Pregunta de entrevista de Deloitte

Basic core java questions 1.What are abstract classes?? write syntax? 2.In what package regex is? 3.Explain MVC? 4.Where servelet mapping of url exist? 5.How do you rate your self in core java?? 6.Difference between application server and webserver? 7.What is generic servlet?How it is different from http servelet???