They asked questions on Java cocepts like : OOPS, Multithreading, Collections. They will show you code snippet, you have to tell the output and with that you will have to discuss the above topic in depth with interviewer. They will usually ask edge cases. Ex: What if we implement 2 interfaces having same name and same signature for a default method. How to solve this problem. Ex2: Why we can create constructor in abstract class but we cannot initialize it. Why java introduced this? Ex:3 What if we override equals method and hashcode method. What if we are returning same value from hashcode method and always returning false from equals method. Ex: 4 If in a class having two different methods with two synchronized blocks and two threads are accessing different methods, What will happen? who will wait?

What do you know about the Collection interface?