To compile the Java code, JOGL (Java Binding for the OpenGL API) is required.
https://jogamp.org/jogl/www/

1) Download JOGL from
https://jogamp.org/wiki/index.php/Downloading_and_installing_JOGL

2) Unzip jogamp-all-platforms.7z into the "java" directory, to produce the following directory structure:
java/jogamp-all-platforms
java/jogamp-all-platforms/jar
java/gsn

3) To compile the sources, open a command-line interface and run the following command from the "java" directory:
javac -classpath "./jogamp-all-platforms/jar/gluegen-rt.jar;./jogamp-all-platforms/jar/jogl-all.jar;." gsn/*.java
 
4) Run the program with:
java -classpath "./jogamp-all-platforms/jar/gluegen-rt.jar;./jogamp-all-platforms/jar/jogl-all.jar;." gsn/Main

LINUX:
For linux, the separator in the classpath is a colon instead of a semicolon. 
Consequently, the commands of step 3 and 4 are:
javac -classpath "./jogamp-all-platforms/jar/gluegen-rt.jar:./jogamp-all-platforms/jar/jogl-all.jar:." gsn/*.java
java -classpath "./jogamp-all-platforms/jar/gluegen-rt.jar:./jogamp-all-platforms/jar/jogl-all.jar:." gsn/Main

Alternatively, you can set up JOGL in your favorite_IDE:
https://jogamp.org/wiki/index.php/Setting_up_a_JogAmp_project_in_your_favorite_IDE




Please get in contact at https://www.gsn-lib.org if you have questions, requests, or suggestions for improvement.
Your feedback is very much appreciated.