Transactional File System in Java

If you have to operate on files and cannot afford to loose data, seriously consider using one of the available frameworks. If you search the net, you come a cross some. One of the best is the Apache commons-transactions package. And of course it is probably better then any custom mechanism you can come up with.
Found this blogpost about using commons-transactions today. It is a step by step description about installation and ussage. Give it a try!