This week's book giveaway is in the Java 9 forum. We're giving away four copies of Java 9 Modularity: Patterns and Practices for Developing Maintainable Applications and have Sander Mak & Paul Bakker on-line! See this thread for details.
I'd suggest more sticking to the released versions of Enterprise Edition (much like the requirements for SCJD) at least for the time being. I suppose it depends greatly on when you're aiming to have the assignment done, though.
But, by and large, you can use any version you want, from what we've seen.
Theodore Jonathan Casser
SCJP/SCSNI/SCBCD/SCWCD/SCDJWS/SCMAD/SCEA/MCTS/MCPD... and so many more letters than you can shake a stick at!