code: private Principal selectedPrincipal() {
          if (browseByColumn.getSelectedItem().getTitle().equals(Console.CONSTANTS.common_label_users())) {
              return userColumn.getSelectedItem();
          } else if (browseByColumn.getSelectedItem().getTitle().equals(Console.CONSTANTS.common_label_groups())) {
              return groupColumn.getSelectedItem();
          }
          return null;
      }
docs: ------------------------------------------------------ helper methods