Details

    • Type: New Feature New Feature
    • Status: Closed
    • Priority: Major Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 2.2
    • Component/s: Utilities
    • Labels:
      None

      Description

      I needed to analyse a log file today and I was looking for a ReversedLinesFileReader: 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. http://www.java2s.com/Tutorial/Java/0180__File/ReversingaFile.htm 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 is
      ReversedLinesFileReader reversedLinesFileReader = new ReversedLinesFileReader (myFile, blockSize, "UTF-8"); // encoding is supported
      String line = null;
      while((line=reversedLinesFileReader.readLine())!=null) {
      ... // use the line
      if(enoughLinesSeen)

      { break; }

      }
      reversedLinesFileReader.close();

      I believe this could be useful for other people as well!

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          • Assignee:
            Unassigned
            Reporter:
            Georg Henzler
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            Dates

            • Created:
              Updated:
              Resolved:

              Development