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 navi-3dmap-location-search-10.0.700_3dmap10.0.700_loc6.4.5_sea9.7.2.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.
