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Introduction to Kotlin: Where to Start in 2025
Kotlin is a modern, statically typed programming language developed by JetBrains. In 2025, it firmly holds a position as one of the most in-demand languages, especially in Android development (Google officially recommends Kotlin), as well as for backend development, desktop, and multiplatform applications. If you are a beginner and want to enter IT in 2025, Kotlin is an excellent choice: it is concise, safe, and has a huge community.
In this article, we will break down where to start learning Kotlin in 2025, how to set up the development environment, write your first program, and master the basic syntax.
Why Choose Kotlin in 2025?
Kotlin solves many problems inherent in Java while remaining fully compatible with it. Here are the key reasons to start learning Kotlin right now:
- Official Android Language: Google has declared Kotlin the priority language for Android development.
- Multiplatform (KMP): Kotlin Multiplatform allows you to write shared code for iOS, Android, Web, and Desktop.
- Null Safety: The built-in type system protects against NullPointerException, one of the most common errors.
- Conciseness: Code in Kotlin is on average 30-40% shorter than equivalent code in Java.
- Modern Features: Coroutines for asynchrony, Data classes, lambdas, extension functions.
Step 1: Installing Tools in 2025
Installing IntelliJ IDEA
The best development environment for Kotlin is IntelliJ IDEA Community Edition (free). Download it from the official JetBrains website.
Installing JDK
Kotlin runs on the Java Virtual Machine (JVM). You will need JDK 17 or newer. We recommend OpenJDK or Oracle JDK.
Verifying Installation
After installation, open IntelliJ IDEA, create a new project, select "Kotlin" and "Console Application". Done!
Step 2: First Program in Kotlin
Let's write the classic "Hello, World!" and break it down.
// This is a commentfun main() { println("Hello, World!") println("Welcome to Kotlin 2025!")}Code Breakdown:
fun— keyword for declaring a function.main()— the entry point of the program.println()— function for printing a string to the console.//— single-line comment.
Run the program (green triangle to the left of the code). You will see the greeting in the console.
Step 3: Kotlin Syntax Basics for Beginners
Variables: val vs var
Kotlin has two types of variables:
val— immutable (read-only). Cannot be reassigned.var— mutable. The value can be changed.
fun main() { val name: String = "Anna" // Immutable var age: Int = 25 // Mutable
// name = "Olga" // Error! val cannot be changed age = 26 // Works
println("Name: $name, Age: $age")}Output: Name: Anna, Age: 26
Notice the string interpolation — the $ symbol allows you to insert variables directly into the string.
Data Types
Kotlin is a statically typed language, but types can often be omitted — the compiler will infer them.
| Type | Description | Example |
|---|---|---|
Int | Integer number | val x: Int = 10
|
