docs: public MonetaryFormat negativeSign(char negativeSign) {
          checkArgument(!Character.isDigit(negativeSign));
          checkArgument(negativeSign > 0);
          if (negativeSign == this.negativeSign)
              return this;
          else
              return new MonetaryFormat(negativeSign, positiveSign, zeroDigit, decimalMark, minDecimals, decimalGroups,
                      shift, roundingMode, codes, codeSeparator, codePrefixed);
      }