Otherwise you could potentially quickly miss 1 line you don't want and acquire The end result which DrStrangeprk talked about. all lessons and interfaces while in the superclass hierarchy (e.g. see Java course is existing in classpath but startup fails with Error: Couldn't uncover or load primary class) For instance, https://dominicktzzxu.bcbloggers.com/32986894/uninterruptible-power-supply-ups-fundamentals-explained