SM - Kotlin Development

Is Kotlin better than Java?

It's less about "better" and more about fit

Choosing between Kotlin and Java isn't about finding the "better" language — it's about picking the one that fits your specific project needs. Both run on the Java Virtual Machine (JVM) and share a rich ecosystem, but they take different approaches to solving the same problems.

Kotlin adds concise syntax, built-in null safety, and first-class coroutines for asynchronous code, while staying fully interoperable with existing Java code and libraries. That interoperability is what makes it possible to adopt Kotlin gradually inside an existing Java codebase rather than rewriting everything at once.

Because Kotlin compiles to JVM bytecode, and also targets JavaScript and native binaries through Kotlin Multiplatform, the skills carry across Android apps, backend services with frameworks like Ktor and Spring, and shared business logic across platforms.

The Kotlin Roadmap

Work through these in order, then pick a platform or framework that matches the direction you want to go

STEP 1

Introduction & Setup

Why Kotlin exists, where it came from, and getting a project running.

Documentation

Why use Kotlin History of Kotlin Java Interoperability Setting up the Environment Code Organization main Function Comments

STEP 2

Language Basics

Variables, basic types, and how Kotlin prints and formats data.

val vs var Variables Type Inference Integers & Unsigned Integers Floats Booleans Characters Strings String Templates Arrays print & println Type Checks & Casts Basic Types

STEP 3

Control Flow & Exceptions

Branching, looping, ranges, and handling things that go wrong.

if / when for while Label Loops break & continue Ranges Progressions Throwing Exceptions Catching Exceptions

STEP 4

Functions & Lambdas

Kotlin's function-first tools, from simple parameters to higher-order functions.

Parameters varargs Local Functions Member Functions Extension Functions Anonymous Functions Lambda Functions Higher-order Functions Function Types Tail-recursive Functions return & Standard functions

STEP 5

Collections & Sequences

Lists, sets, and maps — and the operations that filter, group, and transform them.

Documentation

Lists, Sets & Maps Read-only vs Mutable Sequences Iterators Transformations Filtering Retrieving Collection Parts Retrieving Single Elements plus & minus Operators Ordering Grouping Aggregate Operations

STEP 6

Classes & Objects

Modeling data and behaviour with Kotlin's class system.

Defining Classes Creating Instances Class Members Properties & Methods Constructors Inheritance Abstract Class Interfaces Visibility Modifiers Nested & Inner Classes Object Declarations Property Delegates Data Classes Sealed Class Enum Class Inline Class Class Generics Type Aliases

STEP 7

Null Safety

Kotlin's built-in defense against the "billion-dollar mistake."

What is Null Safety? Nullable vs Non-nullable Nullability Check Operators Safe Casts

STEP 8

Coroutines & Async Programming

Kotlin's approach to concurrency, built around lightweight suspendable functions.

Suspending Functions Coroutines Builders Coroutines Behavior Asynchronous Flow Coroutines Best Practices

STEP 9

Packages, Ecosystem & Build Tools

Organizing code into packages, pulling in libraries, and building the project.

Understanding Packages Importing Packages Standard Library Default Imports Opt-in Requirements Gradle & Gradle Plugins Maven Build Tool API Test Library Serialization I/O Library Date & Time JVM Metadata Documentation: Dokka & KDoc CI/CD: TeamCity Creating Files Writing & Reading Files Buffered Streams

STEP 10

Kotlin Platforms & Java Interop

Taking Kotlin beyond the JVM, and moving fluently between Kotlin and Java code.

STEP 11

Frameworks, Tools & Android

Where Kotlin lands in real applications — servers, IDEs, data, and mobile.

GitHub Projects

Real, buildable projects to put on your own GitHub

Kotlin Koans

Work through a series of small, hands-on exercises covering language basics, collections, and functions — built by JetBrains specifically to teach idiomatic Kotlin.

Language Basics Exercises Fundamentals

Ktor Backend Samples

Fork one of the official Ktor sample projects and extend it into a small REST API to practise routing, serialization, and coroutines together.

Ktor REST API Coroutines

Android Sunflower

Study Google's official gardening-app sample to see idiomatic Kotlin, Android Jetpack, and modern app architecture used together in a real codebase.

Android Jetpack Sample App

kotlinx.coroutines Examples

Read through the official coroutines library and its examples to lock in suspending functions, builders, and asynchronous Flow from step 8 of the roadmap.

Coroutines Async Flow

Frequently Asked Questions

Common questions from people starting out with Kotlin

Is Kotlin easy to learn?

Kotlin is generally considered approachable, especially if you already know Java — the syntax is more concise and many rough edges are smoothed over. Coming from scratch, expect a learning curve around null safety, coroutines, and the functional-style collection operations.

Why do developers switch to Kotlin from Java?

Kotlin cuts down on boilerplate, adds compile-time null safety to catch a whole class of bugs early, and includes coroutines as a first-class way to write asynchronous code — while still compiling to the same JVM bytecode and interoperating directly with existing Java code.

Do I need to learn Java before Kotlin?

No — Kotlin is designed to be learned on its own. Knowing Java helps you recognize JVM concepts faster, but Kotlin's own documentation and this roadmap assume no prior Java experience.

Kotlin vs Swift — how do they compare?

Both are modern, statically typed languages with null safety built in, and both are the preferred language for their platform — Kotlin for Android, Swift for iOS. Kotlin also compiles to the JVM and JavaScript, while Swift is tied more closely to Apple's own toolchain.

Is Kotlin only for Android development?

No. Android is Kotlin's most visible use case, but it's also used for backend services with frameworks like Ktor and Spring, for scripting, and for shared logic across platforms through Kotlin Multiplatform.

How do I prepare for a Kotlin interview?

Be comfortable explaining null safety and the nullability operators, data classes vs regular classes, and how coroutines differ from threads. Practise the collection operations (filtering, mapping, grouping), and have a small project you can walk through in detail.

Track complete

From language basics to coroutines and the frameworks built on top of them — that's the core of what employers expect from a Kotlin developer. Keep building, and let the platform you enjoy most (Android, server-side, or multiplatform) pull you toward the next roadmap.

Where next?

Keep exploring by domain or drill into a single skill

Browse by Domain

Role-based roadmaps like Android, Backend, and Full-Stack Developer.

Browse by Skill

Go deep on one tool at a time — Ktor, Spring, Gradle, and more.