code: public static BtcFormat getCoinInstance(int minFractionPlaces, int... groups) {
          return getInstance(COIN_SCALE, defaultLocale(), minFractionPlaces, boxAsList(groups));
      }
docs: Return a new coin-denominated formatter with the specified fraction-places.  The
  returned object will format and parse values according to the default locale, and will
  format the fraction part of numbers with at least two decimal places.  The sizes of
  additional groups of decimal places can be specified by a variable number of
  {@code int} arguments.  Each optional decimal-place group will be applied only if
  useful for expressing precision, and will be only partially applied if necessary to
  avoid giving a place to fractional satoshis.