Simple introduction to modules/Jigsaw in Java.
The sample code to illustrate the talk http://bit.ly/JigsawWrocJUG-slidez
I suggest checking out tag "start" first, then checking out steps 01 to 11, e.g.
git checkout start
git checkout step01
git checkout step02
...
git checkout step11
At each step try running ./gradlew run and ./script.sh to see what happens. Java 11 required.