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.
I recommend to send them yet an other email in which you include the MD5sum of your submission jar file. You can use jchecksum to compute it. This way you prove that you did not change it after taking the essay exam.
I recommend to go to the exam anyway and upload your project as soon as possible.