Efficiently Running UNIX des command from Java

Hi,
I am trying to execute the following code in a loop to have an Brute Force attack for recovering the key.
Runtime r = Runtime.getRuntime();
p = r.exec("des -D -k "+keys.get(randomIndex)+ " " +cipherTextFileName);
But as the des command has to read the file every time the programm is not a efficient one.Can I do something like reading the ciphertext from the file only once and then pass it to the des command from the java.So that it won't do I/O operations resulting good performamnce.If I can do this how to do it.Please suggest with examples.
Thanks
Tapas

If you use Java you're not doing that. What does being an Academic project have to do with what tools you're allowed to use? Who is dictating that you're "only" allowed to use the des command line tool? (If it comes to that, which des command line tool are you using anyway? It's not a unix standard thing).
The one thing you can do is to see if there is an option to read the file(s) from standard input and send them to the process from the Java runtime that way - that way the input doesn't have to be read multiple times. However this is unlikely to make any significant difference. Most of the performance cost is likely to be the context switch required to kick off the new process with very little cost incurred from re-reading a file from the disk cache.
You've got your answer anyway. You're not going to be able to make this much more efficient. I recommend not doing that. If you really really have to, well, tough.

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--- Code ---
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