Edit files single line in java

I'm trying to edit configuration file in Java. What I really need to do is to change single line, so reading the whole file and writing it back would be waste of time, since configuration file ca开发者_C百科n be big.

Is there a more efficient way to do this? Except reading in/editing/writing out file. I thouhgt of converting entire file to string, replacing the line I want and writting it back.

I don't know how efficient would that be, can someone give me some other suggestions or the one I mentioned are ok, execution time is important.

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I would recommend to use the Preferences API instead. Then on the Windows platform your preferences is stored in the registry. On other platforms the corresponding way to save application preferences is used. See also Preferences API Overview.

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How big of a configuration file are we talking here? 1k lines? 10k? 1m lines? If the line you want to edit is the last line, just seek to the start of the line, truncate the file there and write the new one. If it's not... you will need to read it whole and write it again.

Oh, and the 2 options you mention are actually the same (read/edit/write).

On the third hand, I think it's irrelevant (unless you have weird constraints, like a flash storage device which takes too long to write, and has limited write cycles), given the sizes of most config files.