Renaming a file from java

Hello,
I want to rename a file from a Java Application and I want this operation was very speed.
I would renaming was "atomic".... not interruptable from Operative System.
I made this operations in two ways: does anyone explain me if one of these is more efficient than the other one?
Thank you very much all in advance
Diego
First implementation
                        String tmpStateName = stateFname + ".tmp";
                        tmpStateFile = new File(tmpStateName);
                        tmpStateFileStream = new FileOutputStream((tmpStateFile));
               pd.store(tmpStateFileStream, "System shutdown");
                        tmpStateFile.renameTo(new File(stateFname));
Second implementation
                        String stateFnameTmp = stateFname + ".tmp";
               pd.store(new FileOutputStream (stateFname + ".tmp"),
               "System shutdown");
                        String command = "mv " + stateFnameTmp + " " + stateFname;
                        Runtime.getRuntime().exec(command);
....

But calling exec method of Runtime could I be faster
than the first implementation??
I thought that the first implementation was heavier
(more Java objects created) than the second one...
Was I wrong?Maybe.
However it is not relevent. It is just flat out stupid to make things that convoluted in the name of "performance". Especially something like this. All you are really doing in the second implementation is creating a brittle, unmaintable nightmare.
So don't do that.
Last but not least I would highly suspect that the first implementation will be faster anyway. You don't seem to be counting on the expense of creating a new process which is not "light" relatively speaking.

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