code: public boolean hasUser(String userName) {
          boolean result = false;
          for (User item : getUsersList()) {
              if (item.getName().equals(userName)) {
                  result = true;
              }
          }
          return result;
      }
docs: Check to see if a given user name is within
  the list of users.
  Checking will be done case sensitive.
  @param userName The name of the user which should be checked for.
  @return true if the user has been found false otherwise.