code: private void updateStateAndNotify() {
          Boolean oldGroupValid = groupValid;
          groupValid = true;
          for (Boolean valid : fields.values()) {
              groupValid &= valid;
          }
          if (groupValid != oldGroupValid) {
              eventBus.fireEvent(new ValidationChangedEvent(groupValid));
          }
      }
docs: Update the state of the validator and notify via {@link EventBus} any changed handlers.