Introduction to Kotlin: Where to Start in 2025

Introduction to Kotlin: Where to Start in 2025

Kotlin is a modern statically typed programming language that runs on the JVM (Java Virtual Machine) platform and is actively developed by JetBrains. In 2025, Kotlin has firmly established itself as one of the most in-demand languages for developing Android applications, server-side solutions, and cross-platform projects. If you are wondering where to start learning Kotlin, this article will be your first step.

Unlike many other languages, Kotlin combines code writing simplicity with high performance and full compatibility with Java. Thanks to its concise syntax and powerful tools such as null safety and coroutines, Kotlin allows you to write safer and more readable code with fewer errors.

Why Choose Kotlin in 2025?

Before moving on to technical details, it is important to understand why Kotlin has become so popular. Here are the main reasons:

Official language for Android: Google has declared Kotlin the priority language for Android development. All new Android libraries and tools are primarily oriented towards Kotlin.
Compatibility with Java: You can use any Java libraries and frameworks in Kotlin projects. This allows you to gradually migrate from Java to Kotlin without rewriting all the code.
Cross-platform: With Kotlin Multiplatform, you can write shared code for Android, iOS, web, and desktop, which significantly saves development time.
Safety and conciseness: Kotlin code is on average 30-40% shorter than equivalent Java code, and the type system prevents many errors at the compilation stage.

Step 1: Installing and Setting Up the Environment

To start working with Kotlin, you will need an Integrated Development Environment (IDE). The most popular choice is IntelliJ IDEA Community Edition (free version) from the same developers, JetBrains. It includes full Kotlin support out of the box.

An alternative option is Android Studio, if your goal is mobile application development. For simple experiments, you can use the online compiler Kotlin Playground on the official website.

Installing IntelliJ IDEA:

Download the installer from the official JetBrains website.
Run the installation, selecting the Community version (free).
After installation, create a new project: File → New → Project.
Select the language Kotlin and the build system Gradle (Kotlin DSL).

Done! Now you have a working environment for writing Kotlin code.

Step 2: Kotlin Syntax Basics

Let's break down the key elements of the language that a beginner needs to know.

Variables and Data Types

Kotlin has two keywords for declaring variables:

val — an immutable variable (analogous to final in Java). The value cannot be changed after assignment.
var — a mutable variable. The value can be reassigned.

fun main() {    // Immutable variable (recommended to use by default)    val name: String = "Kotlin"        // Mutable variable    var age: Int = 2025    age = 2026 // OK        // Output to console    println("Hello, $name! Current year is $age")}

Note the string interpolation: the $ symbol allows you to insert variable values directly into the string.