code: public static Optional<String> at(final String value, int index) {
          if (isNullOrEmpty(value)) {
              return Optional.empty();
          }
          int length = value.length();
          if (index < 0) {
              index = length + index;
          }
          return (index < length && index >= 0) ? Optional.of(String.valueOf(value.charAt(index))) : Optional.empty();
      }
docs: Get the character at index. This method will take care of negative indexes.
  The valid value of index is between -(length-1) to (length-1).
  For values which don't fall under this range Optional.empty will be returned.
  
  @param value input value
  @param index location
  @return an Optional String if found else empty