Search⌘ K
AI Features
Home
Courses
Kotlin Crash Course for Programmers

`for` Loops

Explore Kotlin for loops and how they work with iterables like ranges, collections, and strings. Understand when to use for loops versus while loops and practice nesting loops with exercises to solidify your grasp on flexible iteration strategies.

We'll cover the following...

In contrast to while loops, Kotlin’s for loops work a bit differently than you may be used to from other languages.

for Loops #

Kotlin’s for loops are different from many other languages because they’re used in the same manner as for-each loops (or for-in loops). Thus, you always give an iterable to the for loop over which it iterates:

Kotlin
for (number in 1..5) println(number)        // 1, 2, 3, 4, 5
for (number in 1 until 5) println(number)   // 1, 2, 3, 4
for (number in 1..5 step 2) println(number) // 1, 3, 5
for (number in 5 downTo 1) println(number)  // 5, 4, 3, 2, 1
for (number in 5 downTo 1 step 2) println(number)  // 5, 3, 1
for (char in 'a'..'c') println(char)        // 'a', 'b', 'c'
for (planet in planets) println(planet)     // "Jupiter", "Saturn", ...
for (char in "Venus") println(char)         // 'V', 'e', 'n', 'u', 's'

A few things to note here:

  • Ranges are commonly used for basic loops, e.g., 1..5.
    • There are utilities to construct more complex ranges,
...