docs: public void peekExpect(final char expectedChar) throws ParseException {
          if (position == string.length()) {
              throw new ParseException(this, "Expected '" + expectedChar + "'; reached end of string");
          }
          final char next = string.charAt(position);
          if (next != expectedChar) {
              throw new ParseException(this, "Expected '" + expectedChar + "'; got '" + next + "'");
          }
      }