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.
There are a number of ways to do this depending on how clever you want to get. Check out the existing collection tags for info. Could also do something tricky via OGNL--check out the OGNL docs. Or just reverse it on the Java side.