default B withDefault(Field field,Class<?> value){
  return withDefault(field.name(),value != null ? value.getName() : null);
}

default B withDefault ( Field field , Class < ? > value ) { return withDefault ( field . name ( ) , value != null ? value . getName ( ) : null ) ; }
if the field does not have a value , then associate the given value with the key of the specified field .
