Disapearing code O_O

I keep writing up code files with Java. I'm making a game for a class I'm in, and every time I restart the computer AFTER SAVING, the code file deletes all the text in it. Netbeans says it has invalid characters, so I think it changed all my code to a blankpost character....

T_T how do I get it back i needs it? and what is wrong? how do i fix it?

Thanks

One time I was working on a game in the Arduino IDE. I compiled and uploaded to the Arduino chip, at which point my computer froze. I force restarted and went back to my code, and found it completely replaced with 17kb worth of null characters.

FUCK ARDUINO.

How could this have been possible? Why is my source code being opened with a write-enabled stream? Am I missing something?