One build command
A good repo is not just source code. It has a build tool so another builder can clone it and run one clear command.
Use Maven or Gradle. For this track, Maven is the simpler default because many Java examples and college labs already use it.
What Maven does
Maven reads a file named pom.xml. That file tells Maven your Java version, dependencies, and how to compile the app.
You do not need to install every library by hand. If your project uses a JSON library, Maven downloads it from its central repository during the build.