Setting Up IntelliJ IDEA

Why IntelliJ IDEA?

IntelliJ IDEA is JetBrains' own IDE, and because JetBrains also created Kotlin, IntelliJ offers the most complete Kotlin support: instant error checking, auto-completion, refactoring tools, and an integrated debugger.

Note: The free Community Edition fully supports plain Kotlin/JVM projects like the ones in this course.

Example: Why IntelliJ IDEA?

fun main() {
    println("IntelliJ IDEA gives instant feedback while you type Kotlin")
}

Creating a New Kotlin Project

From the Welcome screen, choosing New Project -> Kotlin lets you pick a build system (Gradle or IntelliJ) and a JDK. A minimal Kotlin/JVM console project needs nothing more than that to start running code.

Example: Creating a New Kotlin Project

fun main() {
    println("A new Kotlin project created in IntelliJ IDEA")
}

Running Code with the Green Arrow

IntelliJ shows a small green triangle next to any fun main() function; clicking it compiles and runs that file immediately, showing output in the Run panel at the bottom of the window.

Note: Shift+F10 (or Ctrl+R on macOS) reruns the last executed configuration without touching the mouse.

Example: Running Code with the Green Arrow

fun main() {
    println("Click the green run arrow next to main() to execute this")
}

Using Code Inspections

IntelliJ underlines problematic code in red (errors) or yellow (warnings/suggestions) as you type, and Alt+Enter opens quick-fixes for many of them, such as adding a missing import or simplifying an expression.

Example: Using Code Inspections

fun main() {
    val message = "IntelliJ suggests fixes with Alt+Enter"
    println(message)
}