code: @Override
      public void handleWarning(Source source, int line, int column,
              String msg)
              throws LexerException {
          warnings++;
          print(source.getName() + ":" + line + ":" + column
                  + ": warning: " + msg);
      }
docs: Handles a warning.
  
  The behaviour of this method is defined by the
  implementation. It may simply record the error message, or
  it may throw an exception.