How to read a locked file as data is inserted?

Question

I have an application that I wrote to mimic the "tail" functionality of unix systems. It runs in a thread, and waits until data is available on an input stream from a file, then it reads from the stream.
This works for some types of file io, but it does NOT work when another process has say, a RandomAccessFile object accessing the file.
My goal is to be able to mimic the tail functionality, even when the file is being written to, but I'm having trouble. I attempted using the NIO FileChannel object to get a channel and then read the bytes in as a buffer, but the only output I'm getting are black boxes, no text. Am I converting the ByteBuffer to a String incorrectly?
Here is the code:
fis = new FileInputStream(file);
fileChannel = fis.getChannel();
int filesize = (int) fileChannel.size();
buf = ByteBuffer.allocate(filesize);
fileChannel.position(pos);
b = new byte[filesize - pos];
fileChannel.read(buf);
fileChannel.close();
pos = filesize;
try {
   buf.get(b);
} catch (BufferUnderflowException ex) {
   //nothing
String contents = new String(b);//.replaceAll("{code}                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

Answer 1

Am I converting the ByteBuffer to a String incorrectly?No.
buf.flip();
buf.get(b);
buf.compact();You always need flip & compact around a get or write operation.