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.
POI is just an API to read and write Excel files. You can use it to perform some simple manipulations, but nothing like sorting. That would be good addition, though, so if you get around to implementing it, you might consider contributing the code to the project