Kotlin/JVM 入门

This tutorial demonstrates how to use IntelliJ IDEA for creating a console application.

To get started, first download and install the latest version of IntelliJ IDEA.

Create a project

  1. In IntelliJ IDEA, select File | New | Project.
  2. In the panel on the left, select New Project.
  3. Name the new project and change its location if necessary.

    Select the Create Git repository checkbox to place the new project under version control. You will be able to do it later at any time.

  4. From the Language list, select Kotlin.

    Create a console application

  5. Select the IntelliJ build system. It's a native builder that doesn't require downloading additional artifacts.

    If you want to create a more complex project that needs further configuration, select Maven or Gradle. For Gradle, choose a language for the build script: Kotlin or Groovy.

  6. From the JDK list, select the JDK that you want to use in your project.

    • If the JDK is installed on your computer, but not defined in the IDE, select Add JDK and specify the path to the JDK home directory.
    • If you don't have the necessary JDK on your computer, select Download JDK.
  7. Enable the Add sample code option to create a file with a sample "Hello World!" application.

  8. Click Create.

Create an application

  1. If you chose the Gradle build system, you have build.gradle(.kts), a build script file, in your project. It includes the kotlin("jvm") plugin and dependencies required for your console application. Ensure that you use the latest version of the plugin:

    plugins {
        kotlin("jvm") version "1.6.21"
        application
    }
    
  2. Open the main.kt file in src/main/kotlin.
    The src directory contains Kotlin source files and resources. The main.kt file contains sample code that will print Hello World!.

    main.kt with main fun

  3. Modify the code so that it requests your name and says Hello to you specifically, and not to the whole world:

    • Introduce a local variable name with the keyword val. It will get its value from an input where you will enter your name – readln().

      The readln() function is available since Kotlin 1.6.0.
      Ensure that you have installed the latest version of the Kotlin plugin.

    • Use a string template by adding a dollar sign $ before this variable name directly in the text output like this – $name.

    fun main() {
        println("What's your name?")
        val name = readln()
        println("Hello, $name!")
    }
    

    Updated main fun

Run the application

Now the application is ready to run. The easiest way to do this is to click the green Run icon in the gutter and select Run 'MainKt'.

Running a console app

You can see the result in the Run tool window.

Kotlin run output

Enter your name and accept the greetings from your application!

Kotlin run output

恭喜! 你现在运行了第一个 Kotlin 应用程序。

下一步做什么?

Once you’ve created this application, you can start to dive deeper into Kotlin syntax: