code: public static BtcFormat getInstance(int scale, Locale locale, int minDecimals, List<Integer> groups) {
          return new BtcFixedFormat(locale, scale, minDecimals, groups);
      }
docs: Return a new fixed-denomination formatter for the given locale, with the specified
  fractional decimal placing.  The first argument specifies the denomination as the size
  of the shift from coin-denomination in increasingly-precise decimal places.  The third
  parameter is the minimum number of fractional decimal places to use.  The third argument
  specifies the minimum number of fractional decimal places in formatted numbers.  The
  last argument is a {@code List} of {@link Integer} values, each of which
  specifies the size of an additional group of fractional decimal places to use as
  necessary to avoid rounding, down to a maximum precision of satoshis.