This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
Do you mean you need to implement a sorting algorithm? Or can you use the built-in sort methods from the Java API? If you are interested in using the API, look at the java.util.Arrays class in the documentation (see the link in my signature). You may also want to use the reverseOrder() method from the java.util.Collections class.
What have you tried so far? Please give some details so that we can help you.