calendar.java

来自「《移动Agent技术》一书的所有章节源代码。」· Java 代码 · 共 1,118 行 · 第 1/3 页

    public final static int AM = 0;
    /**
     * Useful constant for hour in 12-hour clock. Used in GregorianCalendar.
     */
    public final static int PM = 1;

    // Internal notes:
    // Calendar contains two kinds of time representations: current "time" in
    // milliseconds, and a set of time "fields" representing the current time.
    // The two representations are usually in sync, but can get out of sync
    // as follows.
    // 1. Initially, no fields are set, and the time is invalid.
    // 2. If the time is set, all fields are computed and in sync.
    // 3. If a single field is set, the time is invalid.
    // Recomputation of the time and fields happens when the object needs
    // to return a result to the user, or use a result for a computation.

    /**
     * The time fields containing values into which the millis is computed.
     */
    protected int           fields[]; // NOTE: Make transient when possible

    /**
     * The flags which tell if a specified time field for the calendar is set.
     * A new object has no fields set.  After the first call to a method
     * which generates the fields, they all remain set after that.
     */
    protected boolean       isSet[]; // NOTE: Remove when possible

    /**
     * Pseudo-time-stamps which specify when each field was set. There
     * are two special values, UNSET and INTERNALLY_SET. Values from
     * MINIMUM_USER_SET to Integer.MAX_VALUE are legal user set values.
     */
    transient int           stamp[];

    /**
     * The current time set for the calendar.
     */
    protected long          time;

    /**
     * The flag which indicates if the current time is set for the calendar.
     * The time is made invalid by the user setting an individual field.
     */
    protected boolean       isTimeSet; // NOTE: Make transient when possible

    /**
     * True if the fields are in sync with the currently set time of this Calendar.
     * If false, then the next attempt to get the value of a field will
     * force a recomputation of all fields from the current value of the time
     * field.
     *
     * This should really be named areFieldsInSync, but the old name is retained
     * for backward compatibility.
     */
    protected boolean       areFieldsSet; // NOTE: Make transient when possible

    /**
     * True if all fields have been set.
     *
     * NOTE: MAKE PROTECTED AT NEXT API CHANGE, or ADD ACCESSOR METHODS.
     */
    transient boolean       areAllFieldsSet;

    /**
     * @see #setLenient
     */
    private boolean         lenient = true;

    /**
     * Time zone affects the time calculation done by Calendar. Calendar uses
     * the time zone data to produce the local time. Both firstDayOfWeek
     * and minimalDaysInFirstWeek are locale-dependent. For example,
     * in US locale, firstDayOfWeek is SUNDAY; minimalDaysInFirstWeek is 1.
     * They are used to figure out the week count for a specific date for
     * a given locale. These must be set when a Calendar is constructed.
     */
    private TimeZone        zone;
    private int             firstDayOfWeek;
    private int             minimalDaysInFirstWeek;

    /**
     * Cache to hold the firstDayOfWeek and minimalDaysInFirstWeek
     * of a Locale.
     */
    private static Hashtable cachedLocaleData = new Hashtable(3);

    // Special values of stamp[]
    static final int        UNSET = 0;
    static final int        INTERNALLY_SET = 1;
    static final int        MINIMUM_USER_STAMP = 2;

    // The next available value for stampp[]
    private int             nextStamp = MINIMUM_USER_STAMP;

    // the internal serial version which says which version was written
    // - 0 (default) for version up to JDK 1.1.5
    // - 1 for version from JDK 1.1.6, which writes a correct 'time' value
    //     as well as compatible values for other fields.  This is a
    //     transitional format.
    // - 2 (not implemented yet) a future version, in which fields[],
    //     areFieldsSet, and isTimeSet become transient, and isSet[] is
    //     removed. In JDK 1.1.6 we write a format compatible with version 2.
    static final int        currentSerialVersion = 1;
    private int             serialVersionOnStream = currentSerialVersion;

    // Proclaim serialization compatibility with JDK 1.1
    static final long       serialVersionUID = -1807547505821590642L;

    /**
     * Constructs a Calendar with the default time zone as returned
     * by TimeZone.getDefault(), and the default locale.
     * @see     TimeZone#getDefault
     */
    protected Calendar()
    {
        this(TimeZone.getDefault(), Locale.getDefault());
    }

    /**
     * Constructs a Calendar with the given time zone and locale.
     * @param zone the given time zone.
     */
    protected Calendar(TimeZone zone, Locale aLocale)
    {
        fields = new int[FIELD_COUNT];
        isSet = new boolean[FIELD_COUNT];
        stamp = new int[FIELD_COUNT];

        this.zone = zone;
        setWeekCountData(aLocale);
    }

    /**
     * Gets a Calendar using the default timezone and locale.
     * @return a Calendar.
     */
    public static synchronized Calendar getInstance()
    {
        return new GregorianCalendar();
    }

    /**
     * Gets a Calendar using the given timezone and default locale.
     * @param zone the given timezone.
     * @return a Calendar.
     */
    public static synchronized Calendar getInstance(TimeZone zone)
    {
        return new GregorianCalendar(zone, Locale.getDefault());
    }

    /**
     * Gets a Calendar using the default timezone and given locale.
     * @param aLocale the given locale.
     * @return a Calendar.
     */
    public static synchronized Calendar getInstance(Locale aLocale)
    {
        return new GregorianCalendar(TimeZone.getDefault(), aLocale);
    }

    /**
     * Gets a Calendar using the given timezone and given locale.
     * @param zone the given timezone.
     * @param aLocale the given locale.
     * @return a Calendar.
     */
    public static synchronized Calendar getInstance(TimeZone zone,
                                                    Locale aLocale)
    {
        return new GregorianCalendar(zone, aLocale);
    }

    /**
     * Gets the set of locales for which Calendars are installed.
     * @return the set of locales for which Calendars are installed.
     */
    public static synchronized Locale[] getAvailableLocales()
    {
        return DateFormat.getAvailableLocales();
    }

    /**
     * Converts Calendar's time field values to UTC as milliseconds.
     */
    protected abstract void computeTime();

    /**
     * Converts UTC as milliseconds to time field values.
     * This allows you to sync up the time field values with
     * a new time that is set for the calendar.  The time is <em>not</em>
     * recomputed first; to recompute the time, then the fields, call the
     * <code>complete</code> method.
     * @see #complete
     */
    protected abstract void computeFields();

    /**
     * Gets this Calendar's current time.
     * @return the current time.
     */
    public final Date getTime() {
        return new Date( getTimeInMillis() );
    }

    /**
     * Sets this Calendar's current time with the given Date.
     * @param date the given Date.
     */
    public final void setTime(Date date) {
        setTimeInMillis( date.getTime() );
    }

    /**
     * Gets this Calendar's current time as a long.
     * @return the current time as UTC milliseconds from the epoch.
     */
    protected long getTimeInMillis() {
        if (!isTimeSet) updateTime();
        return time;
    }

    /**
     * Sets this Calendar's current time from the given long value.
     * @param date the new time in UTC milliseconds from the epoch.
     */
    protected void setTimeInMillis( long millis ) {
        isTimeSet = true;
        time = millis;
        areFieldsSet = false;
        if (!areFieldsSet) {
            computeFields();
            areFieldsSet = true;
            areAllFieldsSet = true;
        }
    }

    /**
     * Gets the value for a given time field.
     * @param field the given time field.
     * @return the value for the given time field.
     */
    public final int get(int field)
    {
        complete();
        return fields[field];
    }

    /**
     * Gets the value for a given time field. This is an internal
     * fast time field value getter for the subclasses.
     * @param field the given time field.
     * @return the value for the given time field.
     */
    protected final int internalGet(int field)
    {
        return fields[field];
    }

    /**
     * Sets the value for the given time field.  This is an internal
     * fast setter for subclasses.  It does not affect the areFieldsSet, isTimeSet,
     * or areAllFieldsSet flags.
     */
    final void internalSet(int field, int value)
    {
        fields[field] = value;
    }

    /**
     * Sets the time field with the given value.
     * @param field the given time field.
     * @param value the value to be set for the given time field.
     */
    public final void set(int field, int value)
    {
        isTimeSet = false;
        fields[field] = value;
        stamp[field] = nextStamp++;
        areFieldsSet = false;
        isSet[field] = true; // Remove later
    }

    /**
     * Sets the values for the fields year, month, and date.
     * Previous values of other fields are retained.  If this is not desired,
     * call <code>clear</code> first.
     * @param year the value used to set the YEAR time field.
     * @param month the value used to set the MONTH time field.
     * Month value is 0-based. e.g., 0 for January.
     * @param date the value used to set the DATE time field.
     */
    public final void set(int year, int month, int date)
    {
        set(YEAR, year);
        set(MONTH, month);
        set(DATE, date);
    }

    /**
     * Sets the values for the fields year, month, date, hour, and minute.
     * Previous values of other fields are retained.  If this is not desired,
     * call <code>clear</code> first.
     * @param year the value used to set the YEAR time field.
     * @param month the value used to set the MONTH time field.
     * Month value is 0-based. e.g., 0 for January.
     * @param date the value used to set the DATE time field.
     * @param hour the value used to set the HOUR_OF_DAY time field.
     * @param minute the value used to set the MINUTE time field.
     */
    public final void set(int year, int month, int date, int hour, int minute)
    {
        set(YEAR, year);
        set(MONTH, month);
        set(DATE, date);
        set(HOUR_OF_DAY, hour);
        set(MINUTE, minute);
    }

    /**
     * Sets the values for the fields year, month, date, hour, minute, and second.
     * Previous values of other fields are retained.  If this is not desired,
     * call <code>clear</code> first.
     * @param year the value used to set the YEAR time field.
     * @param month the value used to set the MONTH time field.
     * Month value is 0-based. e.g., 0 for January.
     * @param date the value used to set the DATE time field.
     * @param hour the value used to set the HOUR_OF_DAY time field.
     * @param minute the value used to set the MINUTE time field.
     * @param second the value used to set the SECOND time field.
     */
    public final void set(int year, int month, int date, int hour, int minute,
                          int second)
    {
        set(YEAR, year);
        set(MONTH, month);
        set(DATE, date);
        set(HOUR_OF_DAY, hour);
        set(MINUTE, minute);
        set(SECOND, second);
    }

    /**
     * Clears the values of all the time fields.
     */
    public final void clear()
    {
        fields = new int[FIELD_COUNT];
        stamp = new int[FIELD_COUNT];
        areFieldsSet = false;
        areAllFieldsSet = false;
        isSet = new boolean[FIELD_COUNT]; // Remove later
    }

    /**
     * Clears the value in the given time field.
     * @param field the time field to be cleared.
     */
    public final void clear(int field)
    {
        fields[field] = 0;
        stamp[field] = UNSET;
        areFieldsSet = false;
        areAllFieldsSet = false;
        isSet[field] = false; // Remove later
    }

    /**
     * Determines if the given time field has a value set.
     * @return true if the given time field has a value set; false otherwise.
     */