Despite the other interviewees on here posting about Java questions being asked in their on-site interviews, don't be surprised now if they start asking you design questions. First the recruiter called me explaining to me about the company where they configure access privileges for multiple users in a network, i.e. a school or a big company and told me I would receive a phone call asking basic Java Questions. I received the phone call on a scheduled day and answered basically all of the questions correctly as it wasn't very difficult. I then received a phone call from the recruiter a couple of hours later scheduling me to go to their office and be asked some programming questions and concepts. When I did go on site, I was asked a single design question about designing a restaurant reservation booking system which although not difficult, kind of threw me in a loop because I did not know what kind of answer they were expecting and it felt more like an open-ended essay assignment in English class than a programming question. That was the only question they asked me that day, nothing Java or programming related. The recruiter had no technical background and didn't know what the person-to-person interview would actually be like, so study some Object Oriented Design in your preparation.