public static String formatPeriod()

in src/main/java/org/apache/commons/lang3/time/DurationFormatUtils.java [529:658]
94 lines of code
23 McCabe index (conditional complexity)

    public static String formatPeriod(final long startMillis, final long endMillis, final String format, final boolean padWithZeros,
            final TimeZone timezone) {
        Validate.isTrue(startMillis <= endMillis, "startMillis must not be greater than endMillis");

        // Used to optimize for differences under 28 days and
        // called formatDuration(millis, format); however this did not work
        // over leap years.
        // TODO: Compare performance to see if anything was lost by
        // losing this optimization.

        final Token[] tokens = lexx(format);

        // time zones get funky around 0, so normalizing everything to GMT
        // stops the hours being off
        final Calendar start = Calendar.getInstance(timezone);
        start.setTime(new Date(startMillis));
        final Calendar end = Calendar.getInstance(timezone);
        end.setTime(new Date(endMillis));

        // initial estimates
        long milliseconds = end.get(Calendar.MILLISECOND) - start.get(Calendar.MILLISECOND);
        int seconds = end.get(Calendar.SECOND) - start.get(Calendar.SECOND);
        int minutes = end.get(Calendar.MINUTE) - start.get(Calendar.MINUTE);
        int hours = end.get(Calendar.HOUR_OF_DAY) - start.get(Calendar.HOUR_OF_DAY);
        int days = end.get(Calendar.DAY_OF_MONTH) - start.get(Calendar.DAY_OF_MONTH);
        int months = end.get(Calendar.MONTH) - start.get(Calendar.MONTH);
        int years = end.get(Calendar.YEAR) - start.get(Calendar.YEAR);

        // each initial estimate is adjusted in case it is under 0
        while (milliseconds < 0) {
            milliseconds += DateUtils.MILLIS_PER_SECOND;
            seconds -= 1;
        }
        while (seconds < 0) {
            seconds += SECONDS_PER_MINUTES;
            minutes -= 1;
        }
        while (minutes < 0) {
            minutes += MINUTES_PER_HOUR;
            hours -= 1;
        }
        while (hours < 0) {
            hours += HOURS_PER_DAY;
            days -= 1;
        }

        if (Token.containsTokenWithValue(tokens, M)) {
            while (days < 0) {
                days += start.getActualMaximum(Calendar.DAY_OF_MONTH);
                months -= 1;
                start.add(Calendar.MONTH, 1);
            }

            while (months < 0) {
                months += 12;
                years -= 1;
            }

            if (!Token.containsTokenWithValue(tokens, y) && years != 0) {
                while (years != 0) {
                    months += 12 * years;
                    years = 0;
                }
            }
        } else {
            // there are no M's in the format string

            if (!Token.containsTokenWithValue(tokens, y)) {
                int target = end.get(Calendar.YEAR);
                if (months < 0) {
                    // target is end-year -1
                    target -= 1;
                }

                while (start.get(Calendar.YEAR) != target) {
                    days += start.getActualMaximum(Calendar.DAY_OF_YEAR) - start.get(Calendar.DAY_OF_YEAR);

                    // Not sure I grok why this is needed, but the brutal tests show it is
                    if (start instanceof GregorianCalendar &&
                            start.get(Calendar.MONTH) == Calendar.FEBRUARY &&
                            start.get(Calendar.DAY_OF_MONTH) == 29) {
                        days += 1;
                    }

                    start.add(Calendar.YEAR, 1);

                    days += start.get(Calendar.DAY_OF_YEAR);
                }

                years = 0;
            }

            while (start.get(Calendar.MONTH) != end.get(Calendar.MONTH)) {
                days += start.getActualMaximum(Calendar.DAY_OF_MONTH);
                start.add(Calendar.MONTH, 1);
            }

            months = 0;

            while (days < 0) {
                days += start.getActualMaximum(Calendar.DAY_OF_MONTH);
                months -= 1;
                start.add(Calendar.MONTH, 1);
            }

        }

        // The rest of this code adds in values that
        // aren't requested. This allows the user to ask for the
        // number of months and get the real count and not just 0->11.

        if (!Token.containsTokenWithValue(tokens, d)) {
            hours += HOURS_PER_DAY * days;
            days = 0;
        }
        if (!Token.containsTokenWithValue(tokens, H)) {
            minutes += MINUTES_PER_HOUR * hours;
            hours = 0;
        }
        if (!Token.containsTokenWithValue(tokens, m)) {
            seconds += SECONDS_PER_MINUTES * minutes;
            minutes = 0;
        }
        if (!Token.containsTokenWithValue(tokens, s)) {
            milliseconds += DateUtils.MILLIS_PER_SECOND * seconds;
            seconds = 0;
        }

        return format(tokens, years, months, days, hours, minutes, seconds, milliseconds, padWithZeros);
    }