code: static Integer numerator(final String s) {
          if ("".equals(s)) {
              return null;
          }
          String[] tokens = s.split("/");
          return emptyToNullInteger(tokens[0]);
      }
docs: Parse the specified string as a fraction and return the numerator, if any.
  
  @param s string to parse
  @return the numerator from the specified string parsed as a fraction, or null if the string is empty