syntel interview questions

1. How do you manage session?
2. Difference between hashmap and hashset?
3. Difference between include and forward?
4. Difference between forward and sendredirect?
5. can abstract class contain concrete methods(one with implementation)? if yes then why to make that class abstract and not simple java class?
6. why do we use/need session beans?
7. which jdbc driver you have used?
8. To check object's uniqueness which methods we need to override?
9. How many times servlet's init() method is called in it's one lifecycle?
10. Can we call servlet's destroy() method from init() method?
11. Can we control number of servlet instances created by container?