code: public static String numericOffset(String initial, String offset) {
          BigDecimal number;
          BigDecimal dOffset;
  
          try {
              number = new BigDecimal(initial);
              dOffset = new BigDecimal(offset);
          } catch (Exception ex) {
              return null;
          }
          return number.add(dOffset).toString();
      }
docs: Offset a numeric string by another numeric string.
  
  Any numeric string recognized by {@code BigDecimal} is supported.
  
  @param initial A valid number string
  @param offset A valid number string
  
  @return a number string with the precision matching the highest precision
  argument.
  
  @see BigDecimal