Welcome to the Java world. This was designed to be for students in a robotics program that have some programming experience. Usually on our team, students will have looked at CircuitPython already. Python is a bit easier to start with. However, we use Java on the Robot. These examples are to help get you started with Java.
For more, information see the github wiki for this project.
The workspace contains one folder by default, where:
src\examples: the folder has all the examples- The folders start with a letter to keep in order, and then the name, so a_helloworld is the first example folder. It likely contains a file called HelloWorld.java. Some of the later folders have more than one file/program in them.
There are two possible editors you can use. VSCode with some Java extensions, and IntelliJ. The official plugin for building/sending code to the robot that is supplied from first is for VSCode. See your mentors for hlep installing an editor.