Becareful with the method names. For example, if you override the service() methods in your servlet class, you will lose the functionality provided by the HttpServlet Class and the doXXX methods will not be called automatically
You can use methods in a servlet just the way you would use it a normal Java class. Quite a few times (make that most of the times if you wish), you will need to a few operations within your request handler methods. There is nothing to stop you from writing a method, public or private according to your app design, and calling it from your service methods.
However, as Gregg has rightly pointed out, having Java classes with specific responsibilities is way much better OOP. Service methods can use these objects to process user requests.
The bottom line is, yes you can definitely use methods inside your servlets just the way you do in normal Java classes
Vijayendra <br /> <br />"The harder you train in peace, the lesser you bleed in war"