public static <E> StringInstantId<E> of(Class<E> type, String id) {

    return of(type, id, null);
  }
public static < E > StringInstantId < E > of ( Class < E > type , String id ) { return of ( type , id , null ) ; }
@param <E> the generic type of the identified entity.
@param type the {@link #getType() type}.
@param id the {@link #getId() primary key}.
@return the new {@link StringInstantId} or {@code null} if the given {@code id} was {@code null}.