Design Patterns Interview Questions

Design Patterns Interview Questions

(1) What are design patterns?

Design patterns are some standard rules which are used to do certain tasks.Design patterns are used to build designs to increase the performance and to make our applications more robust.

(2) What is front controller design pattern?

It is the first component that handles the user request.It authenticate, authorize the user.it tells that whether user is logged on or not.it is centralized  controller for handling user request.in struts 1.2 ActionServlet is front controller.In spring mvc DispatcherServlet is front controller.

(3) Which design pattern is followed by session class?

Factory design pattern .since it is the factory of transactions.

(4) What is bridge design pattern?

One interface and many implementations describes bridge design pattern. jdbc is the best example of bridge design pattern because it is set of interfaces and these interfaces are implemented by many driver classes.

(5) Why we use business delegate pattern?

It is implemented by business delegate classes.it is used to decouple the business layer and presentation layer.It is used in presentation layer but works on business layer.

(6) What is factory design pattern?

It creates and return instance of one or several possible classes depending on the parameters provided to it.it is implemented by service locator class, daofactory class,etc.

(7) What is singleton design pattern?

In this pattern only one instance of the class is created for whole application.it is implemented by daofactory class , service locator class,etc.