Periodically incrementally reading text file as byte array ignoring partially appended lines

Question

I am trying to read into byte array a text file which is appended by another process. I'd like to "poll" the file periodically to extract only new "full" lines of text (the lines ended with a new line). What's the best way to do this in Java 6 using standard libraries?

I am not interested in storing and creating Strings, so probably all the "readLine()" methods from readers are not the ones I should look into. I am thinking of using RandomAccessFile, but I am wondering how to truncate the read byte array so it would end at the last new line character.

Peter Lawrey · Accepted Answer · 2012-06-12 07:08:39Z

1

You can have one thread which polls the file's length. When the length increases, read that length as a byte[] (and no more, so don't use BufferedInputStream) and you will be able to continue reading the file later. Take the byte[] and write it to a PipedOutputStream.

In your main thread you can use BufferedReader + InputStreamReader + PipedInputStream. Using that a plain readLine() will do fine.

answered Jun 12, 2012 at 7:08

Peter Lawrey

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