how to change a file back to its normal state

[user1818]

how can I change a file back to its normal state because I tried to use a file with java and after that most of my files turned into java files. I tried to back up but its been affected with java. This also happened with changing it with another default program.

 

[SmithRO]

what do you mean by "files turned into java files"? are they now opened by default with java software?