if (!isName(dtd)) throw new IllegalArgumentException("illegal Name: " + dtd);
  public void writeDTD(String dtd)    throws XMLStreamException  {    try      {        writer.write("<!DOCTYPE ");        writer.write(dtd);        writer.write('>');      }    catch (IOException e)      {        XMLStreamException e2 = new XMLStreamException(e);        e2.initCause(e);        throw e2;      }  }