If Servet Inteface is implement in userdefind servlet than in what method can you write business logic?

In a user-defined servlet that implements the Servlet interface, you can write business logic primarily in the doGet() and doPost() methods. These methods handle HTTP GET and POST requests, respectively, and are where you can process input, interact with databases, and generate responses. Depending on the application’s requirements, you might also use helper methods to organize your business logic more effectively.