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 believe they are loaded in the order in which they are added to server.xml. However, if you wanted, you could add a line of debugging to each application and check the log file entry's timestamp to see which loaded first.