simpletimezone.java

来自「《移动Agent技术》一书的所有章节源代码。」· Java 代码 · 共 739 行 · 第 1/3 页

        // Bail out if we are before the onset of daylight savings 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.  For the ending
        // rule comparison, we add the dstSavings to the millis passed in to convert
        // them from standard to wall time.  +1 = date>rule, -1 = date<rule, 0 =
        // date==rule.
        int startCompare = compareToRule(month, day, dayOfWeek, millis,
                                         startMode, startMonth, startDayOfWeek,
                                         startDay, startTime);
        int endCompare = compareToRule(month, day, dayOfWeek, millis + dstSavings,
                                       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;
    }

    /**
     * Compare a given date in the year to a rule. Return 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. Assume that
     * no rule references the end of February (e.g., last Sunday in February).
     *
     * @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 dayOfMonth, int dayOfWeek, int millis,
                                     int ruleMode, int ruleMonth, int ruleDayOfWeek,
                                     int ruleDay, int ruleMillis)
    {
        if (month < ruleMonth) return -1;
        else 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
            {
                int monthLen = staticMonthLength[month];

                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;
        else if (dayOfMonth > ruleDayOfMonth) return 1;

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

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

    /**
     * Overrides TimeZone
     * Sets the base time zone offset to GMT.
     * This is the offset to add *to* UTC to get local time.
     * Please see TimeZone.setRawOffset for descriptions on the parameter.
     */
    public void setRawOffset(int offsetMillis)
    {
        this.rawOffset = offsetMillis;
    }

    /**
     * Overrides TimeZone
     * Queries if this time zone uses Daylight Savings Time.
     */
    public boolean useDaylightTime()
    {
        return useDaylight;
    }

    /**
     * Overrides TimeZone
     * Queries if the given date is in Daylight Savings Time.
     */
    public boolean inDaylightTime(Date date)
    {
        GregorianCalendar gc = new GregorianCalendar(this);
        gc.setTime(date);
        return gc.inDaylightTime();
    }

    /**
     * Overrides Cloneable
     */
    public Object clone()
    {
        return super.clone();
        // other fields are bit-copied
    }

    /**
     * Override hashCode.
     * Generates the hash code for the SimpleDateFormat object
     */
    public synchronized int hashCode()
    {
        return startMonth ^ startDay ^ startDayOfWeek ^ startTime ^
            endMonth ^ endDay ^ endDayOfWeek ^ endTime ^ rawOffset;
    }

    /**
     * Compares the equality of two SimpleTimeZone objects.
     *
     * @param obj  The SimpleTimeZone object to be compared with.
     * @return     True if the given obj is the same as this SimpleTimeZone
     *             object; false otherwise.
     */
    public boolean equals(Object obj)
    {
        if (this == obj)
            return true;
        if (!(obj instanceof SimpleTimeZone))
            return false;

        SimpleTimeZone that = (SimpleTimeZone) obj;

        return this.getID().equals(that.getID()) &&
            rawOffset == that.rawOffset &&
            useDaylight == that.useDaylight &&
            dstSavings == that.dstSavings &&
            startMode == that.startMode &&
            startMonth == that.startMonth &&
            startDay == that.startDay &&
            startDayOfWeek == that.startDayOfWeek &&
            startTime == that.startTime &&
            endMode == that.endMode &&
            endMonth == that.endMonth &&
            endDay == that.endDay &&
            endDayOfWeek == that.endDayOfWeek &&
            endTime == that.endTime &&
            startYear == that.startYear;
    }

    /**
     * Return a string representation of this time zone.
     * @return  a string representation of this time zone.
     */
    public String toString() {
        return getClass().getName() +
            "[id=" + getID() +
            ",offset=" + rawOffset +
            ",dstSavings=" + dstSavings +
            ",useDaylight=" + useDaylight +
            ",startYear=" + startYear +
            ",startMode=" + startMode +
            ",startMonth=" + startMonth +
            ",startDay=" + startDay +
            ",startDayOfWeek=" + startDayOfWeek +
            ",startTime=" + startTime +
            ",endMode=" + endMode +
            ",endMonth=" + endMonth +
            ",endDay=" + endDay +
            ",endDayOfWeek=" + endDayOfWeek +
            ",endTime=" + endTime + ']';
    }

    // =======================privates===============================

    private int startMonth, startDay, startDayOfWeek, startTime;
    private int endMonth, endDay, endDayOfWeek, endTime;
    private int startYear;
    private int rawOffset;
    private boolean useDaylight=false; // indicate if this time zone uses DST
    private static final int millisPerHour = 60*60*1000;
    // WARNING: assumes that no rule is measured from the end of February,
    // since we don't handle leap years. Could handle assuming always
    // Gregorian, since we know they didn't have daylight time when
    // Gregorian calendar started.
    // monthLength was non-static in JDK 1.1, so we have to keep it that way
    // to maintain serialization compatibility. However, there's no need to
    // recreate the array each time we create a new time zone.
    private final byte monthLength[] = staticMonthLength;
    private final static byte staticMonthLength[] = {31,28,31,30,31,30,31,31,30,31,30,31};

    /** 
     * Variables specifying the mode of the start and end rules.
     */
    private int startMode, endMode; // fields new in JDK 1.1.4

    /**
     * A positive value indicating the amount of time saved during DST in ms.
     * Typically one hour; sometimes 30 minutes.
     */
    private int dstSavings; // field new in JDK 1.1.4

    /** 
     * Constants specifying values of startMode and endMode.
     */
    private static final int DOM_MODE          = 1; // Exact day of month, "Mar 1"
    private static final int DOW_IN_MONTH_MODE = 2; // Day of week in month, "lastSun"
    private static final int DOW_GE_DOM_MODE   = 3; // Day of week after day of month, "Sun>=15"
    private static final int DOW_LE_DOM_MODE   = 4; // Day of week before day of month, "Sun<=21"

    // Proclaim compatibility with 1.1
    static final long serialVersionUID = -403250971215465050L;

    // the internal serial version which says which version was written
    // - 0 (default) for version up to JDK 1.1.3
    // - 1 for version from JDK 1.1.4, which includes 3 new fields
    static final int currentSerialVersion = 1;