This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
The only difference is that in the first your reference to the context expires at the end of your synchronised code block. But I don't see how knowing this or not knowing it would help or deter you in the exam.