docs: public User findUser(final String userIdentifier)
      {
          User result = null;
          User user;
          
          for(int i = 0; (result == null) && (i < this.getUsers().size()); i++)
          {
              user = this.getUsers().get(i);
              
              if(user.getIdentifier().equals(userIdentifier))
              {
                  result = user;
              }
          }
          
          return result;
      }