public XmlDom child(String tag,String attr,String value){
  List<XmlDom> c=children(tag,attr,value);
  if (c.size() == 0)   return null;
  return c.get(0);
}

public XmlDom child ( String tag , String attr , String value ) { List < XmlDom > c = children ( tag , attr , value ) ; if ( c . size ( ) == 0 ) return null ; return c . get ( 0 ) ; }
return the first child node that represent the matched tag that has attribute attr = value . a dummy node is returned if none found .
