code: public static RelativeDateTimeFormatter getInstance(ULocale locale, NumberFormat nf) {
          return getInstance(locale, nf, Style.LONG, DisplayContext.CAPITALIZATION_NONE);
      }
docs: Returns a RelativeDateTimeFormatter for a particular locale that uses a particular
  NumberFormat object.
  
  @param locale the locale
  @param nf the number format object. It is defensively copied to ensure thread-safety
  and immutability of this class.
  @return An instance of RelativeDateTimeFormatter.