Introduction to Kotlin
Concise, null-safe JVM language — and Android’s favourite.
What Kotlin is, why it matters, and how to navigate this track.
Kotlin is a concise, null-safe language for the JVM — and Google’s preferred language for Android.
What is Kotlin?
Kotlin is a statically-typed language that interoperates seamlessly with Java while cutting the boilerplate.
Its type system tracks nullability, eliminating the billion-dollar null-pointer mistake at compile time.
Your first example
Here is Kotlin saying hello. Read it top to bottom — every line earns its place.
fun main() {
println("Hello, world!")
}Hello, world!
Why learn Kotlin?
- Less ceremony than Java with full Java interop.
- Null safety baked into the type system.
- First-class for Android, and capable on the server and multiplatform.
Where it is used
- Android apps
- JVM backends
- Multiplatform code
- Replacing Java incrementally
How this track works
Every topic here has four views, switchable with the tabs at the top of each page:
- Learn — the clear, practical walkthrough you are reading now.
- Deep — every detail: edge cases, the full API, and what is really happening.
- Reference — a scannable, no-fluff lookup for when you already know the shape.
- Cheatsheet — the one-page summary, printable, for quick recall.
More like this
HTML Headings
h1 through h6 are the page’s table of contents. Use them for structure, never for size — that’s what CSS is for.
HTML Headings
h1–h6 are instances of HTMLHeadingElement. They take no special attributes — only the global set and ARIA — but there’s real depth in how they form the document outline and what you can do with them from JavaScript.
Liked this one?
Pass it on
Discussion
Be the first to ask
Your questions stay private with the team. We can pin answers to share with everyone.
Sign in to ask a question privately on this tutorial.
Sign inNo pinned answers yet for this tutorial.