 10:

fun main() {
  var i = 1

  while (i <= 10) {
    print(" " + i)
    i++
  }
}

The output for the above code will be:

1 2 3 4 5 6 7 8 9 10

A do-while loop in Kotlin is similar to a while loop, but the code within the do block is executed before the condition is checked.

Syntax

fun main() {
  do {
    // Code to be executed at least once
  } while (condition)
}

Example

In the example below, a variable i is declared with an initial value of 10. The loop will continue to run while i is greater than 0. Upon each iteration of the loop, the value of i is printed and then decremented by 1 until it is no longer greater than 0. Then, the loop will exit and the program will end:

fun main() {
  var i = 10

  do {
    print(" " + i)
    i--
  } while (i > 0)
}

This will output:

10 9 8 7 6 5 4 3 2 1