Installing and configuring IntelliJ IDEA, JDK 25

1. Why does a Kotlin developer need a JDK?

"But I’m learning Kotlin—why do I need to download Java (JDK)?". That’s an excellent question. To answer it, you need to understand how your code works.

Kotlin is a JVM language. This means it runs on top of Java technologies. Imagine a car:

• Kotlin is the body, the steering wheel, and a comfortable interior. It’s what you interact with.)
• JVM (Java Virtual Machine) is the engine that makes everything move.
• JDK (Java Development Kit) is the factory that produces that engine.

Without the “engine” (JVM), your beautiful Kotlin code simply won’t go anywhere.

How does it work technically?

When you click the “Run” button in IntelliJ IDEA, the following happens:

JDK contains JVM + a set of standard libraries used by both Java and Kotlin.

Why is it important to use a current JDK version?
Kotlin evolves very quickly and relies on new JVM capabilities. Version 25 brings performance improvements and new instructions for the “engine”, which makes your Kotlin code run faster and use less memory.

2. Downloading and installing the JDK

There are several official sources: Oracle, OpenJDK, Amazon Corretto. But right now we don’t need to download them manually via a browser.

We will delegate this task to IntelliJ IDEA. It will download the required version itself, unpack it into the correct folder, and set all paths. We will do this when creating the first project.

For our course, we will use the Amazon Corretto distribution. It is a reliable, free JDK build that handles non-Latin characters in paths well (although it’s still better to name folders using Latin characters!).

3. Downloading and installing IntelliJ IDEA

JetBrains official website: https://www.jetbrains.com/idea/download/

On the download page, the site will detect your OS automatically. You can select it manually if needed.

Previously, developers had to choose between the paid Ultimate and the free Community Edition at download time. Starting with version 2025.3, the process became simpler.

You download a single installer. Inside the program, you can use the free functionality (Community), which is 100% sufficient for learning Kotlin. If IDEA offers a trial period for Ultimate, you can accept or decline—it’s not critical for our course.

Installing IntelliJ IDEA on Windows

1. Download the .exe installer. Important: choose the CPU architecture (x64 or ARM64), although the site usually detects this automatically.
2. Run the file.
3. At the Installation Options step:
   • Check Create Desktop Shortcut.
   • Check Update PATH variable (requires a reboot, but it’s useful).
   • In file associations, select Kotlin for .kt.
4. Wait for the installation to finish.

Installing IntelliJ IDEA on macOS

1. Download the .dmg file. Attention: choose the correct chip!
   • Apple Silicon (M1, M2, M3...) — for modern Macs.
   • Intel — for older models.
2. Open the file and drag the IntelliJ IDEA icon into the Applications folder.

Installing IntelliJ IDEA on Linux

1. Download the .tar.gz archive.
2. Extract the archive to a convenient location, for example, ~/programs/idea.
3. Go to the bin folder and run the script: ./idea.sh
4. For convenience, you can create a shortcut via the menu: Tools -> Create Desktop Entry.

4. First launch and setup

After installation, IntelliJ IDEA will offer to import settings. If you’re installing it for the first time, choose Skip import.

Projects tab

This is the “Welcome Screen” start window.

• New Project — create a new project from scratch.
• Open — open an existing project (folder).
• Clone Repository — download a project from GitHub or GitLab.

Customize tab

This is where the appearance is configured. I recommend checking this right away.

• Color theme: choose a theme (Dark, Dracule or Light). Pick the one that makes your eyes less tired.
• IDE font: the UI font size.
• Language: leave it as English! All guides will be in English.

Everything is ready! In the next lecture, we will create your first Kotlin project.