Kotlin Lessons
12 hands-on Kotlin lessons, about 216 minutes of material in total, taking you from your first println to null safety, lambdas, and collection pipelines. Every lesson mixes short explanations with exercises you edit and run in the browser — there is nothing to install, and each exercise is checked by real tests rather than a multiple-choice quiz. Work through all of them to earn a free, shareable certificate.
- 01Hello, Kotlin
Print to the console and embed values in strings.
4 steps · about 12 min
- 02val and var
Read-only and mutable bindings — when each one fits.
6 steps · about 18 min
- 03Types
Int, Double, String, Boolean — meet each one with its own example.
8 steps · about 24 min
- 04Logical Operators
&& (and), || (or), and ! (not) — compose booleans into bigger conditions.
8 steps · about 24 min
- 05if and when
Two ways to branch — and how they relate.
6 steps · about 18 min
- 06Loops & Ranges
for over ranges, plus modifiers like step and downTo.
6 steps · about 18 min
- 07Functions
Declarations, defaults, and single-expression form.
6 steps · about 18 min
- 08Classes & Data Classes
Properties, methods, data classes, and mutable state.
6 steps · about 18 min
- 09Collections
Lists, plus the workhorses map and filter.
6 steps · about 18 min
- 10Null Safety
Nullable types, the Elvis operator, and safe calls.
6 steps · about 18 min
- 11Lambdas
Anonymous functions, higher-order functions, and trailing lambdas.
6 steps · about 18 min
- 12Final Challenges
Two classic warm-ups before you wrap up the course.
4 steps · about 12 min
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