Learn Modern Kotlin

<p>We just published a comprehensive, free Kotlin course on the freeCodeCamp.org YouTube channel.</p> <p>Whether you're targeting Android development, scalable backend services, or cross-platform applications, this course takes you from writing your first line of code to mastering asynchronous programming and reactive streams.</p> <p>Here are the things covered in this course:</p> <ul> <li><p><strong>Fundamentals &amp; Setup</strong><br>Installing IntelliJ IDEA, understanding the JVM, type inference, primitive types, control flow (<code>when</code>, loops), and Kotlin’s built-in <strong>null safety</strong>.</p> </li> <li><p><strong>Functions &amp; Collections</strong><br>Default arguments, <code>vararg</code>, lambda functions, arrays, collections (<code>List</code>, <code>Set</code>, <code>Map</code>), binary search, and error handling.</p> </li> <li><p><strong>Modern OOP</strong><br>Primary/secondary constructors, <code>init</code> blocks, <code>data</code> classes, <code>sealed</code> classes, companion objects, singletons, delegation, and <strong>extension functions</strong>.</p> </li> <li><p><strong>Deep-Dive Generics</strong><br>Variance (<code>in</code>/<code>out</code>), upper bounds, the <code>where</code> clause, and working around JVM type erasure using <code>reified</code> type parameters.</p> </li> <li><p><strong>Coroutines</strong><br>Non-blocking asynchronous programming using <code>launch</code>, <code>async</code>, <code>runBlocking</code>, structured concurrency, timeouts, cancellations, and <code>withContext</code>.</p> </li> <li><p><strong>Kotlin Flows &amp; Reactive Streams</strong><br>Cold streams, intermediate and terminal operators (<code>launchIn</code>, <code>asLiveData</code>), exception transparency, <code>retry</code> logic, and lifecycle handling.</p> </li> </ul> <p>The course is completely free and available now <a href="https://www.youtube.com/watch?v=nqK3oJ682mQ">on the freeCodeCamp.org YouTube channel</a> (10-hour watch).</p> <div class="embed-wrapper"><iframe width="560" height="315" src="https://www.youtube.com/embed/nqK3oJ682mQ" style="aspect-ratio: 16 / 9; width: 100%; height: auto;" title="YouTube video player" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen="" loading="lazy"></iframe></div>