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From "Georg Henzler (Updated) (JIRA)" <>
Subject [jira] [Updated] (IO-288) Supply a ReverseFileReader
Date Fri, 04 Nov 2011 16:45:51 GMT


Georg Henzler updated IO-288:


Attached simple maven project with java class and unit tests.
> Supply a ReverseFileReader
> --------------------------
>                 Key: IO-288
>                 URL:
>             Project: Commons IO
>          Issue Type: New Feature
>          Components: Utilities
>            Reporter: Georg Henzler
>         Attachments:
> I needed to analyse a log file today and I was looking for a ReverseFileReader: A class
that behaves exactly like BufferedReader except that it goes from bottom to top when readLine()
is called. I didn't find it in IOUtils and the internet didn't help a lot either, e.g.
is a fairly inefficient - the log files I'm analysing are huge and it is not a good idea to
load the whole content in the memory. 
> So I ended up writing an implementation myself using little memory and the class RandomAccessFile
- see attached file. It's used as follows:
> int blockSize = 4096; // only that much memory is needed, no matter how big the file
> ReverseFileReader reverseFileReader = new ReverseFileReader(myFile, blockSize, "UTF-8");
// encoding is supported
> String line = null;
> while((line=reverseFileReader.readLine())!=null) {
>   ... // use the line
>   if(enoughLinesSeen) {
>      break;  
>   }
> }
> reverseFileReader.close();
> I believe this could be useful for other people as well!

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