code: public int[] fractionPlaceGroups() {
          Object[] boxedArray = decimalGroups.toArray();
          int len = boxedArray.length + 1;
          int[] array = new int[len];
          array[0] = minimumFractionDigits;
          for (int i = 1; i < len; i++) { array[i] = (Integer) boxedArray[i-1]; }
          return array;
      }
docs: Return the fractional decimal-placing used when formatting.  This method returns an
  {@code int} array.  The value of the first element is the minimum number of
  decimal places to be used in all cases, limited to a precision of satoshis.  The value
  of each successive element is the size of an optional place-group that will be applied,
  possibly partially, if useful for expressing precision.  The actual size of each group
  is limited to, and may be reduced to the limit of, a precision of no smaller than
  satoshis.