Seems I've sorted it..

 
        ByteBuffer buf = ByteBuffer.allocate(LEN_DATA);
        fc.read(buf, recordOffset + dataOffset);
        buf.position(0);
        byte[] bytearr = new byte[buf.remaining()];
        buf.get(bytearr);
        String strElevation = new String(bytearr);
        return Integer.parseInt(strElevation);
 

Ugh!

Are you forced to use Java language?

'Cus there are JVM languages that'll make that as simple as:

data = readFile(name);
elevation = data[4];

Uh. I'm guessing so, yeah