Resource worth saving: Learn Modern Kotlin.
freeCodeCamp published a full Kotlin course on YouTube. It is free. The watch time is 10 hours. Beau Carnes wrote the announcement.
Here is what the course covers, in order:
Setup and basics. Install IntelliJ IDEA. Learn how the JVM works. Then type inference, primitive types, control flow with when and loops, and Kotlin null safety.
Functions and collections. Default arguments, vararg, lambda functions, arrays, List, Set, Map, binary search, and error handling.
Modern OOP. Primary and secondary constructors, init blocks, data classes, sealed classes, companion objects, singletons, delegation, extension functions.
Generics, in detail. Variance with in and out, upper bounds, the where clause. Then JVM type erasure, and how to work around it with reified type parameters.
Coroutines. Non-blocking async code with launch, async, runBlocking. Structured concurrency, timeouts, cancellations, withContext.
Flows and reactive streams. Cold streams, intermediate and terminal operators like launchIn and asLiveData, exception transparency, retry logic, lifecycle handling.
You start at your first line of code. You end at asynchronous programming and reactive streams.
The course is free and available now on the
freeCodeCamp.org YouTube channel.
Who it is for: developers who target Android, backend services, or cross-platform apps. It also fits anyone who wants one free path from setup to coroutines, without jumping between scattered docs.