Setting Up Your Development Environment

Kotlin is made by JetBrains, and its best editor support is in their IDEs:

• IntelliJ IDEA — for general Kotlin: command-line programs, back ends, and libraries.
• Android Studio — for Android apps.

Both give you autocomplete, instant error highlighting, refactoring, debugging, and one-click running.

Your first project in IntelliJ IDEA

1. File → New → Project, choose Kotlin, give it a name.
2. Choose Gradle as the build system (with the Kotlin DSL), and let it download a JDK if you don't have one.
3. Open src/main/kotlin/Main.kt and click the green ▶ next to fun main() to run it.

The output appears in the Run panel at the bottom of the window.

A build system (Gradle) compiles your code, downloads libraries, and runs tests. You don't need to understand it yet — Level 2 has a Gradle lesson.

Handy editor features

• Alt + Enter (⌥↩ on macOS) shows quick fixes for the code under the cursor — often exactly what you need when something is underlined.
• Inlay hints show the types Kotlin has inferred for your variables, which is a great way to learn how type inference works.