code: public static long parseCacheControlSeconds(@Nullable String value) {
          if (value == null) {
              return -1;
          }
  
          try {
              final long converted = Long.parseLong(value);
              return converted >= 0 ? converted : -1;
          } catch (NumberFormatException e) {
              return -1;
          }
      }
docs: Converts the specified {@code "cache-control"} directive value into a long integer.
  
  @return the converted value if {@code value} is equal to or greater than {@code 0}.
  {@code -1} otherwise, i.e. if a negative integer or not a number.