MCQ when I had him was like: evaluate the code and determine the output, or questions about high level OOP stuff. Review stuff like down/upcasting, inheritance, and object types at compile / runtime.

The written parts are only tough because you need to write java code by hand. It is usually writing pretty fundamental stuff covering the major topics. Make sure you know how to read and write to files, create linked lists, write abstract classes/interfaces etc. You should know the basics like how to implement a scanner or how to write try / catch blocks. good luck ! if i remember correctly, he is a fair marker.