asciidoctorj-diagram-plantuml
· AsciidoctorJ Diagram Plantul bundles the Asciidoctor Diagram Plantuml RubyGem (asciidoctor-diagram-plantuml) so it can be loaded into the JVM using JRuby.
Download JD-GUI to open JAR file and explore Java source code file (.class .java)
Click menu "File → Open File..." or just drag-and-drop the JAR file in the JD-GUI window asciidoctorj-diagram-plantuml-1.2023.5.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.