Java Interviewing

what is major concepts in oops?
answer: polymorphism, encapsulate, inheritance
what common methods are defined in object class?
answer: hashCode(), equals(), toString(), clone(), finalize(), getClass(), wait(), notify(), notifyAll()
what is differenec between abstract class and interface?
answer: In abstract class some methods may contain definition,but in interface every method should be abstract.
what is differenec between overload and override?

what is implicit object in jsp?
how many implicit objects in jsp?
answer: Implicit objects are a set of Java objects that the JSP Container makes available to developers in each page
out,page,session,request,response,application,page context,config

what is main difference hashmap and hashtable?
answer: hashtable is synchornized.

what is immutable and how to implement it?
answer:it can’t be changed.

what is the factory, abstract factory, factory method?
draw them on the white board.
How to implement a singleton?
answer: make constructor privated, and provide a method to return single object shared in application.

How to deal with the transaction across databases?what is 2PC?
answer: two-phase commit

what should pay attention in development if we use junit?
independence of each tested classes.

which UML diagrams are often used in a project?

what is CMMI? what levels are defined in it?
initial, managed, defined, quantitativly managed, optimism.