code: public static BasicPeriodFormatterService getInstance() {
          if (instance == null) {
              PeriodFormatterDataService ds = ResourceBasedPeriodFormatterDataService
                      .getInstance();
              instance = new BasicPeriodFormatterService(ds);
          }
          return instance;
      }
docs: Return the default service instance. This uses the default data service.
  
  @return an BasicPeriodFormatterService