code: private static String getUsername(String url) {
          int atIndex = url.lastIndexOf(USERNAME_INDICATOR);
          if (atIndex < 0) {
              return null;
          }
          String username = url.substring(0, atIndex + 1);
          int slashIndex = username.lastIndexOf('/');
          if (slashIndex > 0) {
              username = username.substring(slashIndex + 1);
          }
          return username;
      }
docs: Returns a String with username.
  '@' character or whatever indicator of it being username is included in the returned value
  
  @param url url to extract username from
  @return username if username is specified in the url, null otherwise