code: @Override
      public StringBuffer format(BigInteger number,
                                 StringBuffer toAppendTo,
                                 FieldPosition pos) {
          return format(new android.icu.math.BigDecimal(number), toAppendTo, pos);
      }
docs: <strong style="font-family: helvetica; color: red;">NEW</strong>
  Implement android.icu.text.NumberFormat:
  Format a BigInteger.