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.
Well, none of these methods is throwing an exception (an oversight by my side, too).
You should try using new Files.delete(Path) (the class introduced in JDK 7). If something fails, you will get appropriate exception so you can know what went wrong. Check this tutorial.