1. Download Kobalt

Download the zip file then unzip it in a location we'll call KOBALT_HOME:

cd $KOBALT_HOME
unzip kobalt-xxx.zip

Note: Kobalt doesn't need any environment variable to run, the environment variable used above is only here for clarity.

2. Initialize your project

Change to your project directory and call the kobaltw command with --init:

cd ~/java/project
$KOBALT_HOME/kobaltw --init java

This command will do two things:

1. Create a default kobalt/src/Build.kt suitable for a brand new Java project.
2. Install the Kobalt Wrapper in your current directory (a script called kobaltw) and a few additional files in the kobalt/wrapper directory. From now on, you can just use ./kobaltw to build and you can ignore $KOBALT_HOME.

You can now attempt to build your project with Kobalt:

./kobaltw assemble

If your project follows a regular build structure (e.g. Maven's hierarchy), this should compile your file and create a .jar file. If not, you will have to make a few edits to your Build.kt. As of this writing, Kobalt supports Java and Kotlin projects.

3. Edit kobalt/src/Build.kt

The build file generated by default might need some editing before you can build your project, so take a look at it and adjust whatever is necessary (e.g. package name, version, etc...)

Here is the Build.kt for the JCommander project:

import com.beust.kobalt.*
import com.beust.kobalt.plugin.java.*
import com.beust.kobalt.plugin.packaging.*
import com.beust.kobalt.plugin.publish.*

val jcommander = project {
    name = "jcommander"
    group = "com.beust"
    artifactId = name
    version = "1.54"

    dependenciesTest {
        compile("org.testng:testng:6.9.9")
    }

    assemble {
        mavenJars {
        }
    }

    jcenter {
        publish = true
    }
}

4. Sync your build file

If you're using Intellij IDEA, make sure you've installed the Kobalt plugin and then go to Kobalt -> Sync Build File. Once the build file is synchronized, the errors should disappear and you can now use all the regular functions of IDEA on Build.kt just like any other Kotlin files (auto completion, jump to symbol, etc...).

5. Next steps

From this point, you can either learn how to install the Kobalt IDEA plug-in or read Kobalt's documentation.