java.util.Calendar Maven / Gradle / Ivy

/*
This is not an official specification document, and usage is restricted.


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This work corresponds to the API signatures of JSR 219: Foundation
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package java.util;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.text.DateFormat;

/** 
 * Calendar is an abstract base class for converting between
 * a Date object and a set of integer fields such as
 * YEAR, MONTH, DAY, HOUR,
 * and so on. (A Date object represents a specific instant in
 * time with millisecond precision. See
 * {@link Date}
 * for information about the Date class.)
 *
 * 

 * Subclasses of Calendar interpret a Date
 * according to the rules of a specific calendar system. The platform
 * provides one concrete subclass of Calendar:
 * GregorianCalendar. Future subclasses could represent
 * the various types of lunar calendars in use in many parts of the world.
 *
 * 

 * Like other locale-sensitive classes, Calendar provides a
 * class method, getInstance, for getting a generally useful
 * object of this type. Calendar's getInstance method
 * returns a Calendar object whose
 * time fields have been initialized with the current date and time:
 * 

 *  * Calendar rightNow = Calendar.getInstance();
 * 
 * 
 *
 * A Calendar object can produce all the time field values
 * needed to implement the date-time formatting for a particular language and
 * calendar style (for example, Japanese-Gregorian, Japanese-Traditional).
 * Calendar defines the range of values returned by certain fields,
 * as well as their meaning.  For example, the first month of the year has value
 * MONTH == JANUARY for all calendars.  Other values
 * are defined by the concrete subclass, such as ERA and
 * YEAR.  See individual field documentation and subclass
 * documentation for details.
 *
 * 
When a Calendar is lenient, it accepts a wider range
 * of field values than it produces.  For example, a lenient
 * GregorianCalendar interprets MONTH ==
 * JANUARY, DAY_OF_MONTH == 32 as February 1.  A
 * non-lenient GregorianCalendar throws an exception when given
 * out-of-range field settings.  When calendars recompute field values for
 * return by get(), they normalize them.  For example, a
 * GregorianCalendar always produces DAY_OF_MONTH
 * values between 1 and the length of the month.
 *
 * 
Calendar defines a locale-specific seven day week using two
 * parameters: the first day of the week and the minimal days in first week
 * (from 1 to 7).  These numbers are taken from the locale resource data when a
 * Calendar is constructed.  They may also be specified explicitly
 * through the API.
 *
 * 
When setting or getting the WEEK_OF_MONTH or
 * WEEK_OF_YEAR fields, Calendar must determine the
 * first week of the month or year as a reference point.  The first week of a
 * month or year is defined as the earliest seven day period beginning on
 * getFirstDayOfWeek() and containing at least
 * getMinimalDaysInFirstWeek() days of that month or year.  Weeks
 * numbered ..., -1, 0 precede the first week; weeks numbered 2, 3,... follow
 * it.  Note that the normalized numbering returned by get() may be
 * different.  For example, a specific Calendar subclass may
 * designate the week before week 1 of a year as week n of the previous
 * year.
 *
 * 
 When computing a Date from time fields, two special
 * circumstances may arise: there may be insufficient information to compute the
 * Date (such as only year and month but no day in the month), or
 * there may be inconsistent information (such as "Tuesday, July 15, 1996" --
 * July 15, 1996 is actually a Monday).
 *
 * 

 * Insufficient information. The calendar will use default
 * information to specify the missing fields. This may vary by calendar; for
 * the Gregorian calendar, the default for a field is the same as that of the
 * start of the epoch: i.e., YEAR = 1970, MONTH = JANUARY, DATE = 1, etc.
 *
 * 

 * Inconsistent information. If fields conflict, the calendar
 * will give preference to fields set more recently. For example, when
 * determining the day, the calendar will look for one of the following
 * combinations of fields.  The most recent combination, as determined by the
 * most recently set single field, will be used.
 *
 * 

 *  * MONTH + DAY_OF_MONTH
 * MONTH + WEEK_OF_MONTH + DAY_OF_WEEK
 * MONTH + DAY_OF_WEEK_IN_MONTH + DAY_OF_WEEK
 * DAY_OF_YEAR
 * DAY_OF_WEEK + WEEK_OF_YEAR
 * 
 * 
 *
 * For the time of day:
 *
 * 
 *  * HOUR_OF_DAY
 * AM_PM + HOUR
 * 
 * 
 *
 * 
 * Note: for some non-Gregorian calendars, different
 * fields may be necessary for complete disambiguation. For example, a full
 * specification of the historical Arabic astronomical calendar requires year,
 * month, day-of-month and day-of-week in some cases.
 *
 * 

 * Note: There are certain possible ambiguities in
 * interpretation of certain singular times, which are resolved in the
 * following ways:
 * 

 *      23:59 is the last minute of the day and 00:00 is the first minute of the
 *          next day. Thus, 23:59 on Dec 31, 1999 < 00:00 on Jan 1, 2000 < 00:01 on
 *          Jan 1, 2000.
 *
 *     
 Although historically not precise, midnight also belongs to "am",
 *          and noon belongs to "pm", so on the same day,
 *          12:00 am (midnight) < 12:01 am, and 12:00 pm (noon) < 12:01 pm
 * 
 *
 * 
 * The date or time format strings are not part of the definition of a
 * calendar, as those must be modifiable or overridable by the user at
 * runtime. Use {@link DateFormat}
 * to format dates.
 *
 * 
Field manipulation methods
 * 
 * Calendar fields can be changed using three methods:
 * set(), add(), and roll().
 * 
 * set(f, value) changes field
 * f to value.  In addition, it sets an
 * internal member variable to indicate that field f has
 * been changed. Although field f is changed immediately,
 * the calendar's milliseconds is not recomputed until the next call to
 * get(), getTime(), or
 * getTimeInMillis() is made. Thus, multiple calls to
 * set() do not trigger multiple, unnecessary
 * computations. As a result of changing a field using
 * set(), other fields may also change, depending on the
 * field, the field value, and the calendar system. In addition,
 * get(f) will not necessarily return value
 * after the fields have been recomputed. The specifics are determined by
 * the concrete calendar class.
 * 
 * Example: Consider a GregorianCalendar
 * originally set to August 31, 1999. Calling set(Calendar.MONTH,
 * Calendar.SEPTEMBER) sets the calendar to September 31,
 * 1999. This is a temporary internal representation that resolves to
 * October 1, 1999 if getTime()is then called. However, a
 * call to set(Calendar.DAY_OF_MONTH, 30) before the call to
 * getTime() sets the calendar to September 30, 1999, since
 * no recomputation occurs after set() itself.
 * 
 * add(f, delta) adds delta
 * to field f.  This is equivalent to calling set(f,
 * get(f) + delta) with two adjustments:
 * 
 * 
 *   Add rule 1. The value of field f
 *   after the call minus the value of field f before the
 *   call is delta, modulo any overflow that has occurred in
 *   field f. Overflow occurs when a field value exceeds its
 *   range and, as a result, the next larger field is incremented or
 *   decremented and the field value is adjusted back into its range.
 * 
 *   Add rule 2. If a smaller field is expected to be
 *   invariant, but   it is impossible for it to be equal to its
 *   prior value because of changes in its minimum or maximum after field
 *   f is changed, then its value is adjusted to be as close
 *   as possible to its expected value. A smaller field represents a
 *   smaller unit of time. HOUR is a smaller field than
 *   DAY_OF_MONTH. No adjustment is made to smaller fields
 *   that are not expected to be invariant. The calendar system
 *   determines what fields are expected to be invariant.
 * 
 * 
 * In addition, unlike set(), add() forces
 * an immediate recomputation of the calendar's milliseconds and all
 * fields.
 * 
 * Example: Consider a GregorianCalendar
 * originally set to August 31, 1999. Calling add(Calendar.MONTH,
 * 13) sets the calendar to September 30, 2000. Add rule
 * 1 sets the MONTH field to September, since
 * adding 13 months to August gives September of the next year. Since
 * DAY_OF_MONTH cannot be 31 in September in a
 * GregorianCalendar, add rule 2 sets the
 * DAY_OF_MONTH to 30, the closest possible value. Although
 * it is a smaller field, DAY_OF_WEEK is not adjusted by
 * rule 2, since it is expected to change when the month changes in a
 * GregorianCalendar.
 * 
 * roll(f, delta) adds
 * delta to field f without changing larger
 * fields. This is equivalent to calling add(f, delta) with
 * the following adjustment:
 * 
 * 
 *   Roll rule. Larger fields are unchanged after the
 *   call. A larger field represents a larger unit of
 *   time. DAY_OF_MONTH is a larger field than
 *   HOUR.
 * 
 * 
 * Example: See {@link java.util.GregorianCalendar#roll(int, int)}.
 * 
 * 
Usage model. To motivate the behavior of
 * add() and roll(), consider a user interface
 * component with increment and decrement buttons for the month, day, and
 * year, and an underlying GregorianCalendar. If the
 * interface reads January 31, 1999 and the user presses the month
 * increment button, what should it read? If the underlying
 * implementation uses set(), it might read March 3, 1999. A
 * better result would be February 28, 1999. Furthermore, if the user
 * presses the month increment button again, it should read March 31,
 * 1999, not March 28, 1999. By saving the original date and using either
 * add() or roll(), depending on whether larger
 * fields should be affected, the user interface can behave as most users
 * will intuitively expect.
 *
 * @see          Date
 * @see          GregorianCalendar
 * @see          TimeZone
 * @see          java.text.DateFormat
 * @version      1.51 10/17/00
 * @author Mark Davis, David Goldsmith, Chen-Lieh Huang, Alan Liu
 * @since JDK1.1
 */
public abstract class Calendar implements Serializable, Cloneable
{
    /** 
     * Field number for get and set indicating the
     * era, e.g., AD or BC in the Julian calendar. This is a calendar-specific
     * value; see subclass documentation.
     * @see GregorianCalendar#AD
     * @see GregorianCalendar#BC
     */
    public static final int ERA = 0;

    /** 
     * Field number for get and set indicating the
     * year. This is a calendar-specific value; see subclass documentation.
     */
    public static final int YEAR = 1;

    /** 
     * Field number for get and set indicating the
     * month. This is a calendar-specific value. The first month of the year is
     * JANUARY which is 0; the last depends on the number of months in a year.
     * @see #JANUARY
     * @see #FEBRUARY
     * @see #MARCH
     * @see #APRIL
     * @see #MAY
     * @see #JUNE
     * @see #JULY
     * @see #AUGUST
     * @see #SEPTEMBER
     * @see #OCTOBER
     * @see #NOVEMBER
     * @see #DECEMBER
     * @see #UNDECIMBER
     */
    public static final int MONTH = 2;

    /** 
     * Field number for get and set indicating the
     * week number within the current year.  The first week of the year, as
     * defined by getFirstDayOfWeek() and
     * getMinimalDaysInFirstWeek(), has value 1.  Subclasses define
     * the value of WEEK_OF_YEAR for days before the first week of
     * the year.
     * @see #getFirstDayOfWeek
     * @see #getMinimalDaysInFirstWeek
     */
    public static final int WEEK_OF_YEAR = 3;

    /** 
     * Field number for get and set indicating the
     * week number within the current month.  The first week of the month, as
     * defined by getFirstDayOfWeek() and
     * getMinimalDaysInFirstWeek(), has value 1.  Subclasses define
     * the value of WEEK_OF_MONTH for days before the first week of
     * the month.
     * @see #getFirstDayOfWeek
     * @see #getMinimalDaysInFirstWeek
     */
    public static final int WEEK_OF_MONTH = 4;

    /** 
     * Field number for get and set indicating the
     * day of the month. This is a synonym for DAY_OF_MONTH.
     * The first day of the month has value 1.
     * @see #DAY_OF_MONTH
     */
    public static final int DATE = 5;

    /** 
     * Field number for get and set indicating the
     * day of the month. This is a synonym for DATE.
     * The first day of the month has value 1.
     * @see #DATE
     */
    public static final int DAY_OF_MONTH = 5;

    /** 
     * Field number for get and set indicating the day
     * number within the current year.  The first day of the year has value 1.
     */
    public static final int DAY_OF_YEAR = 6;

    /** 
     * Field number for get and set indicating the day
     * of the week.  This field takes values SUNDAY,
     * MONDAY, TUESDAY, WEDNESDAY,
     * THURSDAY, FRIDAY, and SATURDAY.
     * @see #SUNDAY
     * @see #MONDAY
     * @see #TUESDAY
     * @see #WEDNESDAY
     * @see #THURSDAY
     * @see #FRIDAY
     * @see #SATURDAY
     */
    public static final int DAY_OF_WEEK = 7;

    /** 
     * Field number for get and set indicating the
     * ordinal number of the day of the week within the current month. Together
     * with the DAY_OF_WEEK field, this uniquely specifies a day
     * within a month.  Unlike WEEK_OF_MONTH and
     * WEEK_OF_YEAR, this field's value does not depend on
     * getFirstDayOfWeek() or
     * getMinimalDaysInFirstWeek().  DAY_OF_MONTH 1
     * through 7 always correspond to DAY_OF_WEEK_IN_MONTH
     * 1; 8 through 14 correspond to
     * DAY_OF_WEEK_IN_MONTH 2, and so on.
     * DAY_OF_WEEK_IN_MONTH 0 indicates the week before
     * DAY_OF_WEEK_IN_MONTH 1.  Negative values count back from the
     * end of the month, so the last Sunday of a month is specified as
     * DAY_OF_WEEK = SUNDAY, DAY_OF_WEEK_IN_MONTH = -1.  Because
     * negative values count backward they will usually be aligned differently
     * within the month than positive values.  For example, if a month has 31
     * days, DAY_OF_WEEK_IN_MONTH -1 will overlap
     * DAY_OF_WEEK_IN_MONTH 5 and the end of 4.
     * @see #DAY_OF_WEEK
     * @see #WEEK_OF_MONTH
     */
    public static final int DAY_OF_WEEK_IN_MONTH = 8;

    /** 
     * Field number for get and set indicating
     * whether the HOUR is before or after noon.
     * E.g., at 10:04:15.250 PM the AM_PM is PM.
     * @see #AM
     * @see #PM
     * @see #HOUR
     */
    public static final int AM_PM = 9;

    /** 
     * Field number for get and set indicating the
     * hour of the morning or afternoon. HOUR is used for the 12-hour
     * clock.
     * E.g., at 10:04:15.250 PM the HOUR is 10.
     * @see #AM_PM
     * @see #HOUR_OF_DAY
     */
    public static final int HOUR = 10;

    /** 
     * Field number for get and set indicating the
     * hour of the day. HOUR_OF_DAY is used for the 24-hour clock.
     * E.g., at 10:04:15.250 PM the HOUR_OF_DAY is 22.
     * @see #HOUR
     */
    public static final int HOUR_OF_DAY = 11;

    /** 
     * Field number for get and set indicating the
     * minute within the hour.
     * E.g., at 10:04:15.250 PM the MINUTE is 4.
     */
    public static final int MINUTE = 12;

    /** 
     * Field number for get and set indicating the
     * second within the minute.
     * E.g., at 10:04:15.250 PM the SECOND is 15.
     */
    public static final int SECOND = 13;

    /** 
     * Field number for get and set indicating the
     * millisecond within the second.
     * E.g., at 10:04:15.250 PM the MILLISECOND is 250.
     */
    public static final int MILLISECOND = 14;

    /** 
     * Field number for get and set
     * indicating the raw offset from GMT in milliseconds.
     * 
     * This field reflects the correct GMT offset value of the time
     * zone of this Calendar if the
     * TimeZone implementation subclass supports
     * historical GMT offset changes.
     */
    public static final int ZONE_OFFSET = 15;

    /** 
     * Field number for get and set indicating the
     * daylight savings offset in milliseconds.
     * 
     * This field reflects the correct daylight saving offset value of
     * the time zone of this Calendar if the
     * TimeZone implementation subclass supports
     * historical Daylight Saving Time schedule changes.
     */
    public static final int DST_OFFSET = 16;

    /** 
     * The number of distinct fields recognized by get and set.
     * Field numbers range from 0..FIELD_COUNT-1.
     */
    public static final int FIELD_COUNT = 17;

    /** 
     * Value of the DAY_OF_WEEK field indicating
     * Sunday.
     */
    public static final int SUNDAY = 1;

    /** 
     * Value of the DAY_OF_WEEK field indicating
     * Monday.
     */
    public static final int MONDAY = 2;

    /** 
     * Value of the DAY_OF_WEEK field indicating
     * Tuesday.
     */
    public static final int TUESDAY = 3;

    /** 
     * Value of the DAY_OF_WEEK field indicating
     * Wednesday.
     */
    public static final int WEDNESDAY = 4;

    /** 
     * Value of the DAY_OF_WEEK field indicating
     * Thursday.
     */
    public static final int THURSDAY = 5;

    /** 
     * Value of the DAY_OF_WEEK field indicating
     * Friday.
     */
    public static final int FRIDAY = 6;

    /** 
     * Value of the DAY_OF_WEEK field indicating
     * Saturday.
     */
    public static final int SATURDAY = 7;

    /** 
     * Value of the MONTH field indicating the
     * first month of the year.
     */
    public static final int JANUARY = 0;

    /** 
     * Value of the MONTH field indicating the
     * second month of the year.
     */
    public static final int FEBRUARY = 1;

    /** 
     * Value of the MONTH field indicating the
     * third month of the year.
     */
    public static final int MARCH = 2;

    /** 
     * Value of the MONTH field indicating the
     * fourth month of the year.
     */
    public static final int APRIL = 3;

    /** 
     * Value of the MONTH field indicating the
     * fifth month of the year.
     */
    public static final int MAY = 4;

    /** 
     * Value of the MONTH field indicating the
     * sixth month of the year.
     */
    public static final int JUNE = 5;

    /** 
     * Value of the MONTH field indicating the
     * seventh month of the year.
     */
    public static final int JULY = 6;

    /** 
     * Value of the MONTH field indicating the
     * eighth month of the year.
     */
    public static final int AUGUST = 7;

    /** 
     * Value of the MONTH field indicating the
     * ninth month of the year.
     */
    public static final int SEPTEMBER = 8;

    /** 
     * Value of the MONTH field indicating the
     * tenth month of the year.
     */
    public static final int OCTOBER = 9;

    /** 
     * Value of the MONTH field indicating the
     * eleventh month of the year.
     */
    public static final int NOVEMBER = 10;

    /** 
     * Value of the MONTH field indicating the
     * twelfth month of the year.
     */
    public static final int DECEMBER = 11;

    /** 
     * Value of the MONTH field indicating the
     * thirteenth month of the year. Although GregorianCalendar
     * does not use this value, lunar calendars do.
     */
    public static final int UNDECIMBER = 12;

    /** 
     * Value of the AM_PM field indicating the
     * period of the day from midnight to just before noon.
     */
    public static final int AM = 0;

    /** 
     * Value of the AM_PM field indicating the
     * period of the day from noon to just before midnight.
     */
    public static final int PM = 1;

    /** 
     * The field values for the currently set time for this calendar.
     * This is an array of FIELD_COUNT integers, with index values
     * ERA through DST_OFFSET.
     * @serial
     */
    protected int[] fields;

    /** 
     * 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.
     * This is an array of FIELD_COUNT booleans, with index values
     * ERA through DST_OFFSET.
     * @serial
     */
    protected boolean[] isSet;

    /** 
     * The currently set time for this calendar, expressed in milliseconds after
     * January 1, 1970, 0:00:00 GMT.
     * @see #isTimeSet
     * @serial
     */
    protected long time;

    /** 
     * True if then the value of time is valid.
     * The time is made invalid by a change to an item of field[].
     * @see #time
     * @serial
     */
    protected boolean isTimeSet;

    /** 
     * True if fields[] are in sync with the currently set time.
     * 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
     * time.
     * @serial
     */
    protected boolean areFieldsSet;

    /** 
     * True if this calendar allows out-of-range field values during computation
     * of time from fields[].
     * @see #setLenient
     * @serial
     */
    private boolean lenient;

    /** 
     * The TimeZone used by this calendar. Calendar
     * uses the time zone data to translate between locale and GMT time.
     * @serial
     */
    private TimeZone zone;

    /** 
     * The first day of the week, with possible values SUNDAY,
     * MONDAY, etc.  This is a locale-dependent value.
     * @serial
     */
    private int firstDayOfWeek;

    /** 
     * The number of days required for the first week in a month or year,
     * with possible values from 1 to 7.  This is a locale-dependent value.
     * @serial
     */
    private int minimalDaysInFirstWeek;

    /** 
     * The next available value for stamp[], an internal array.
     * This actually should not be written out to the stream, and will probably
     * be removed from the stream in the near future.  In the meantime,
     * a value of MINIMUM_USER_STAMP should be used.
     * @serial
     */
    private int nextStamp;

    /** 
     * The version of the serialized data on the stream.  Possible values:
     * 

     * 0 or not present on stream
     * 
     * JDK 1.1.5 or earlier.
     * 
     * 1
     * 
     * JDK 1.1.6 or later.  Writes a correct 'time' value
     * as well as compatible values for other fields.  This is a
     * transitional format.
     * 
     * 
     * When streaming out this class, the most recent format
     * and the highest allowable serialVersionOnStream
     * is written.
     * @serial
     * @since JDK1.1.6
     */
    private int serialVersionOnStream;

    static final long       serialVersionUID = -1807547505821590642L;

    /** 
     * Constructs a Calendar with the default time zone
     * and locale.
     * @see     TimeZone#getDefault
     */
    protected Calendar() { }

    /** 
     * Constructs a calendar with the specified time zone and locale.
     * @param zone the time zone to use
     * @param aLocale the locale for the week data
     */
    protected Calendar(TimeZone zone, Locale aLocale) { }

    /** 
     * Gets a calendar using the default time zone and locale. The
     * Calendar returned is based on the current time
     * in the default time zone with the default locale.
     *
     * @return a Calendar.
     */
    public static Calendar getInstance() {
        return null;
    }

    /** 
     * Gets a calendar using the specified time zone and default locale.
     * The Calendar returned is based on the current time
     * in the given time zone with the default locale. 
     *
     * @param zone the time zone to use
     * @return a Calendar.
     */
    public static Calendar getInstance(TimeZone zone) {
        return null;
    }

    /** 
     * Gets a calendar using the default time zone and specified locale.
     * The Calendar returned is based on the current time
     * in the default time zone with the given locale.
     *
     * @param aLocale the locale for the week data
     * @return a Calendar.
     */
    public static Calendar getInstance(Locale aLocale) {
        return null;
    }

    /** 
     * Gets a calendar with the specified time zone and locale.
     * The Calendar returned is based on the current time
     * in the given time zone with the given locale.
     *
     * @param zone the time zone to use
     * @param aLocale the locale for the week data
     * @return a Calendar.
     */
    public static Calendar getInstance(TimeZone zone, Locale aLocale) {
        return null;
    }

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

    /** 
     * Converts the current field values in fields[]
     * to the millisecond time value
     * time.
     */
    protected abstract void computeTime();

    /** 
     * Converts 
     * the current millisecond time value
     * time
     * to field values in fields[].
     * This allows you to sync up the time field values with
     * a new time that is set for the calendar.  The time is not
     * recomputed first; to recompute the time, then the fields, call the
     * complete method.
     * @see #complete
     */
    protected abstract void computeFields();

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

    /** 
     * Sets this Calendar's current time with the given Date.
     * 
     * Note: Calling setTime() with
     * Date(Long.MAX_VALUE) or Date(Long.MIN_VALUE)
     * may yield incorrect field values from get().
     * @param date the given Date.
     * @see #getTime
     * @see #setTimeInMillis
     */
    public final void setTime(Date date) { }

    /** 
     * Gets this Calendar's current time as a long.
     * @return the current time as UTC milliseconds from the epoch.
     * @see #getTime
     * @see #setTimeInMillis
     */
    public long getTimeInMillis() {
        return -1;
    }

    /** 
     * Sets this Calendar's current time from the given long value.
     * @param millis the new time in UTC milliseconds from the epoch.
     * @see #setTime
     * @see #getTimeInMillis
     */
    public void setTimeInMillis(long millis) { }

    /** 
     * Gets the value for a given time field.
     * @param field the given time field.
     * @return the value for the given time field.
     * @throws ArrayIndexOutOfBoundsException if specified field is out of range
     *             (field < 0 || field >= FIELD_COUNT).
     */
    public int get(int field) {
        return 0;
    }

    /** 
     * 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 0;
    }

    /** 
     * 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.
     * @throws ArrayIndexOutOfBoundsException if specified field is out of range
     *             (field < 0 || field >= FIELD_COUNT).
     */
    public void set(int field, int value) { }

    /** 
     * Sets the values for the fields year, month, and date.
     * Previous values of other fields are retained.  If this is not desired,
     * call clear 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) { }

    /** 
     * 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 clear 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)
    { }

    /** 
     * 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 clear 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)
    { }

    /** 
     * Clears the values of all the time fields.
     */
    public final void clear() { }

    /** 
     * Clears the value in the given time field.
     * @param field the time field to be cleared.
     */
    public final void clear(int field) { }

    /** 
     * Determines if the given time field has a value set.
     * @return true if the given time field has a value set; false otherwise.
     */
    public final boolean isSet(int field) {
        return false;
    }

    /** 
     * Fills in any unset fields in the time field list.
     */
    protected void complete() { }

    /** 
     * Compares this calendar to the specified object.
     * The result is true if and only if the argument is
     * not null and is a Calendar object that
     * represents the same calendar as this object.
     * @param obj the object to compare with.
     * @return true if the objects are the same;
     * false otherwise.
     */
    public boolean equals(Object obj) {
        return false;
    }

    /** 
     * Returns a hash code for this calendar.
     * @return a hash code value for this object. 
     * @since 1.2
     */
    public int hashCode() {
        return 0;
    }

    /** 
     * Compares the time field records.
     * Equivalent to comparing result of conversion to UTC.
     * @param when the Calendar to be compared with this Calendar.
     * @return true if the current time of this Calendar is before
     * the time of Calendar when; false otherwise.
     */
    public boolean before(Object when) {
        return false;
    }

    /** 
     * Compares the time field records.
     * Equivalent to comparing result of conversion to UTC.
     * @param when the Calendar to be compared with this Calendar.
     * @return true if the current time of this Calendar is after
     * the time of Calendar when; false otherwise.
     */
    public boolean after(Object when) {
        return false;
    }

    /** 
     * Date Arithmetic function.
     * Adds the specified (signed) amount of time to the given time field,
     * based on the calendar's rules. For example, to subtract 5 days from
     * the current time of the calendar, you can achieve it by calling:
     * 
add(Calendar.DATE, -5).
     * @param field the time field.
     * @param amount the amount of date or time to be added to the field.
     */
    public abstract void add(int field, int amount);

    /** 
     * Time Field Rolling function.
     * Adds or subtracts (up/down) a single unit of time on the given time 
     * field without changing larger fields. For example, to roll the current 
     * date up by one day, you can achieve it by calling:
     * 
roll(Calendar.DATE, true).
     * When rolling on the year or Calendar.YEAR field, it will roll the year
     * value in the range between 1 and the value returned by calling
     * getMaximum(Calendar.YEAR).
     * When rolling on the month or Calendar.MONTH field, other fields like
     * date might conflict and, need to be changed. For instance,
     * rolling the month on the date 01/31/96 will result in 02/29/96.
     * When rolling on the hour-in-day or Calendar.HOUR_OF_DAY field, it will
     * roll the hour value in the range between 0 and 23, which is zero-based.
     * @param field the time field.
     * @param up indicates if the value of the specified time field is to be
     * rolled up or rolled down. Use true if rolling up, false otherwise.
     * @see Calendar#add
     * @see Calendar#set
     */
    public abstract void roll(int field, boolean up);

    /** 
     * Time Field Rolling function.
     * Add to field a signed amount without changing larger fields.
     * A negative roll amount means to roll down.
     * [NOTE:  This default implementation on Calendar just repeatedly calls the
     * version of roll() that takes a boolean and rolls by one unit.  This may not
     * always do the right thing.  For example, if the DAY_OF_MONTH field is 31,
     * rolling through February will leave it set to 28.  The GregorianCalendar
     * version of this function takes care of this problem.  Other subclasses
     * should also provide overrides of this function that do the right thing.
     * @param field the time field.
     * @param amount the signed amount to add to field.
     * @since 1.2
     * @see Calendar#add
     * @see Calendar#set
     */
    public void roll(int field, int amount) { }

    /** 
     * Sets the time zone with the given time zone value.
     * @param value the given time zone.
     */
    public void setTimeZone(TimeZone value) { }

    /** 
     * Gets the time zone.
     * @return the time zone object associated with this calendar.
     */
    public TimeZone getTimeZone() {
        return null;
    }

    /** 
     * Specify whether or not date/time interpretation is to be lenient.  With
     * lenient interpretation, a date such as "February 942, 1996" will be
     * treated as being equivalent to the 941st day after February 1, 1996.
     * With strict interpretation, such dates will cause an exception to be
     * thrown.
     *
     * @see java.text.DateFormat#setLenient
     */
    public void setLenient(boolean lenient) { }

    /** 
     * Tell whether date/time interpretation is to be lenient.
     */
    public boolean isLenient() {
        return false;
    }

    /** 
     * Sets what the first day of the week is; e.g., Sunday in US,
     * Monday in France.
     * @param value the given first day of the week.
     */
    public void setFirstDayOfWeek(int value) { }

    /** 
     * Gets what the first day of the week is; e.g., Sunday in US,
     * Monday in France.
     * @return the first day of the week.
     */
    public int getFirstDayOfWeek() {
        return 0;
    }

    /** 
     * Sets what the minimal days required in the first week of the year are;
     * For example, if the first week is defined as one that contains the first
     * day of the first month of a year, call the method with value 1. If it
     * must be a full week, use value 7.
     * @param value the given minimal days required in the first week
     * of the year.
     */
    public void setMinimalDaysInFirstWeek(int value) { }

    /** 
     * Gets what the minimal days required in the first week of the year are;
     * e.g., if the first week is defined as one that contains the first day
     * of the first month of a year, getMinimalDaysInFirstWeek returns 1. If
     * the minimal days required must be a full week, getMinimalDaysInFirstWeek
     * returns 7.
     * @return the minimal days required in the first week of the year.
     */
    public int getMinimalDaysInFirstWeek() {
        return 0;
    }

    /** 
     * Gets the minimum value for the given time field.
     * e.g., for Gregorian DAY_OF_MONTH, 1.
     * @param field the given time field.
     * @return the minimum value for the given time field.
     */
    public abstract int getMinimum(int field);

    /** 
     * Gets the maximum value for the given time field.
     * e.g. for Gregorian DAY_OF_MONTH, 31.
     * @param field the given time field.
     * @return the maximum value for the given time field.
     */
    public abstract int getMaximum(int field);

    /** 
     * Gets the highest minimum value for the given field if varies.
     * Otherwise same as getMinimum(). For Gregorian, no difference.
     * @param field the given time field.
     * @return the highest minimum value for the given time field.
     */
    public abstract int getGreatestMinimum(int field);

    /** 
     * Gets the lowest maximum value for the given field if varies.
     * Otherwise same as getMaximum(). e.g., for Gregorian DAY_OF_MONTH, 28.
     * @param field the given time field.
     * @return the lowest maximum value for the given time field.
     */
    public abstract int getLeastMaximum(int field);

    /** 
     * Return the minimum value that this field could have, given the current date.
     * For the Gregorian calendar, this is the same as getMinimum() and getGreatestMinimum().
     *
     * The version of this function on Calendar uses an iterative algorithm to determine the
     * actual minimum value for the field.  There is almost always a more efficient way to
     * accomplish this (in most cases, you can simply return getMinimum()).  GregorianCalendar
     * overrides this function with a more efficient implementation.
     *
     * @param field the field to determine the minimum of
     * @return the minimum of the given field for the current date of this Calendar
     * @since 1.2
     */
    public int getActualMinimum(int field) {
        return 0;
    }

    /** 
     * Return the maximum value that this field could have, given the current date.
     * For example, with the date "Feb 3, 1997" and the DAY_OF_MONTH field, the actual
     * maximum would be 28; for "Feb 3, 1996" it s 29.  Similarly for a Hebrew calendar,
     * for some years the actual maximum for MONTH is 12, and for others 13.
     *
     * The version of this function on Calendar uses an iterative algorithm to determine the
     * actual maximum value for the field.  There is almost always a more efficient way to
     * accomplish this (in most cases, you can simply return getMaximum()).  GregorianCalendar
     * overrides this function with a more efficient implementation.
     *
     * @param field the field to determine the maximum of
     * @return the maximum of the given field for the current date of this Calendar
     * @since 1.2
     */
    public int getActualMaximum(int field) {
        return 0;
    }

    /** 
     * Overrides Cloneable
     */
    public Object clone() {
        return null;
    }

    /** 
     * Return a string representation of this calendar. This method 
     * is intended to be used only for debugging purposes, and the 
     * format of the returned string may vary between implementations. 
     * The returned string may be empty but may not be null.
     * 
     * @return  a string representation of this calendar.
     */
    public String toString() {
        return null;
    }

    /** 
     * Reconstitute this object from a stream (i.e., deserialize it).
     */
    private void readObject(ObjectInputStream stream)
        throws IOException, ClassNotFoundException
    { }

    /** 
     * Save the state of this object to a stream (i.e., serialize it).
     *
     * Ideally, Calendar would only write out its state data and
     * the current time, and not write any field data out, such as
     * fields[], isTimeSet, areFieldsSet,
     * and isSet[].  nextStamp also should not be part
     * of the persistent state. Unfortunately, this didn't happen before JDK 1.1
     * shipped. To be compatible with JDK 1.1, we will always have to write out
     * the field values and state flags.  However, nextStamp can be
     * removed from the serialization stream; this will probably happen in the
     * near future.
     */
    private void writeObject(ObjectOutputStream stream) throws IOException { }
}