Read : Mughal book really well.
Read Marcus Green tutorial at last minute:-)..It'll give you confidence. If you read a very detailed material at the end, you'll get confused.
Read Velmurugan notes if you can.
My experience :
Questions really test your fundamentals. In threads there is lot of stress on synchronisation etc. (What will happen when 2 threads act on the same object...) In I/O the stress is on constructors. Collection,AWT etc is easy to answer. I made mistakes in Inner classes. Bit-shifting etc is easy stuff so just know the fundamentals in that..
I would say most of the mock exams(not that I tried many!!) are not similar to real test. On the other hand, some of the exam questions are really easy. There is no real time pressure also. I had 30 minutes to review all my answers.
All the best to everybody. My next goal is UML.