The servlet programmers typically don't want their servlet to support the main HTTP methods (POST, GET), so it would be annoying to make the doGet(), doPost(), etc. methods abstract, since programmers would be forced to implement methods that they don't need. Therefore, HttpServlet provides a default implementation for all those methods that does nothing except return an error statuscode to the client. Programmers can override the methods they need. But actually using the HttpServlet class itself make no sense, so it is called as abstract.