OWLAPI
· The OWL API is a Java API and reference implementation for creating, manipulating and serialising OWL Ontologies. The latest version of the API is focused towards OWL 2
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 owlapi-parent-3.4.9.2-ansell.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.