/**
   * Method addUserToParticipantList.
   *
   * @param aUser - String
   */
  private void addUsersToParticipantList(String aUser) {
    // Here we first need to resolve any group aliases to multiple users
    final List<String> resolvedUsers = R4EPreferencePage.getParticipantsFromList(aUser.trim());

    for (String user : resolvedUsers) {
      String[] userTokens = user.split(R4EUIConstants.LIST_SEPARATOR);

      // Resolve user in database (if possible)
      R4EParticipant participant = getParticipant(userTokens[0].toLowerCase());
      if (null == participant) {
        return; // Participant already in list
      }

      // Override email with address defined in users group (if any)
      if (2 == userTokens.length && !(userTokens[1].trim().equals(""))) {
        participant.setEmail(userTokens[1]);
      }

      // Override email with address defined in current review (if any)
      if (null != R4EUIModelController.getActiveReview()) {
        R4EParticipant reviewParticipant;
        try {
          reviewParticipant =
              R4EUIModelController.getActiveReview().getParticipant(participant.getId(), false);
          if (null != reviewParticipant) {
            participant.setEmail(reviewParticipant.getEmail());
          }
        } catch (ResourceHandlingException e) {
          UIUtils.displayResourceErrorDialog(e);
        }
      }
      fParticipants.add(participant);
      updateComponents(participant);
    }
  }