Kotlin Path — 8 courses · 532 lessons

The Kotlin learning path

A guided route from beginner to advanced across every Kotlin course: begin with the language tour, go deep with the Deep Dive, sharpen your craft with Patterns & Refactoring, and finish with reactive systems. Follow the recommended order — or jump to what you need.

Foundations

104 lessons

Kotlin — Language Tour

Start here. The syntax and everyday idioms — values, functions, classes, null-safety, collections, lambdas — enough to read and write real Kotlin.

Start

Core mastery

47 lessons

Kotlin — Deep Dive

Go below the syntax: how types, expressions, OOP, generics, coroutines and the type system actually work — with inline visualizations and runnable practice.

Start

Craft — design & quality

52 challenges

Design Patterns in Kotlin

The GoF catalogue + SOLID, retold idiomatically with objects, sealed types and DSLs. Practised as graded Arena challenges.

Practise in Arena

51 challenges

Refactoring Masterclass

Martin Fowler's refactoring catalogue with progressive step hints — turn smelly code into clean Kotlin, one behaviour-preserving move at a time.

Practise in Arena

Advanced — reactive systems

78 lessons

Reactive — Reactor · Coroutines · WebFlux · Flow

The reactive stack as it appears in production: Project Reactor, the coroutine bridge, Spring WebFlux + DI, advanced pipelines, and modern Coroutine Flow — modelled on a real vehicle-import service.

Start

Apply — platform & interop

28 lessons

Kotlin ↔ Java Interop

Mix Kotlin and Java in one codebase: nullability & platform types, @JvmStatic / @JvmOverloads / @JvmName, SAM conversions, and calling each language from the other.

Start

24 lessons

Android with Kotlin

Kotlin on Android — the core ideas and patterns, level by level, with annotated code you can read and mark complete.

Start

Backend — Spring Boot & Gradle

148 lessons

Kotlin + Spring Boot (with Gradle)

Build real backends: the Gradle task graph, Spring IoC/DI & beans, REST controllers & services, data repositories, testing. Every Spring challenge embeds a hand-rolled mini-Spring so your @Service/@RestController code actually wires and runs.

Start

Open Arena Data-structure drills Playground Kotlin game Back to Developer Hub