Firstly, there will be an aptitude test where you will be given 50 questions and they should be solved in one hour. Quant section is pretty much tough. You need to refer materials to solve the above. Verbal and logical are easier when compared to the above. Later, communication assessment round, where you need to repeat the sentences that were told to you on the phone, there itself. Listen carefully and reply, or you will blow your interview. Later, technical interview. Be perfect in basics, and it's more than enough. Later, HR round for seeing your personality.

Anything about Java, mostly basics like JVM architecture, JIT compiler and interpreter, garbage collector, hash files, HotSpot, heap, etc. Refer to Herbert Schildt.