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Getting Only the End Content of a File in Java

Posted on 2006-06-25
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Last Modified: 2010-03-31
Hi everyone,

I was wondering if it was possible to get only the last 10K of a file content instead of reading the entire file to save memory.  Can anyone point me to the right direction, or maybe share some basic code that would do this?  That would be so cool.

Thank you so much,


Jazon from Fort Myers, FL
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Question by:piratepatrol
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Expert Comment

by:CEHJ
ID: 16979705
You can use a RandomAccessFile. Seek to the end of the file and then seek and read backwards
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Expert Comment

by:StillUnAware
ID: 16979712
You can use RandomAccessFile from java.io
Using that Object You can open a file and move the file pointer whereever You want using the seek(long l) function.
See:
http://java.sun.com/j2se/1.5.0/docs/api/java/io/RandomAccessFile.html
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Assisted Solution

by:StillUnAware
StillUnAware earned 920 total points
ID: 16979728
It would look something like that:

    RandomAccessFile raf = new RandomAccessFile("filename", "rw");
    byte[] buf = new byte[raf.length() > 10000 ? 10000 : (int)raf.length()];
    raf.seek(raf.length()-buf.length);
    raf.read(buf);
    System.out.println(new String(buf));
    raf.close();
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CEHJ earned 920 total points
ID: 16979775
Here you go

            public static byte[] tail(File f, int length) {
                  RandomAccessFile raf = null;
                  byte[] result = null;
                  try {
                        raf = new RandomAccessFile(f, "r");
                        result = new byte[length];
                        int pointer = (int)f.length();
                        raf.seek(f.length() - length);
                    raf.read(result);
                  }
                  catch(Exception e) {
                    e.printStackTrace();
                  }
                  finally {
                        if (raf != null) {
                              try { raf.close(); } catch(IOException e) { e.printStackTrace(); }
                        }
                  }
                  return result;
            }
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Expert Comment

by:Mayank S
ID: 16981216
Is that somebody's homework done ;-) ?
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Assisted Solution

by:Mayank S
Mayank S earned 160 total points
ID: 16981219
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Expert Comment

by:CEHJ
ID: 16981639
>> Is that somebody's homework done ;-) ?

Wouldn't have thought so - not a very homeworky question ;-)

>>CEHJ, you want to speak on Stringbuffers ;-) ?

Have done ;-)

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Expert Comment

by:Mayank S
ID: 16981691
Thanks :)
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Author Comment

by:piratepatrol
ID: 17006438
You're all so wonderful!  Thank you so much!
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