public MonetaryFormat decimalMark(char decimalMark) {
        checkArgument(!Character.isDigit(decimalMark), () ->
                "decimalMark can't be digit: " + decimalMark);
        checkArgument(decimalMark > 0, () ->
                "decimalMark must be positive: " + decimalMark);
        if (decimalMark == this.decimalMark)
            return this;
        else
            return new MonetaryFormat(negativeSign, positiveSign, zeroDigit, decimalMark, minDecimals, decimalGroups,
                    shift, roundingMode, codes, codeSeparator, codePrefixed);
    }
@Test
    public void testDecimalMark() {
        assertEquals("1.00", NO_CODE.format(Coin.COIN).toString());
        assertEquals("1,00", NO_CODE.decimalMark(',').format(Coin.COIN).toString());
    }