code: public DecimalStyle withZeroDigit(char zeroDigit) {
          if (zeroDigit == this.zeroDigit) {
              return this;
          }
          return new DecimalStyle(zeroDigit, positiveSign, negativeSign, decimalSeparator);
      }
docs: Returns a copy of the info with a new character that represents zero.
  <p>
  The character used to represent digits may vary by culture.
  This method specifies the zero character to use, which implies the characters for one to nine.
  
  @param zeroDigit  the character for zero
  @return  a copy with a new character that represents zero, not null