If the identical code functions on just one Computer, but it surely shows the error in Yet another, the best Answer I've ever uncovered is compiling like the next: all classes and interfaces in the superclass hierarchy (e.g. see Java course is existing in classpath but startup fails with Error: https://judo-sport49269.csublogs.com/40751399/the-definitive-guide-to-uninterruptible-power-supply-calculator