Apache Jena - Distribution
· Apache Jena is a API and toolkit for working with semantic web technologies such as RDF and SPARQL using Java. This artifact represents the source and binary distribution packages generated for releases.
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 apache-jena-4.9.0.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.