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