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.
If you have to ask, it probably isn't needed in your application. Seriously, warnings aren't looked at in most business applications. The first example that comes to mind is an application that troubleshoots database connections.