Groupon Principal Engineer interview questions

I got the interview call via a consultant. It was the worst experience I had in the entire career. Primarily because I felt the HR is very unprofessional. It was a whole day process and they made me wait till 2.45 pm noon and did not bother to arrange lunch. That's the last thing you expect when you go to a company for the interview process. The First round was more on problem-solving and technology. Some questions where really surprising like "what is j2ee" !!! Then there were programming and problem solving questions. I felt that the interviewer was not open for discussion and was expecting some answers he had in mind. (I am perfectly fine with it.) The Second round: it seems the interviewer was not interested in meeting candidate. He rushed in and did not even bother to introduce himself. I solved the problem given to me but again I felt that interviewer had some answer in mind and he was expecting same. The second round got over in 35 mins and I was asked to wait till someone arranges lunch. I waited from 1.15 to 2.15 in the same meeting room and then after not seeing anyone around, I called HR. He told me he will be back in 2 min but again I had to wait till 2.40 pm. Finally he came to me when I called him again and told him that I am going out for lunch.!!! Third round: was the only quality round. The interviewer asked some good questions and was open to discussion. This is the only +ve experience I had in the entire process. Later I was told that they will get back to me with feedback since the panel has mixed feedback and they need to discuss with hiring manager who is busy right now. But they never got back.