code: public String readLine() throws IOException {
          synchronized (lock) {
              String l = super.readLine(skipLF);
              skipLF = false;
              if (l != null)
                  lineNumber++;
              return l;
          }
      }
docs: Read a line of text.  Whenever a <a href="#lt">line terminator</a> is
  read the current line number is incremented.
  
  @return  A String containing the contents of the line, not including
  any <a href="#lt">line termination characters</a>, or
  <tt>null</tt> if the end of the stream has been reached
  
  @throws  IOException
  If an I/O error occurs