Method parseAlt

base/src/main/java/net/time4j/Duration.java:3629–3723

(
        String period,
        int from,
        int to,
        boolean date,
        List<Item<U>> items
    )

    }

    private static <U extends ChronoUnit> void parseAlt(
        String period,
        int from,
        int to,
        boolean date,
        List<Item<U>> items
    ) throws ParseException {

        boolean extended = false;

        if (date) {
            if (from + 4 < to) {
                extended = (period.charAt(from + 4) == '-');
            }
            boolean ordinalStyle = (
                extended
                ? (from + 8 == to)
                : (from + 7 == to));
            Duration<?> dur = getAlternativeDateFormat(extended, ordinalStyle).parse(period, from);
            long years = dur.getPartialAmount(YEARS);
            long months;
            long days;
            if (ordinalStyle) {
                months = 0;
                days = dur.getPartialAmount(DAYS);
                // ISO does not specify any constraint here
            } else {
                months = dur.getPartialAmount(MONTHS);
                days = dur.getPartialAmount(DAYS);
                if (months > 12) {
                    throw new ParseException(
                        "ISO-8601 prohibits months-part > 12: " + period,
                        from + 4 + (extended ? 1 : 0));
                }
                if (days > 30) {
                    throw new ParseException(
                        "ISO-8601 prohibits days-part > 30: " + period,
                        from + 6 + (extended ? 2 : 0));
                }
            }
            if (years > 0) {
                U unit = cast(YEARS);
                items.add(Item.of(years, unit));
            }
            if (months > 0) {
                U unit = cast(MONTHS);
                items.add(Item.of(months, unit));
            }
            if (days > 0) {
                U unit = cast(DAYS);
                items.add(Item.of(days, unit));
            }
        } else {
            if (from + 2 < to) {
                extended = (period.charAt(from + 2) == ':');
            }
            Duration<?> dur = getAlternativeTimeFormat(extended).parse(period, from);
            long hours = dur.getPartialAmount(HOURS);