public void addError(Element element,ErrorContent error){
  List<ErrorContent> list=errors.get(element);
  if (list == null) {
    list=Lists.newArrayList();
    errors.put(element,list);
  }
  list.add(error);
}

public void addError ( Element element , ErrorContent error ) { List < ErrorContent > list = errors . get ( element ) ; if ( list == null ) { list = Lists . newArrayList ( ) ; errors . put ( element , list ) ; } list . add ( error ) ; }
add a validation error to list .
