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 babel__plugin-bugfix-v8-static-class-fields-redefine-readonly-8.0.0-alpha.6.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.
