Java EE (Java Enterprise Edition) General Discussion

Although we had conceptually an abstract Class can't be instantiated even as Derived Class must implement/override all method of an abstract Class,but I have a doubt in employing of both GenericServlet and HttpServlet Class,are as follows.
(1)Even if we can implement GenericServlet/HttpServlet for the user- defined servlet class,that servlet may override merely doGet(),doPost().etc,but not all methods.

(2)How will happend when a Servlet Class implement GenericServlet/HttpServlet,and we aren't stipulating that servlet class as abstract.

May anybody steer me plz?

With Regards
Stalin.G