The important areas one must know for Job Interviews are:
- Core Java Concepts (you can expect these questions even after 4 years)
- OO Concepts (try to develop practical experience all these concepts and impress by writing code in front of an interviewer)
- JSP and Servlets (life cycle methods, difference between GenericServlet and HttpServlet, Session handling, Cookies, URL-rewriting, annotations, Servlet filters, web.xml vs. annotations, JSP rags.. etc)
- Multithreading, concurrency and thread basics
- Usage of abstract class and interface
- User defined custom exceptions and its advantages
- String vs. StringBuffer vs. StringBuilder
- Java Collections (util package)
- Exception handling
All the best 👍