You need to convert the found resource to URI. It works on all platforms and protects you from possible errors with paths. You must not worry about how full path looks like, whether it starts with ‘\’ or other symbols. If you think about such details – you do something wrong.
ClassLoader classloader = Thread.currentThread().getContextClassLoader();
String platformIndependentPath = Paths.get(classloader.getResource(errorFile).toURI()).toString();