Persistence Class - need advice

I've coded up a persistence class for some of my plugins to store a couple HashMaps of miscellaneous data in binary files for quick IO when starting up and stopping the server. It seems to work, but I had to suppress a lot of warnings and I would like a more experienced programmer to see if I did anything glaringly wrong. I didn't know of a way to check casts inside of a generic class like this one, but the only objects that can be in the file, the way I understand it, are going to be the right type because of the generics. I'd really like to know what the hiding warning is all about. I couldn't find anything on that anywhere. I've posted my code on pastebin, if you want me to post it here let me know and I'll do that later. Here's the pastebin link: http://pastebin.com/FhyTZDZk

Michael Briggs