simpletimezone.java

java源代码 请看看啊 提点宝贵的意见

	// 7-argument getOffset(), and outside code should use Calendar.get(int
	// field) with fields ZONE_OFFSET and DST_OFFSET. We can't get rid of
	// this method because it's public API. - liu 8/10/98
        if (month < Calendar.JANUARY
            || month > Calendar.DECEMBER) {
            throw new IllegalArgumentException("Illegal month " + month);
        }

	int monthLength, prevMonthLength;
	if ((era == GregorianCalendar.AD) && Gregorian.isLeapYear(year)) {
	    monthLength = staticLeapMonthLength[month];
	    prevMonthLength = (month > 1) ? staticLeapMonthLength[month - 1] : 31;
	} else {
	    monthLength = staticMonthLength[month];
	    prevMonthLength = (month > 1) ? staticMonthLength[month - 1] : 31;
	}

	if (true) {
            /* Use this parameter checking code for normal operation.  Only one
             * of these two blocks should actually get compiled into the class
             * file.  */
            if ((era != GregorianCalendar.AD && era != GregorianCalendar.BC)
                || month < Calendar.JANUARY
                || month > Calendar.DECEMBER
                || day < 1
                || day > monthLength
                || dayOfWeek < Calendar.SUNDAY
                || dayOfWeek > Calendar.SATURDAY
                || millis < 0
                || millis >= millisPerDay) {
                throw new IllegalArgumentException();
            }
        } else {
            /* This parameter checking code is better for debugging, but
             * overkill for normal operation.  Only one of these two blocks
             * should actually get compiled into the class file.  */
            if (era != GregorianCalendar.AD && era != GregorianCalendar.BC) {
                throw new IllegalArgumentException("Illegal era " + era);
            }
            if (month < Calendar.JANUARY
                || month > Calendar.DECEMBER) {
                throw new IllegalArgumentException("Illegal month " + month);
            }
            if (day < 1 || day > monthLength) {
                throw new IllegalArgumentException("Illegal day " + day);
            }
            if (dayOfWeek < Calendar.SUNDAY
                || dayOfWeek > Calendar.SATURDAY) {
                throw new IllegalArgumentException("Illegal day of week " + dayOfWeek);
            }
            if (millis < 0 || millis >= millisPerDay) {
                throw new IllegalArgumentException("Illegal millis " + millis);
            }
        }

        return getOffset(era, year, month, day, dayOfWeek, millis,
			 monthLength, prevMonthLength);
    }

    /**
     * Gets offset, for current date, modified in case of
     * daylight saving time. This is the offset to add <em>to</em> UTC to get local time.
     * Gets the time zone offset, for current date, modified in case of daylight
     * saving time. This is the offset to add to UTC to get local time. Assume
     * that the start and end month are distinct.
     * @param era           The era of the given date.
     * @param year          The year in the given date.
     * @param month         The month in the given date. Month is 0-based. e.g.,
     *                      0 for January.
     * @param day           The day-in-month of the given date.
     * @param dayOfWeek     The day-of-week of the given date.
     * @param millis        The milliseconds in day in <em>standard</em> local time.
     * @param monthLength   The length of the given month in days.
     * @param prevMonthLength The length of the previous month in days.
     * @return              The offset to add to GMT to get local time.
     * @exception IllegalArgumentException the era, month, day,
     * dayOfWeek, millis, or monthLength parameters are out of range
     */
    private int getOffset(int era, int year, int month, int day, int dayOfWeek,
			  int millis, int monthLength, int prevMonthLength) {
        int result = rawOffset;

        // Bail out if we are before the onset of daylight saving time
        if (!useDaylight || year < startYear || era != GregorianCalendar.AD) {
	    return result;
	}

        // Check for southern hemisphere.  We assume that the start and end
        // month are different.
        boolean southern = (startMonth > endMonth);

        // Compare the date to the starting and ending rules.+1 = date>rule, -1
        // = date<rule, 0 = date==rule.
        int startCompare = compareToRule(month, monthLength, prevMonthLength,
                                         day, dayOfWeek, millis,
                                         startTimeMode == UTC_TIME ? -rawOffset : 0,
                                         startMode, startMonth, startDayOfWeek,
                                         startDay, startTime);
        int endCompare = 0;

        /* We don't always have to compute endCompare.  For many instances,
         * startCompare is enough to determine if we are in DST or not.  In the
         * northern hemisphere, if we are before the start rule, we can't have
         * DST.  In the southern hemisphere, if we are after the start rule, we
         * must have DST.  This is reflected in the way the next if statement
         * (not the one immediately following) short circuits. */
        if (southern != (startCompare >= 0)) {
            /* For the ending rule comparison, we add the dstSavings to the millis
             * passed in to convert them from standard to wall time.  We then must
             * normalize the millis to the range 0..millisPerDay-1. */
            endCompare = compareToRule(month, monthLength, prevMonthLength,
                                       day, dayOfWeek, millis,
                                       endTimeMode == WALL_TIME ? dstSavings :
                                        (endTimeMode == UTC_TIME ? -rawOffset : 0),
                                       endMode, endMonth, endDayOfWeek,
                                       endDay, endTime);
        }

        // Check for both the northern and southern hemisphere cases.  We
        // assume that in the northern hemisphere, the start rule is before the
        // end rule within the calendar year, and vice versa for the southern
        // hemisphere.
        if ((!southern && (startCompare >= 0 && endCompare < 0)) ||
		(southern && (startCompare >= 0 || endCompare < 0))) {
            result += dstSavings;
	}

        return result;
    }

    /**
     * Compares the given date in the year to the given rule and returns 1, 0,
     * or -1, depending on whether the date is after, equal to, or before the
     * rule date. The millis are compared directly against the ruleMillis, so
     * any standard-daylight adjustments must be handled by the caller.
     *
     * @return  1 if the date is after the rule date, -1 if the date is before
     *          the rule date, or 0 if the date is equal to the rule date.
     */
    private static int compareToRule(int month, int monthLen, int prevMonthLen,
                                     int dayOfMonth,
                                     int dayOfWeek, int millis, int millisDelta,
                                     int ruleMode, int ruleMonth, int ruleDayOfWeek,
                                     int ruleDay, int ruleMillis)
    {
        // Make adjustments for startTimeMode and endTimeMode
        millis += millisDelta;
        while (millis >= millisPerDay) {
            millis -= millisPerDay;
            ++dayOfMonth;
            dayOfWeek = 1 + (dayOfWeek % 7); // dayOfWeek is one-based
            if (dayOfMonth > monthLen) {
                dayOfMonth = 1;
                /* When incrementing the month, it is desirable to overflow
                 * from DECEMBER to DECEMBER+1, since we use the result to
                 * compare against a real month. Wraparound of the value
                 * leads to bug 4173604. */
                ++month;
            }
        }
        while (millis < 0) {
            millis += millisPerDay;
            --dayOfMonth;
            dayOfWeek = 1 + ((dayOfWeek+5) % 7); // dayOfWeek is one-based
            if (dayOfMonth < 1) {
                dayOfMonth = prevMonthLen;
                --month;
            }
        }
        
        if (month < ruleMonth) {
	    return -1;
	}
        if (month > ruleMonth) {
	    return 1;
	}

        int ruleDayOfMonth = 0;
        switch (ruleMode) {
        case DOM_MODE:
            ruleDayOfMonth = ruleDay;
            break;

        case DOW_IN_MONTH_MODE:
            // In this case ruleDay is the day-of-week-in-month
            if (ruleDay > 0) {
                ruleDayOfMonth = 1 + (ruleDay - 1) * 7 +
                    (7 + ruleDayOfWeek - (dayOfWeek - dayOfMonth + 1)) % 7;
            } else {
		// Assume ruleDay < 0 here
                ruleDayOfMonth = monthLen + (ruleDay + 1) * 7 -
                    (7 + (dayOfWeek + monthLen - dayOfMonth) - ruleDayOfWeek) % 7;
            }
            break;

        case DOW_GE_DOM_MODE:
            ruleDayOfMonth = ruleDay +
                (49 + ruleDayOfWeek - ruleDay - dayOfWeek + dayOfMonth) % 7;
            break;

        case DOW_LE_DOM_MODE:
            ruleDayOfMonth = ruleDay -
                (49 - ruleDayOfWeek + ruleDay + dayOfWeek - dayOfMonth) % 7;
            // Note at this point ruleDayOfMonth may be <1, although it will
            // be >=1 for well-formed rules.
            break;
        }

        if (dayOfMonth < ruleDayOfMonth) {
	    return -1;
	}
        if (dayOfMonth > ruleDayOfMonth) {
	    return 1;
	}

        if (millis < ruleMillis) {
	    return -1;
	}
	if (millis > ruleMillis) {
	    return 1;
	}
	return 0;
    }

    /**
     * Gets the GMT offset for this time zone.
     * @return the GMT offset value in milliseconds
     * @see #setRawOffset
     */
    public int getRawOffset()
    {
        // The given date will be taken into account while
        // we have the historical time zone data in place.
        return rawOffset;
    }

    /**
     * Sets the base time zone offset to GMT.
     * This is the offset to add to UTC to get local time.
     * @see #getRawOffset
     */
    public void setRawOffset(int offsetMillis)
    {
        this.rawOffset = offsetMillis;
    }

    /**
     * Sets the amount of time in milliseconds that the clock is advanced
     * during daylight saving time.
     * @param millisSavedDuringDST the number of milliseconds the time is
     * advanced with respect to standard time when the daylight saving time rules
     * are in effect. A positive number, typically one hour (3600000).
     * @see #getDSTSavings
     * @since 1.2
     */
    public void setDSTSavings(int millisSavedDuringDST) {
        if (millisSavedDuringDST <= 0) {
            throw new IllegalArgumentException("Illegal daylight saving value: "
					       + millisSavedDuringDST);
        }
        dstSavings = millisSavedDuringDST;
    }

    /**
     * Returns the amount of time in milliseconds that the clock is
     * advanced during daylight saving time.
     *
     * @return the number of milliseconds the time is advanced with
     * respect to standard time when the daylight saving rules are in
     * effect, or 0 (zero) if this time zone doesn't observe daylight
     * saving time.
     *
     * @see #setDSTSavings
     * @since 1.2
     */
    public int getDSTSavings() {
	if (useDaylight) {
	    return dstSavings;
	}
	return 0;
    }

    /**
     * Queries if this time zone uses daylight saving time.
     * @return true if this time zone uses daylight saving time;
     * false otherwise.
     */
    public boolean useDaylightTime()
    {
        return useDaylight;
    }

    /**
     * Queries if the given date is in daylight saving time.
     * @return true if daylight saving time is in effective at the
     * given date; false otherwise.
     */
    public boolean inDaylightTime(Date date)
    {
	return (getOffset(date.getTime()) != rawOffset);
    }

    /**
     * Returns a clone of this <code>SimpleTimeZone</code> instance.