I have one question on the topic mentioned above
Which Java API shall we know by heart?
There was a case that in interview question interviewers stared grilling me on Thread and java.io API asking what are new things in Java 1.6
I was out of touch of latest in Java API and didn't do good
SCJP,SCWCD,SCBCD<br />If Opportunity doesn't knock then build the door
There are certain APIs that are always good to know. I would recommend studying:
1) Every method in the Object class
2) The different types of collections in the Java Collections Framework
3) The JDBC APIs
4) The Servlet APIs
5) Concurrency APIs (Both standard APIs like Thread and Runnable, and the newer Executor Framework)
6) The Reflection classes
File I/O is of course useful as well, but the new NIO features are a little more niche. I think you might benefit from a website that lists all of the new features that were released from 1.6 on and just read a little bit about each topic so you won't be caught off guard in future interviews. Even if you don't know them in detail, it will help to show that you are familiar with them.