code: String messageFormat(String key, Object... args) {
          if (outputRB == null) {
              try {
                  outputRB = ResourceBundle.getBundle(L10N_RB_NAME);
              } catch (MissingResourceException mre) {
                  throw new InternalError("Cannot find ResourceBundle: " + L10N_RB_NAME);
              }
          }
          String s;
          try {
              s = outputRB.getString(key);
          } catch (MissingResourceException mre) {
              throw new InternalError("Missing resource: " + key + " in " + L10N_RB_NAME);
          }
          return MessageFormat.format(s, args);
      }
docs: Format using resource bundle look-up using MessageFormat
  
  @param key the resource key
  @param args