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.
File.mkdir and File.mkdirs, along with File.delete and File.renameTo, return boolean to indicate success rather than throw an exception. This can be annoying since it doesn't tell you the reason why the operation failed. At least with the upcoming java.nio.file.Path class that has been solved, with the following replacements:
File => File.toPath
File.delete => Path.delete
File.renameTo => Path.moveTo
File.mkdir => Path.createDirectory
File.mkdirs => java.nio.file.Files.createDirectories