Quellcode-Bibliothek Calendar.java

Sprache: JAVA

/*
* Copyright (c) 1996, 2022, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
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*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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*
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/*
* (C) Copyright Taligent, Inc. 1996-1998 - All Rights Reserved
* (C) Copyright IBM Corp. 1996-1998 - All Rights Reserved
*
* The original version of this source code and documentation is copyrighted
* and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
* materials are provided under terms of a License Agreement between Taligent
* and Sun. This technology is protected by multiple US and International
* patents. This notice and attribution to Taligent may not be removed.
* Taligent is a registered trademark of Taligent, Inc.
*
*/

package java.util;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OptionalDataException;
import java.io.Serializable;
import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.PermissionCollection;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.security.ProtectionDomain;
import java.text.DateFormat;
import java.text.DateFormatSymbols;
import java.time.Instant;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import sun.util.BuddhistCalendar;
import sun.util.calendar.ZoneInfo;
import sun.util.locale.provider.CalendarDataUtility;
import sun.util.locale.provider.LocaleProviderAdapter;
import sun.util.locale.provider.TimeZoneNameUtility;
import sun.util.spi.CalendarProvider;

/**
* The {@code Calendar} class is an abstract class that provides methods
* for converting between a specific instant in time and a set of {@link
* #fields calendar fields} such as {@code YEAR}, {@code MONTH},
* {@code DAY_OF_MONTH}, {@code HOUR}, and so on, and for
* manipulating the calendar fields, such as getting the date of the next
* week. An instant in time can be represented by a millisecond value that is
* an offset from the <a id="Epoch">Epoch</a>, January 1, 1970
* 00:00:00.000 GMT (Gregorian).
*
* The class also provides additional fields and methods for
* implementing a concrete calendar system outside the package. Those
* fields and methods are defined as {@code protected}.
*
* 
* Like other locale-sensitive classes, {@code Calendar} provides a
* class method, {@code getInstance}, for getting a generally useful
* object of this type. {@code Calendar}'s {@code getInstance} method
* returns a {@code Calendar} object whose
* calendar fields have been initialized with the current date and time:
* <blockquote>
* <pre>
* Calendar rightNow = Calendar.getInstance();
* </pre>
* </blockquote>
*
* A {@code Calendar} object can produce all the calendar field values
* needed to implement the date-time formatting for a particular language and
* calendar style (for example, Japanese-Gregorian, Japanese-Traditional).
* {@code Calendar} defines the range of values returned by
* certain calendar fields, as well as their meaning. For example,
* the first month of the calendar system has value <code>MONTH ==
* JANUARY</code> for all calendars. Other values are defined by the
* concrete subclass, such as {@code ERA}. See individual field
* documentation and subclass documentation for details.
*
* <h2>Getting and Setting Calendar Field Values</h2>
*
* The calendar field values can be set by calling the {@code set}
* methods. Any field values set in a {@code Calendar} will not be
* interpreted until it needs to calculate its time value (milliseconds from
* the Epoch) or values of the calendar fields. Calling the
* {@code get}, {@code getTimeInMillis}, {@code getTime},
* {@code add} and {@code roll} involves such calculation.
*
* <h3>Leniency</h3>
*
* {@code Calendar} has two modes for interpreting the calendar
* fields, lenient and non-lenient. When a
* {@code Calendar} is in lenient mode, it accepts a wider range of
* calendar field values than it produces. When a {@code Calendar}
* recomputes calendar field values for return by {@code get()}, all of
* the calendar fields are normalized. For example, a lenient
* {@code GregorianCalendar} interprets {@code MONTH == JANUARY},
* {@code DAY_OF_MONTH == 32} as February 1.
*
* When a {@code Calendar} is in non-lenient mode, it throws an
* exception if there is any inconsistency in its calendar fields. For
* example, a {@code GregorianCalendar} always produces
* {@code DAY_OF_MONTH} values between 1 and the length of the month. A
* non-lenient {@code GregorianCalendar} throws an exception upon
* calculating its time or calendar field values if any out-of-range field
* value has been set.
*
* <h3><a id="first_week">First Week</a></h3>
*
* {@code 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 or the
* locale itself when a {@code Calendar} is constructed. If the designated
* locale contains "fw" and/or "rg" <a href="./Locale.html#def_locale_extension">
* Unicode extensions</a>, the first day of the week will be obtained according to
* those extensions. If both "fw" and "rg" are specified, the value from the "fw"
* extension supersedes the implicit one from the "rg" extension.
* They may also be specified explicitly through the methods for setting their
* values.
*
* When setting or getting the {@code WEEK_OF_MONTH} or
* {@code WEEK_OF_YEAR} fields, {@code 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
* {@code getFirstDayOfWeek()} and containing at least
* {@code 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 {@code get()} may be
* different. For example, a specific {@code Calendar} subclass may
* designate the week before week 1 of a year as week <code>n</code> of
* the previous year.
*
* <h3>Calendar Fields Resolution</h3>
*
* When computing a date and time from the calendar fields, there
* may be insufficient information for the computation (such as only
* year and month with no day of month), or there may be inconsistent
* information (such as Tuesday, July 15, 1996 (Gregorian) -- July 15,
* 1996 is actually a Monday). {@code Calendar} will resolve
* calendar field values to determine the date and time in the
* following way.
*
* <a id="resolution">If there is any conflict in calendar field values,
* {@code Calendar} gives priorities to calendar fields that have been set
* more recently.</a> The following are the default combinations of the
* calendar fields. The most recent combination, as determined by the
* most recently set single field, will be used.
*
* <a id="date_resolution">For the date fields</a>:
* <blockquote>
* <pre>
* YEAR + MONTH + DAY_OF_MONTH
* YEAR + MONTH + WEEK_OF_MONTH + DAY_OF_WEEK
* YEAR + MONTH + DAY_OF_WEEK_IN_MONTH + DAY_OF_WEEK
* YEAR + DAY_OF_YEAR
* YEAR + DAY_OF_WEEK + WEEK_OF_YEAR
* </pre></blockquote>
*
* <a id="time_resolution">For the time of day fields</a>:
* <blockquote>
* <pre>
* HOUR_OF_DAY
* AM_PM + HOUR
* </pre></blockquote>
*
* If there are any calendar fields whose values haven't been set in the selected
* field combination, {@code Calendar} uses their default values. The default
* value of each field may vary by concrete calendar systems. For example, in
* {@code GregorianCalendar}, the default of a field is the same as that
* of the start of the Epoch: i.e., {@code YEAR = 1970}, <code>MONTH =
* JANUARY</code>, {@code DAY_OF_MONTH = 1}, etc.
*
* 
* Note: There are certain possible ambiguities in
* interpretation of certain singular times, which are resolved in the
* following ways:
* <ol>
* <li> 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.
*
* <li> 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
* </ol>
*
* 
* 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.
*
* <h3>Field Manipulation</h3>
*
* The calendar fields can be changed using three methods:
* {@code set()}, {@code add()}, and {@code roll()}.
*
* {@code set(f, value)} changes calendar field
* {@code f} to {@code value}. In addition, it sets an
* internal member variable to indicate that calendar field {@code f} has
* been changed. Although calendar field {@code f} is changed immediately,
* the calendar's time value in milliseconds is not recomputed until the next call to
* {@code get()}, {@code getTime()}, {@code getTimeInMillis()},
* {@code add()}, or {@code roll()} is made. Thus, multiple calls to
* {@code set()} do not trigger multiple, unnecessary
* computations. As a result of changing a calendar field using
* {@code set()}, other calendar fields may also change, depending on the
* calendar field, the calendar field value, and the calendar system. In addition,
* {@code get(f)} will not necessarily return {@code value} set by
* the call to the {@code set} method
* after the calendar fields have been recomputed. The specifics are determined by
* the concrete calendar class.
*
* Example: Consider a {@code GregorianCalendar}
* originally set to August 31, 1999. Calling <code>set(Calendar.MONTH,
* Calendar.SEPTEMBER)</code> sets the date to September 31,
* 1999. This is a temporary internal representation that resolves to
* October 1, 1999 if {@code getTime()} is then called. However, a
* call to {@code set(Calendar.DAY_OF_MONTH, 30)} before the call to
* {@code getTime()} sets the date to September 30, 1999, since
* no recomputation occurs after {@code set()} itself.
*
* {@code add(f, delta)} adds {@code delta}
* to field {@code f}. This is equivalent to calling <code>set(f,
* get(f) + delta)</code> with two adjustments:
*
* <blockquote>
* Add rule 1. The value of field {@code f}
* after the call minus the value of field {@code f} before the
* call is {@code delta}, modulo any overflow that has occurred in
* field {@code 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
* {@code f} is changed or other constraints, such as time zone
* offset changes, then its value is adjusted to be as close
* as possible to its expected value. A smaller field represents a
* smaller unit of time. {@code HOUR} is a smaller field than
* {@code 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.
* </blockquote>
*
* In addition, unlike {@code set()}, {@code add()} forces
* an immediate recomputation of the calendar's milliseconds and all
* fields.
*
* Example: Consider a {@code GregorianCalendar}
* originally set to August 31, 1999. Calling <code>add(Calendar.MONTH,
* 13)</code> sets the calendar to September 30, 2000. Add rule
* 1 sets the {@code MONTH} field to September, since
* adding 13 months to August gives September of the next year. Since
* {@code DAY_OF_MONTH} cannot be 31 in September in a
* {@code GregorianCalendar}, add rule 2 sets the
* {@code DAY_OF_MONTH} to 30, the closest possible value. Although
* it is a smaller field, {@code DAY_OF_WEEK} is not adjusted by
* rule 2, since it is expected to change when the month changes in a
* {@code GregorianCalendar}.
*
* {@code roll(f, delta)} adds
* {@code delta} to field {@code f} without changing larger
* fields. This is equivalent to calling {@code add(f, delta)} with
* the following adjustment:
*
* <blockquote>
* Roll rule. Larger fields are unchanged after the
* call. A larger field represents a larger unit of
* time. {@code DAY_OF_MONTH} is a larger field than
* {@code HOUR}.
* </blockquote>
*
* Example: See {@link java.util.GregorianCalendar#roll(int, int)}.
*
* Usage model. To motivate the behavior of
* {@code add()} and {@code roll()}, consider a user interface
* component with increment and decrement buttons for the month, day, and
* year, and an underlying {@code 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 {@code 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
* {@code add()} or {@code roll()}, depending on whether larger
* fields should be affected, the user interface can behave as most users
* will intuitively expect.
*
* @see java.lang.System#currentTimeMillis()
* @see Date
* @see GregorianCalendar
* @see TimeZone
* @see java.text.DateFormat
* @author Mark Davis, David Goldsmith, Chen-Lieh Huang, Alan Liu
* @since 1.1
*/
public abstract class Calendar implements Serializable, Cloneable, Comparable<Calendar> {

 // Data flow in Calendar
 // ---------------------

 // The current time is represented in two ways by Calendar: as UTC
 // milliseconds from the epoch (1 January 1970 0:00 UTC), and as local
 // fields such as MONTH, HOUR, AM_PM, etc. It is possible to compute the
 // millis from the fields, and vice versa. The data needed to do this
 // conversion is encapsulated by a TimeZone object owned by the Calendar.
 // The data provided by the TimeZone object may also be overridden if the
 // user sets the ZONE_OFFSET and/or DST_OFFSET fields directly. The class
 // keeps track of what information was most recently set by the caller, and
 // uses that to compute any other information as needed.

 // If the user sets the fields using set(), the data flow is as follows.
 // This is implemented by the Calendar subclass's computeTime() method.
 // During this process, certain fields may be ignored. The disambiguation
 // algorithm for resolving which fields to pay attention to is described
 // in the class documentation.

 // local fields (YEAR, MONTH, DATE, HOUR, MINUTE, etc.)
 // |
 // | Using Calendar-specific algorithm
 // V
 // local standard millis
 // |
 // | Using TimeZone or user-set ZONE_OFFSET / DST_OFFSET
 // V
 // UTC millis (in time data member)

 // If the user sets the UTC millis using setTime() or setTimeInMillis(),
 // the data flow is as follows. This is implemented by the Calendar
 // subclass's computeFields() method.

 // UTC millis (in time data member)
 // |
 // | Using TimeZone getOffset()
 // V
 // local standard millis
 // |
 // | Using Calendar-specific algorithm
 // V
 // local fields (YEAR, MONTH, DATE, HOUR, MINUTE, etc.)

 // In general, a round trip from fields, through local and UTC millis, and
 // back out to fields is made when necessary. This is implemented by the
 // complete() method. Resolving a partial set of fields into a UTC millis
 // value allows all remaining fields to be generated from that value. If
 // the Calendar is lenient, the fields are also renormalized to standard
 // ranges when they are regenerated.

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

 /**
 * Field number for {@code get} and {@code set} indicating the
 * month. This is a calendar-specific value. The first month of
 * the year in the Gregorian and Julian calendars is
 * {@code 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 {@code get} and {@code set} indicating the
 * week number within the current year. The first week of the year, as
 * defined by {@code getFirstDayOfWeek()} and
 * {@code getMinimalDaysInFirstWeek()}, has value 1. Subclasses define
 * the value of {@code 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 {@code get} and {@code set} indicating the
 * week number within the current month. The first week of the month, as
 * defined by {@code getFirstDayOfWeek()} and
 * {@code getMinimalDaysInFirstWeek()}, has value 1. Subclasses define
 * the value of {@code 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 {@code get} and {@code set} indicating the
 * day of the month. This is a synonym for {@code 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 {@code get} and {@code set} indicating the
 * day of the month. This is a synonym for {@code DATE}.
 * The first day of the month has value 1.
 *
 * @see #DATE
 */
 public static final int DAY_OF_MONTH = 5;

 /**
 * Field number for {@code get} and {@code 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 {@code get} and {@code set} indicating the day
 * of the week. This field takes values {@code SUNDAY},
 * {@code MONDAY}, {@code TUESDAY}, {@code WEDNESDAY},
 * {@code THURSDAY}, {@code FRIDAY}, and {@code 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 {@code get} and {@code set} indicating the
 * ordinal number of the day of the week within the current month. Together
 * with the {@code DAY_OF_WEEK} field, this uniquely specifies a day
 * within a month. Unlike {@code WEEK_OF_MONTH} and
 * {@code WEEK_OF_YEAR}, this field's value does not depend on
 * {@code getFirstDayOfWeek()} or
 * {@code getMinimalDaysInFirstWeek()}. {@code DAY_OF_MONTH 1}
 * through {@code 7} always correspond to <code>DAY_OF_WEEK_IN_MONTH
 * 1</code>; {@code 8} through {@code 14} correspond to
 * {@code DAY_OF_WEEK_IN_MONTH 2}, and so on.
 * {@code DAY_OF_WEEK_IN_MONTH 0} indicates the week before
 * {@code 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
 * {@code 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, {@code DAY_OF_WEEK_IN_MONTH -1} will overlap
 * {@code DAY_OF_WEEK_IN_MONTH 5} and the end of {@code 4}.
 *
 * @see #DAY_OF_WEEK
 * @see #WEEK_OF_MONTH
 */
 public static final int DAY_OF_WEEK_IN_MONTH = 8;

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

 /**
 * Field number for {@code get} and {@code set} indicating the
 * hour of the morning or afternoon. {@code HOUR} is used for the
 * 12-hour clock (0 - 11). Noon and midnight are represented by 0, not by 12.
 * E.g., at 10:04:15.250 PM the {@code HOUR} is 10.
 *
 * @see #AM_PM
 * @see #HOUR_OF_DAY
 */
 public static final int HOUR = 10;

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

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

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

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

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

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

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

 /**
 * Value of the {@link #DAY_OF_WEEK} field indicating
 * Sunday.
 */
 public static final int SUNDAY = 1;

 /**
 * Value of the {@link #DAY_OF_WEEK} field indicating
 * Monday.
 */
 public static final int MONDAY = 2;

 /**
 * Value of the {@link #DAY_OF_WEEK} field indicating
 * Tuesday.
 */
 public static final int TUESDAY = 3;

 /**
 * Value of the {@link #DAY_OF_WEEK} field indicating
 * Wednesday.
 */
 public static final int WEDNESDAY = 4;

 /**
 * Value of the {@link #DAY_OF_WEEK} field indicating
 * Thursday.
 */
 public static final int THURSDAY = 5;

 /**
 * Value of the {@link #DAY_OF_WEEK} field indicating
 * Friday.
 */
 public static final int FRIDAY = 6;

 /**
 * Value of the {@link #DAY_OF_WEEK} field indicating
 * Saturday.
 */
 public static final int SATURDAY = 7;

 /**
 * Value of the {@link #MONTH} field indicating the
 * first month of the year in the Gregorian and Julian calendars.
 */
 public static final int JANUARY = 0;

 /**
 * Value of the {@link #MONTH} field indicating the
 * second month of the year in the Gregorian and Julian calendars.
 */
 public static final int FEBRUARY = 1;

 /**
 * Value of the {@link #MONTH} field indicating the
 * third month of the year in the Gregorian and Julian calendars.
 */
 public static final int MARCH = 2;

 /**
 * Value of the {@link #MONTH} field indicating the
 * fourth month of the year in the Gregorian and Julian calendars.
 */
 public static final int APRIL = 3;

 /**
 * Value of the {@link #MONTH} field indicating the
 * fifth month of the year in the Gregorian and Julian calendars.
 */
 public static final int MAY = 4;

 /**
 * Value of the {@link #MONTH} field indicating the
 * sixth month of the year in the Gregorian and Julian calendars.
 */
 public static final int JUNE = 5;

 /**
 * Value of the {@link #MONTH} field indicating the
 * seventh month of the year in the Gregorian and Julian calendars.
 */
 public static final int JULY = 6;

 /**
 * Value of the {@link #MONTH} field indicating the
 * eighth month of the year in the Gregorian and Julian calendars.
 */
 public static final int AUGUST = 7;

 /**
 * Value of the {@link #MONTH} field indicating the
 * ninth month of the year in the Gregorian and Julian calendars.
 */
 public static final int SEPTEMBER = 8;

 /**
 * Value of the {@link #MONTH} field indicating the
 * tenth month of the year in the Gregorian and Julian calendars.
 */
 public static final int OCTOBER = 9;

 /**
 * Value of the {@link #MONTH} field indicating the
 * eleventh month of the year in the Gregorian and Julian calendars.
 */
 public static final int NOVEMBER = 10;

 /**
 * Value of the {@link #MONTH} field indicating the
 * twelfth month of the year in the Gregorian and Julian calendars.
 */
 public static final int DECEMBER = 11;

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

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

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

 /**
 * A style specifier for {@link #getDisplayNames(int, int, Locale)
 * getDisplayNames} indicating names in all styles, such as
 * "January" and "Jan".
 *
 * @see #SHORT_FORMAT
 * @see #LONG_FORMAT
 * @see #SHORT_STANDALONE
 * @see #LONG_STANDALONE
 * @see #SHORT
 * @see #LONG
 * @since 1.6
 */
 public static final int ALL_STYLES = 0;

 static final int STANDALONE_MASK = 0x8000;

 /**
 * A style specifier for {@link #getDisplayName(int, int, Locale)
 * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
 * getDisplayNames} equivalent to {@link #SHORT_FORMAT}.
 *
 * @see #SHORT_STANDALONE
 * @see #LONG
 * @since 1.6
 */
 public static final int SHORT = 1;

 /**
 * A style specifier for {@link #getDisplayName(int, int, Locale)
 * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
 * getDisplayNames} equivalent to {@link #LONG_FORMAT}.
 *
 * @see #LONG_STANDALONE
 * @see #SHORT
 * @since 1.6
 */
 public static final int LONG = 2;

 /**
 * A style specifier for {@link #getDisplayName(int, int, Locale)
 * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
 * getDisplayNames} indicating a narrow name used for format. Narrow names
 * are typically single character strings, such as "M" for Monday.
 *
 * @see #NARROW_STANDALONE
 * @see #SHORT_FORMAT
 * @see #LONG_FORMAT
 * @since 1.8
 */
 public static final int NARROW_FORMAT = 4;

 /**
 * A style specifier for {@link #getDisplayName(int, int, Locale)
 * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
 * getDisplayNames} indicating a narrow name independently. Narrow names
 * are typically single character strings, such as "M" for Monday.
 *
 * @see #NARROW_FORMAT
 * @see #SHORT_STANDALONE
 * @see #LONG_STANDALONE
 * @since 1.8
 */
 public static final int NARROW_STANDALONE = NARROW_FORMAT | STANDALONE_MASK;

 /**
 * A style specifier for {@link #getDisplayName(int, int, Locale)
 * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
 * getDisplayNames} indicating a short name used for format.
 *
 * @see #SHORT_STANDALONE
 * @see #LONG_FORMAT
 * @see #LONG_STANDALONE
 * @since 1.8
 */
 public static final int SHORT_FORMAT = 1;

 /**
 * A style specifier for {@link #getDisplayName(int, int, Locale)
 * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
 * getDisplayNames} indicating a long name used for format.
 *
 * @see #LONG_STANDALONE
 * @see #SHORT_FORMAT
 * @see #SHORT_STANDALONE
 * @since 1.8
 */
 public static final int LONG_FORMAT = 2;

 /**
 * A style specifier for {@link #getDisplayName(int, int, Locale)
 * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
 * getDisplayNames} indicating a short name used independently,
 * such as a month abbreviation as calendar headers.
 *
 * @see #SHORT_FORMAT
 * @see #LONG_FORMAT
 * @see #LONG_STANDALONE
 * @since 1.8
 */
 public static final int SHORT_STANDALONE = SHORT | STANDALONE_MASK;

 /**
 * A style specifier for {@link #getDisplayName(int, int, Locale)
 * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
 * getDisplayNames} indicating a long name used independently,
 * such as a month name as calendar headers.
 *
 * @see #LONG_FORMAT
 * @see #SHORT_FORMAT
 * @see #SHORT_STANDALONE
 * @since 1.8
 */
 public static final int LONG_STANDALONE = LONG | STANDALONE_MASK;

 // Internal notes:
 // Calendar contains two kinds of time representations: current "time" in
 // milliseconds, and a set of calendar "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 calendar field values for the currently set time for this calendar.
 * This is an array of {@code FIELD_COUNT} integers, with index values
 * {@code ERA} through {@code DST_OFFSET}.
 * @serial
 */
 @SuppressWarnings("ProtectedField")
 protected int fields[];

 /**
 * The flags which tell if a specified calendar 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 {@code FIELD_COUNT} booleans, with index values
 * {@code ERA} through {@code DST_OFFSET}.
 * @serial
 */
 @SuppressWarnings("ProtectedField")
 protected boolean isSet[];

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

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

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

 /**
 * True if {@code 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
 * {@code time}.
 * @serial
 */
 @SuppressWarnings("ProtectedField")
 protected boolean areFieldsSet;

 /**
 * True if all fields have been set.
 * @serial
 */
 transient boolean areAllFieldsSet;

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

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

 /**
 * {@code True} if zone references to a shared TimeZone object.
 */
 private transient boolean sharedZone = false;

 /**
 * The first day of the week, with possible values {@code SUNDAY},
 * {@code 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;

 /**
 * Cache to hold the firstDayOfWeek and minimalDaysInFirstWeek
 * of a Locale.
 */
 private static final ConcurrentMap<Locale, int[]> cachedLocaleData
 = new ConcurrentHashMap<>(3);

 // Special values of stamp[]
 /**
 * The corresponding fields[] has no value.
 */
 private static final int UNSET = 0;

 /**
 * The value of the corresponding fields[] has been calculated internally.
 */
 private static final int COMPUTED = 1;

 /**
 * The value of the corresponding fields[] has been set externally. Stamp
 * values which are greater than 1 represents the (pseudo) time when the
 * corresponding fields[] value was set.
 */
 private static final int MINIMUM_USER_STAMP = 2;

 /**
 * The mask value that represents all of the fields.
 */
 static final int ALL_FIELDS = (1 << FIELD_COUNT) - 1;

 /**
 * The next available value for {@code 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 {@code MINIMUM_USER_STAMP} should be used.
 * @serial
 */
 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;

 /**
 * The version of the serialized data on the stream. Possible values:
 * <dl>
 * <dt>0 or not present on stream</dt>
 * <dd>
 * JDK 1.1.5 or earlier.
 * </dd>
 * <dt>1</dt>
 * <dd>
 * JDK 1.1.6 or later. Writes a correct 'time' value
 * as well as compatible values for other fields. This is a
 * transitional format.
 * </dd>
 * </dl>
 * When streaming out this class, the most recent format
 * and the highest allowable {@code serialVersionOnStream}
 * is written.
 * @serial
 * @since 1.1.6
 */
 private int serialVersionOnStream = currentSerialVersion;

 // Proclaim serialization compatibility with JDK 1.1
 @java.io.Serial
 static final long serialVersionUID = -1807547505821590642L;

 // Mask values for calendar fields
 @SuppressWarnings("PointlessBitwiseExpression")
 static final int ERA_MASK = (1 << ERA);
 static final int YEAR_MASK = (1 << YEAR);
 static final int MONTH_MASK = (1 << MONTH);
 static final int WEEK_OF_YEAR_MASK = (1 << WEEK_OF_YEAR);
 static final int WEEK_OF_MONTH_MASK = (1 << WEEK_OF_MONTH);
 static final int DAY_OF_MONTH_MASK = (1 << DAY_OF_MONTH);
 static final int DAY_OF_YEAR_MASK = (1 << DAY_OF_YEAR);
 static final int DAY_OF_WEEK_MASK = (1 << DAY_OF_WEEK);
 static final int DAY_OF_WEEK_IN_MONTH_MASK = (1 << DAY_OF_WEEK_IN_MONTH);
 static final int AM_PM_MASK = (1 << AM_PM);
 static final int HOUR_MASK = (1 << HOUR);
 static final int HOUR_OF_DAY_MASK = (1 << HOUR_OF_DAY);
 static final int MINUTE_MASK = (1 << MINUTE);
 static final int SECOND_MASK = (1 << SECOND);
 static final int MILLISECOND_MASK = (1 << MILLISECOND);
 static final int ZONE_OFFSET_MASK = (1 << ZONE_OFFSET);
 static final int DST_OFFSET_MASK = (1 << DST_OFFSET);

 /**
 * {@code Calendar.Builder} is used for creating a {@code Calendar} from
 * various date-time parameters.
 *
 * There are two ways to set a {@code Calendar} to a date-time value. One
 * is to set the instant parameter to a millisecond offset from the <a
 * href="Calendar.html#Epoch">Epoch</a>. The other is to set individual
 * field parameters, such as {@link Calendar#YEAR YEAR}, to their desired
 * values. These two ways can't be mixed. Trying to set both the instant and
 * individual fields will cause an {@link IllegalStateException} to be
 * thrown. However, it is permitted to override previous values of the
 * instant or field parameters.
 *
 * If no enough field parameters are given for determining date and/or
 * time, calendar specific default values are used when building a
 * {@code Calendar}. For example, if the {@link Calendar#YEAR YEAR} value
 * isn't given for the Gregorian calendar, 1970 will be used. If there are
 * any conflicts among field parameters, the <a
 * href="Calendar.html#resolution"> resolution rules</a> are applied.
 * Therefore, the order of field setting matters.
 *
 * In addition to the date-time parameters,
 * the {@linkplain #setLocale(Locale) locale},
 * {@linkplain #setTimeZone(TimeZone) time zone},
 * {@linkplain #setWeekDefinition(int, int) week definition}, and
 * {@linkplain #setLenient(boolean) leniency mode} parameters can be set.
 *
 * Examples
 * The following are sample usages. Sample code assumes that the
 * {@code Calendar} constants are statically imported.
 *
 * The following code produces a {@code Calendar} with date 2012-12-31
 * (Gregorian) because Monday is the first day of a week with the <a
 * href="GregorianCalendar.html#iso8601_compatible_setting"> ISO 8601
 * compatible week parameters</a>.
 * <pre>
 * Calendar cal = new Calendar.Builder().setCalendarType("iso8601")
 * .setWeekDate(2013, 1, MONDAY).build();</pre>
 * The following code produces a Japanese {@code Calendar} with date
 * 1989-01-08 (Gregorian), assuming that the default {@link Calendar#ERA ERA}
 * is Heisei that started on that day.
 * <pre>
 * Calendar cal = new Calendar.Builder().setCalendarType("japanese")
 * .setFields(YEAR, 1, DAY_OF_YEAR, 1).build();</pre>
 *
 * @since 1.8
 * @see Calendar#getInstance(TimeZone, Locale)
 * @see Calendar#fields
 */
 public static class Builder {
 private static final int NFIELDS = FIELD_COUNT + 1; // +1 for WEEK_YEAR
 private static final int WEEK_YEAR = FIELD_COUNT;

 private long instant;
 // Calendar.stamp[] (lower half) and Calendar.fields[] (upper half) combined
 private int[] fields;
 // Pseudo timestamp starting from MINIMUM_USER_STAMP.
 // (COMPUTED is used to indicate that the instant has been set.)
 private int nextStamp;
 // maxFieldIndex keeps the max index of fields which have been set.
 // (WEEK_YEAR is never included.)
 private int maxFieldIndex;
 private String type;
 private TimeZone zone;
 private boolean lenient = true;
 private Locale locale;
 private int firstDayOfWeek, minimalDaysInFirstWeek;

 /**
 * Constructs a {@code Calendar.Builder}.
 */
 public Builder() {
 }

 /**
 * Sets the instant parameter to the given {@code instant} value that is
 * a millisecond offset from <a href="Calendar.html#Epoch">the
 * Epoch</a>.
 *
 * @param instant a millisecond offset from the Epoch
 * @return this {@code Calendar.Builder}
 * @throws IllegalStateException if any of the field parameters have
 * already been set
 * @see Calendar#setTime(Date)
 * @see Calendar#setTimeInMillis(long)
 * @see Calendar#time
 */
 public Builder setInstant(long instant) {
 if (fields != null) {
 throw new IllegalStateException();
 }
 this.instant = instant;
 nextStamp = COMPUTED;
 return this;
 }

 /**
 * Sets the instant parameter to the {@code instant} value given by a
 * {@link Date}. This method is equivalent to a call to
 * {@link #setInstant(long) setInstant(instant.getTime())}.
 *
 * @param instant a {@code Date} representing a millisecond offset from
 * the Epoch
 * @return this {@code Calendar.Builder}
 * @throws NullPointerException if {@code instant} is {@code null}
 * @throws IllegalStateException if any of the field parameters have
 * already been set
 * @see Calendar#setTime(Date)
 * @see Calendar#setTimeInMillis(long)
 * @see Calendar#time
 */
 public Builder setInstant(Date instant) {
 return setInstant(instant.getTime()); // NPE if instant == null
 }

 /**
 * Sets the {@code field} parameter to the given {@code value}.
 * {@code field} is an index to the {@link Calendar#fields}, such as
 * {@link Calendar#DAY_OF_MONTH DAY_OF_MONTH}. Field value validation is
 * not performed in this method. Any out of range values are either
 * normalized in lenient mode or detected as an invalid value in
 * non-lenient mode when building a {@code Calendar}.
 *
 * @param field an index to the {@code Calendar} fields
 * @param value the field value
 * @return this {@code Calendar.Builder}
 * @throws IllegalArgumentException if {@code field} is invalid
 * @throws IllegalStateException if the instant value has already been set,
 * or if fields have been set too many
 * (approximately {@link Integer#MAX_VALUE}) times.
 * @see Calendar#set(int, int)
 */
 public Builder set(int field, int value) {
 // Note: WEEK_YEAR can't be set with this method.
 if (field < 0 || field >= FIELD_COUNT) {
 throw new IllegalArgumentException("field is invalid");
 }
 if (isInstantSet()) {
 throw new IllegalStateException("instant has been set");
 }
 allocateFields();
 internalSet(field, value);
 return this;
 }

 /**
 * Sets field parameters to their values given by
 * {@code fieldValuePairs} that are pairs of a field and its value.
 * For example,
 * <pre>
 * setFields(Calendar.YEAR, 2013,
 * Calendar.MONTH, Calendar.DECEMBER,
 * Calendar.DAY_OF_MONTH, 23);</pre>
 * is equivalent to the sequence of the following
 * {@link #set(int, int) set} calls:
 * <pre>
 * set(Calendar.YEAR, 2013)
 * .set(Calendar.MONTH, Calendar.DECEMBER)
 * .set(Calendar.DAY_OF_MONTH, 23);</pre>
 *
 * @param fieldValuePairs field-value pairs
 * @return this {@code Calendar.Builder}
 * @throws NullPointerException if {@code fieldValuePairs} is {@code null}
 * @throws IllegalArgumentException if any of fields are invalid,
 * or if {@code fieldValuePairs.length} is an odd number.
 * @throws IllegalStateException if the instant value has been set,
 * or if fields have been set too many (approximately
 * {@link Integer#MAX_VALUE}) times.
 */
 public Builder setFields(int... fieldValuePairs) {
 int len = fieldValuePairs.length;
 if ((len % 2) != 0) {
 throw new IllegalArgumentException();
 }
 if (isInstantSet()) {
 throw new IllegalStateException("instant has been set");
 }
 if ((nextStamp + len / 2) < 0) {
 throw new IllegalStateException("stamp counter overflow");
 }
 allocateFields();
 for (int i = 0; i < len; ) {
 int field = fieldValuePairs[i++];
 // Note: WEEK_YEAR can't be set with this method.
 if (field < 0 || field >= FIELD_COUNT) {
 throw new IllegalArgumentException("field is invalid");
 }
 internalSet(field, fieldValuePairs[i++]);
 }
 return this;
 }

 /**
 * Sets the date field parameters to the values given by {@code year},
 * {@code month}, and {@code dayOfMonth}. This method is equivalent to
 * a call to:
 * <pre>
 * setFields(Calendar.YEAR, year,
 * Calendar.MONTH, month,
 * Calendar.DAY_OF_MONTH, dayOfMonth);</pre>
 *
 * @param year the {@link Calendar#YEAR YEAR} value
 * @param month the {@link Calendar#MONTH MONTH} value
 * (the month numbering is 0-based).
 * @param dayOfMonth the {@link Calendar#DAY_OF_MONTH DAY_OF_MONTH} value
 * @return this {@code Calendar.Builder}
 */
 public Builder setDate(int year, int month, int dayOfMonth) {
 return setFields(YEAR, year, MONTH, month, DAY_OF_MONTH, dayOfMonth);
 }

 /**
 * Sets the time of day field parameters to the values given by
 * {@code hourOfDay}, {@code minute}, and {@code second}. This method is
 * equivalent to a call to:
 * <pre>
 * setTimeOfDay(hourOfDay, minute, second, 0);</pre>
 *
 * @param hourOfDay the {@link Calendar#HOUR_OF_DAY HOUR_OF_DAY} value
 * (24-hour clock)
 * @param minute the {@link Calendar#MINUTE MINUTE} value
 * @param second the {@link Calendar#SECOND SECOND} value
 * @return this {@code Calendar.Builder}
 */
 public Builder setTimeOfDay(int hourOfDay, int minute, int second) {
 return setTimeOfDay(hourOfDay, minute, second, 0);
 }

 /**
 * Sets the time of day field parameters to the values given by
 * {@code hourOfDay}, {@code minute}, {@code second}, and
 * {@code millis}. This method is equivalent to a call to:
 * <pre>
 * setFields(Calendar.HOUR_OF_DAY, hourOfDay,
 * Calendar.MINUTE, minute,
 * Calendar.SECOND, second,
 * Calendar.MILLISECOND, millis);</pre>
 *
 * @param hourOfDay the {@link Calendar#HOUR_OF_DAY HOUR_OF_DAY} value
 * (24-hour clock)
 * @param minute the {@link Calendar#MINUTE MINUTE} value
 * @param second the {@link Calendar#SECOND SECOND} value
 * @param millis the {@link Calendar#MILLISECOND MILLISECOND} value
 * @return this {@code Calendar.Builder}
 */
 public Builder setTimeOfDay(int hourOfDay, int minute, int second, int millis) {
 return setFields(HOUR_OF_DAY, hourOfDay, MINUTE, minute,
 SECOND, second, MILLISECOND, millis);
 }

 /**
 * Sets the week-based date parameters to the values with the given
 * date specifiers - week year, week of year, and day of week.
 *
 * If the specified calendar doesn't support week dates, the
 * {@link #build() build} method will throw an {@link IllegalArgumentException}.
 *
 * @param weekYear the week year
 * @param weekOfYear the week number based on {@code weekYear}
 * @param dayOfWeek the day of week value: one of the constants
 * for the {@link Calendar#DAY_OF_WEEK DAY_OF_WEEK} field:
 * {@link Calendar#SUNDAY SUNDAY}, ..., {@link Calendar#SATURDAY SATURDAY}.
 * @return this {@code Calendar.Builder}
 * @see Calendar#setWeekDate(int, int, int)
 * @see Calendar#isWeekDateSupported()
 */
 public Builder setWeekDate(int weekYear, int weekOfYear, int dayOfWeek) {
 allocateFields();
 internalSet(WEEK_YEAR, weekYear);
 internalSet(WEEK_OF_YEAR, weekOfYear);
 internalSet(DAY_OF_WEEK, dayOfWeek);
 return this;
 }

 /**
 * Sets the time zone parameter to the given {@code zone}. If no time
 * zone parameter is given to this {@code Calendar.Builder}, the
 * {@linkplain TimeZone#getDefault() default
 * {@code TimeZone}} will be used in the {@link #build() build}
 * method.
 *
 * @param zone the {@link TimeZone}
 * @return this {@code Calendar.Builder}
 * @throws NullPointerException if {@code zone} is {@code null}
 * @see Calendar#setTimeZone(TimeZone)
 */
 public Builder setTimeZone(TimeZone zone) {
 if (zone == null) {
 throw new NullPointerException();
 }
 this.zone = zone;
 return this;
 }

 /**
 * Sets the lenient mode parameter to the value given by {@code lenient}.
 * If no lenient parameter is given to this {@code Calendar.Builder},
 * lenient mode will be used in the {@link #build() build} method.
 *
 * @param lenient {@code true} for lenient mode;
 * {@code false} for non-lenient mode
 * @return this {@code Calendar.Builder}
 * @see Calendar#setLenient(boolean)
 */
 public Builder setLenient(boolean lenient) {
 this.lenient = lenient;
 return this;
 }

 /**
 * Sets the calendar type parameter to the given {@code type}. The
 * calendar type given by this method has precedence over any explicit
 * or implicit calendar type given by the
 * {@linkplain #setLocale(Locale) locale}.
 *
 * In addition to the available calendar types returned by the
 * {@link Calendar#getAvailableCalendarTypes() Calendar.getAvailableCalendarTypes}
 * method, {@code "gregorian"} and {@code "iso8601"} as aliases of
 * {@code "gregory"} can be used with this method.
 *
 * @param type the calendar type
 * @return this {@code Calendar.Builder}
 * @throws NullPointerException if {@code type} is {@code null}
 * @throws IllegalArgumentException if {@code type} is unknown
 * @throws IllegalStateException if another calendar type has already been set
 * @see Calendar#getCalendarType()
 * @see Calendar#getAvailableCalendarTypes()
 */
 public Builder setCalendarType(String type) {
 if (type.equals("gregorian")) { // NPE if type == null
 type = "gregory";
 }
 if (!Calendar.getAvailableCalendarTypes().contains(type)
 && !type.equals("iso8601")) {
 throw new IllegalArgumentException("unknown calendar type: " + type);
 }
 if (this.type == null) {
 this.type = type;
 } else {
 if (!this.type.equals(type)) {
 throw new IllegalStateException("calendar type override");
 }
 }
 return this;
 }

 /**
 * Sets the locale parameter to the given {@code locale}. If no locale
 * is given to this {@code Calendar.Builder}, the {@linkplain
 * Locale#getDefault(Locale.Category) default {@code Locale}}
 * for {@link Locale.Category#FORMAT} will be used.
 *
 * If no calendar type is explicitly given by a call to the
 * {@link #setCalendarType(String) setCalendarType} method,
 * the {@code Locale} value is used to determine what type of
 * {@code Calendar} to be built.
 *
 * If no week definition parameters are explicitly given by a call to
 * the {@link #setWeekDefinition(int,int) setWeekDefinition} method, the
 * {@code Locale}'s default values are used.
 *
 * @param locale the {@link Locale}
 * @throws NullPointerException if {@code locale} is {@code null}
 * @return this {@code Calendar.Builder}
 * @see Calendar#getInstance(Locale)
 */
 public Builder setLocale(Locale locale) {
 if (locale == null) {
 throw new NullPointerException();
 }
 this.locale = locale;
 return this;
 }

 /**
 * Sets the week definition parameters to the values given by
 * {@code firstDayOfWeek} and {@code minimalDaysInFirstWeek} that are
 * used to determine the <a href="Calendar.html#first_week">first
 * week</a> of a year. The parameters given by this method have
 * precedence over the default values given by the
 * {@linkplain #setLocale(Locale) locale}.
 *
 * @param firstDayOfWeek the first day of a week; one of
 * {@link Calendar#SUNDAY} to {@link Calendar#SATURDAY}
 * @param minimalDaysInFirstWeek the minimal number of days in the first
 * week (1..7)
 * @return this {@code Calendar.Builder}
 * @throws IllegalArgumentException if {@code firstDayOfWeek} or
 * {@code minimalDaysInFirstWeek} is invalid
 * @see Calendar#getFirstDayOfWeek()
 * @see Calendar#getMinimalDaysInFirstWeek()
 */
 public Builder setWeekDefinition(int firstDayOfWeek, int minimalDaysInFirstWeek) {
 if (!isValidWeekParameter(firstDayOfWeek)
 || !isValidWeekParameter(minimalDaysInFirstWeek)) {
 throw new IllegalArgumentException();
 }
 this.firstDayOfWeek = firstDayOfWeek;
 this.minimalDaysInFirstWeek = minimalDaysInFirstWeek;
 return this;
 }

 /**
 * Returns a {@code Calendar} built from the parameters set by the
 * setter methods. The calendar type given by the {@link #setCalendarType(String)
 * setCalendarType} method or the {@linkplain #setLocale(Locale) locale} is
 * used to determine what {@code Calendar} to be created. If no explicit
 * calendar type is given, the locale's default calendar is created.
 *
 * If the calendar type is {@code "iso8601"}, the
 * {@linkplain GregorianCalendar#setGregorianChange(Date) Gregorian change date}
 * of a {@link GregorianCalendar} is set to {@code Date(Long.MIN_VALUE)}
 * to be the proleptic Gregorian calendar. Its week definition
 * parameters are also set to be <a
 * href="GregorianCalendar.html#iso8601_compatible_setting">compatible
 * with the ISO 8601 standard</a>. Note that the
 * {@link GregorianCalendar#getCalendarType() getCalendarType} method of
 * a {@code GregorianCalendar} created with {@code "iso8601"} returns
 * {@code "gregory"}.
 *
 * The default values are used for locale and time zone if these
 * parameters haven't been given explicitly.
 * 
 * If the locale contains the time zone with "tz"
 * <a href="Locale.html#def_locale_extension">Unicode extension</a>,
 * and time zone hasn't been given explicitly, time zone in the locale
 * is used.
 *
 * Any out of range field values are either normalized in lenient
 * mode or detected as an invalid value in non-lenient mode.
 *
 * @return a {@code Calendar} built with parameters of this {@code
 * Calendar.Builder}
 * @throws IllegalArgumentException if the calendar type is unknown, or
 * if any invalid field values are given in non-lenient mode, or
 * if a week date is given for the calendar type that doesn't
 * support week dates.
 * @see Calendar#getInstance(TimeZone, Locale)
 * @see Locale#getDefault(Locale.Category)
 * @see TimeZone#getDefault()
 */
 public Calendar build() {
 if (locale == null) {
 locale = Locale.getDefault();
 }
 if (zone == null) {
 zone = defaultTimeZone(locale);
 }
 if (type == null) {
 type = locale.getUnicodeLocaleType("ca");
 }
 if (type == null) {
 if (locale.getCountry() == "TH"
 && locale.getLanguage() == "th") {
 type = "buddhist";
 } else {
 type = "gregory";
 }
 }
 final Calendar cal = switch (type) {
 case "gregory" -> new GregorianCalendar(zone, locale, true);
 case "iso8601" -> {
 GregorianCalendar gcal = new GregorianCalendar(zone, locale, true);
 // make gcal a proleptic Gregorian
 gcal.setGregorianChange(new Date(Long.MIN_VALUE));
 // and week definition to be compatible with ISO 8601
 setWeekDefinition(MONDAY, 4);
 yield gcal;
 }
 case "buddhist" -> {
 var buddhistCalendar = new BuddhistCalendar(zone, locale);
 buddhistCalendar.clear();
 yield buddhistCalendar;
 }
 case "japanese" -> new JapaneseImperialCalendar(zone, locale, true);
 default -> throw new IllegalArgumentException("unknown calendar type: " + type);
 };
 cal.setLenient(lenient);
 if (firstDayOfWeek != 0) {
 cal.setFirstDayOfWeek(firstDayOfWeek);
 cal.setMinimalDaysInFirstWeek(minimalDaysInFirstWeek);
 }
 if (isInstantSet()) {
 cal.setTimeInMillis(instant);
 cal.complete();
 return cal;
 }

 if (fields != null) {
 boolean weekDate = isSet(WEEK_YEAR)
 && fields[WEEK_YEAR] > fields[YEAR];
 if (weekDate && !cal.isWeekDateSupported()) {
 throw new IllegalArgumentException("week date is unsupported by " + type);
 }

 // Set the fields from the min stamp to the max stamp so that
 // the fields resolution works in the Calendar.
 for (int stamp = MINIMUM_USER_STAMP; stamp < nextStamp; stamp++) {
 for (int index = 0; index <= maxFieldIndex; index++) {
 if (fields[index] == stamp) {
 cal.set(index, fields[NFIELDS + index]);
 break;
 }
 }
 }

 if (weekDate) {
 int weekOfYear = isSet(WEEK_OF_YEAR) ? fields[NFIELDS + WEEK_OF_YEAR] : 1;
 int dayOfWeek = isSet(DAY_OF_WEEK)
 ? fields[NFIELDS + DAY_OF_WEEK] : cal.getFirstDayOfWeek();
 cal.setWeekDate(fields[NFIELDS + WEEK_YEAR], weekOfYear, dayOfWeek);
 }
 cal.complete();
 }

 return cal;
 }

 private void allocateFields() {
 if (fields == null) {
 fields = new int[NFIELDS * 2];
 nextStamp = MINIMUM_USER_STAMP;
 maxFieldIndex = -1;
 }
 }

 private void internalSet(int field, int value) {
 fields[field] = nextStamp++;
 if (nextStamp < 0) {
 throw new IllegalStateException("stamp counter overflow");
 }
 fields[NFIELDS + field] = value;
 if (field > maxFieldIndex && field < WEEK_YEAR) {
 maxFieldIndex = field;
 }
 }

 private boolean isInstantSet() {
 return nextStamp == COMPUTED;
 }

 private boolean isSet(int index) {
 return fields != null && fields[index] > UNSET;
 }

 private boolean isValidWeekParameter(int value) {
 return value > 0 && value <= 7;
 }
 }

 /**
 * Constructs a Calendar with the default time zone
 * and the default {@link java.util.Locale.Category#FORMAT FORMAT}
 * locale.
 * @see TimeZone#getDefault
 */
 protected Calendar()
 {
 this(TimeZone.getDefaultRef(), Locale.getDefault(Locale.Category.FORMAT));
 sharedZone = true;
 }

 /**
 * 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)
 {
 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 time zone and locale. The
 * {@code Calendar} returned is based on the current time
 * in the default time zone with the default
 * {@link Locale.Category#FORMAT FORMAT} locale.
 * 
 * If the locale contains the time zone with "tz"
 * <a href="Locale.html#def_locale_extension">Unicode extension</a>,
 * that time zone is used instead.
 *
 * @return a Calendar.
 */
 public static Calendar getInstance()
 {
 Locale aLocale = Locale.getDefault(Locale.Category.FORMAT);
 return createCalendar(defaultTimeZone(aLocale), aLocale);
 }

 /**
 * Gets a calendar using the specified time zone and default locale.
 * The {@code Calendar} returned is based on the current time
 * in the given time zone with the default
 * {@link Locale.Category#FORMAT FORMAT} locale.
 *
 * @param zone the time zone to use
 * @return a Calendar.
 */
 public static Calendar getInstance(TimeZone zone)
 {
 return createCalendar(zone, Locale.getDefault(Locale.Category.FORMAT));
 }

 /**
 * Gets a calendar using the default time zone and specified locale.
 * The {@code Calendar} returned is based on the current time
 * in the default time zone with the given locale.
 * 
 * If the locale contains the time zone with "tz"
 * <a href="Locale.html#def_locale_extension">Unicode extension</a>,
 * that time zone is used instead.
 *
 * @param aLocale the locale for the week data
 * @return a Calendar.
 */
 public static Calendar getInstance(Locale aLocale)
 {
 return createCalendar(defaultTimeZone(aLocale), aLocale);
 }

 /**
 * Gets a calendar with the specified time zone and locale.
 * The {@code 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 createCalendar(zone, aLocale);
 }

 private static TimeZone defaultTimeZone(Locale l) {
 TimeZone defaultTZ = TimeZone.getDefault();
 String shortTZID = l.getUnicodeLocaleType("tz");
 return shortTZID != null ?
 TimeZoneNameUtility.convertLDMLShortID(shortTZID)
 .map(TimeZone::getTimeZone)
 .orElse(defaultTZ) :
 defaultTZ;
 }

 private static Calendar createCalendar(TimeZone zone,
 Locale aLocale)
 {
 CalendarProvider provider =
 LocaleProviderAdapter.getAdapter(CalendarProvider.class, aLocale)
 .getCalendarProvider();
 if (provider != null) {
 try {
 return provider.getInstance(zone, aLocale);
 } catch (IllegalArgumentException iae) {
 // fall back to the default instantiation
 }
 }

 Calendar cal = null;

 if (aLocale.hasExtensions()) {
 String caltype = aLocale.getUnicodeLocaleType("ca");
 if (caltype != null) {
 cal = switch (caltype) {
 case "buddhist" -> new BuddhistCalendar(zone, aLocale);
 case "japanese" -> new JapaneseImperialCalendar(zone, aLocale);
 case "gregory" -> new GregorianCalendar(zone, aLocale);
 default -> null;
 };
 }
 }
 if (cal == null) {
 // If no known calendar type is explicitly specified,
 // perform the traditional way to create a Calendar:
 // create a BuddhistCalendar for th_TH locale,
 // a JapaneseImperialCalendar for ja_JP_JP locale, or
 // a GregorianCalendar for any other locales.
 // NOTE: The language, country and variant strings are interned.
 if (aLocale.getLanguage() == "th" && aLocale.getCountry() == "TH") {
 cal = new BuddhistCalendar(zone, aLocale);
 } else if (aLocale.getVariant() == "JP" && aLocale.getLanguage() == "ja"
 && aLocale.getCountry() == "JP") {
 cal = new JapaneseImperialCalendar(zone, aLocale);
 } else {
 cal = new GregorianCalendar(zone, aLocale);
 }
 }
 return cal;
 }

 /**
 * Returns an array of all locales for which the {@code getInstance}
 * methods of this class can return localized instances.
 * At a minimum, the returned array must contain a {@code Locale} instance equal to
 * {@link Locale#ROOT Locale.ROOT} and a {@code Locale} instance equal to
 * {@link Locale#US Locale.US}.
 *
 * @return An array of locales for which localized
 * {@code Calendar} instances are available.
 */
 public static synchronized Locale[] getAvailableLocales()
 {
 return DateFormat.getAvailableLocales();
 }

 /**
 * Converts the current calendar field values in {@link #fields fields[]}
 * to the millisecond time value
 * {@link #time}.
 *
 * @see #complete()
 * @see #computeFields()
 */
 protected abstract void computeTime();

 /**
 * Converts the current millisecond time value {@link #time}
 * to calendar field values in {@link #fields fields[]}.
 * This allows you to sync up the calendar 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
 * {@link #complete()} method.
 *
 * @see #computeTime()
 */
 protected abstract void computeFields();

 /**
 * Returns a {@code Date} object representing this
 * {@code Calendar}'s time value (millisecond offset from the <a
 * href="#Epoch">Epoch</a>").
 *
 * @return a {@code Date} representing the time value.
 * @see #setTime(Date)
 * @see #getTimeInMillis()
 */
 public final Date getTime() {
 return new Date(getTimeInMillis());
 }

 /**
 * Sets this Calendar's time with the given {@code Date}.
 * 
 * Note: Calling {@code setTime()} with
 * {@code Date(Long.MAX_VALUE)} or {@code Date(Long.MIN_VALUE)}
 * may yield incorrect field values from {@code get()}.
 *
 * @param date the given Date.
 * @see #getTime()
 * @see #setTimeInMillis(long)
 * @throws NullPointerException if {@code date} is {@code null}
 */
 public final void setTime(Date date) {
 Objects.requireNonNull(date, "date must not be null");
 setTimeInMillis(date.getTime());
 }

 /**
 * Returns this Calendar's time value in milliseconds.
 *
 * @return the current time as UTC milliseconds from the epoch.
 * @see #getTime()
 * @see #setTimeInMillis(long)
 */
 public long getTimeInMillis() {
 if (!isTimeSet) {
 updateTime();
 }
 return time;
 }

 /**
 * Sets this Calendar's current time from the given long value.
 *
 * @param millis the new time in UTC milliseconds from the epoch.
 * @see #setTime(Date)
 * @see #getTimeInMillis()
 */
 public void setTimeInMillis(long millis) {
 // If we don't need to recalculate the calendar field values,
 // do nothing.
 if (time == millis && isTimeSet && areFieldsSet && areAllFieldsSet
 && (zone instanceof ZoneInfo) && !((ZoneInfo)zone).isDirty()) {
 return;
 }
 time = millis;
 isTimeSet = true;
 areFieldsSet = false;
 computeFields();
 areAllFieldsSet = areFieldsSet = true;
 }

 /**
 * Returns the value of the given calendar field. In lenient mode,
 * all calendar fields are normalized. In non-lenient mode, all
 * calendar fields are validated and this method throws an
 * exception if any calendar fields have out-of-range values. The
 * normalization and validation are handled by the
 * {@link #complete()} method, which process is calendar
 * system dependent.
 *
 * @param field the given calendar field.
 * @return the value for the given calendar field.
 * @throws ArrayIndexOutOfBoundsException if the specified field is out of range
 * (<code>field < 0 || field >= FIELD_COUNT</code>).
 * @see #set(int,int)
 * @see #complete()
 */
 public int get(int field)
 {
 complete();
 return internalGet(field);
 }

 /**
 * Returns the value of the given calendar field. This method does
 * not involve normalization or validation of the field value.
 *
 * @param field the given calendar field.
 * @return the value for the given calendar field.
 * @see #get(int)
 */
 protected final int internalGet(int field)
 {
 return fields[field];
 }

 /**
 * Sets the value of the given calendar field. This method does
 * not affect any setting state of the field in this
 * {@code Calendar} instance.
 *
 * @throws IndexOutOfBoundsException if the specified field is out of range
 * (<code>field < 0 || field >= FIELD_COUNT</code>).
 * @see #areFieldsSet
 * @see #isTimeSet
 * @see #areAllFieldsSet
 * @see #set(int,int)
 */
 final void internalSet(int field, int value)
 {
 fields[field] = value;
 }

 /**
 * Sets the given calendar field to the given value. The value is not
 * interpreted by this method regardless of the leniency mode.
 *
 * @param field the given calendar field.
 * @param value the value to be set for the given calendar field.
 * @throws ArrayIndexOutOfBoundsException if the specified field is out of range
 * (<code>field < 0 || field >= FIELD_COUNT</code>).
 * in non-lenient mode.
 * @see #set(int,int,int)
 * @see #set(int,int,int,int,int)
 * @see #set(int,int,int,int,int,int)
 * @see #get(int)
 */
 public void set(int field, int value)
 {
 // If the fields are partially normalized, calculate all the
 // fields before changing any fields.
 if (areFieldsSet && !areAllFieldsSet) {
 computeFields();
 }
 internalSet(field, value);
 isTimeSet = false;
 areFieldsSet = false;
 isSet[field] = true;
 stamp[field] = nextStamp++;
 if (nextStamp == Integer.MAX_VALUE) {
 adjustStamp();
 }
 }

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

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

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

 /**
 * Sets all the calendar field values and the time value
 * (millisecond offset from the <a href="#Epoch">Epoch</a>) of
 * this {@code Calendar} undefined. This means that {@link
 * #isSet(int) isSet()} will return {@code false} for all the
 * calendar fields, and the date and time calculations will treat
 * the fields as if they had never been set. A
 * {@code Calendar} implementation class may use its specific
 * default field values for date/time calculations. For example,
 * {@code GregorianCalendar} uses 1970 if the
 * {@code YEAR} field value is undefined.
 *
 * @see #clear(int)
 */
 public final void clear()
 {
 for (int i = 0; i < fields.length; ) {
 stamp[i] = fields[i] = 0; // UNSET == 0
 isSet[i++] = false;
 }
 areAllFieldsSet = areFieldsSet = false;
 isTimeSet = false;
 }

 /**
 * Sets the given calendar field value and the time value
 * (millisecond offset from the <a href="#Epoch">Epoch</a>) of
 * this {@code Calendar} undefined. This means that {@link
 * #isSet(int) isSet(field)} will return {@code false}, and
 * the date and time calculations will treat the field as if it
 * had never been set. A {@code Calendar} implementation
 * class may use the field's specific default value for date and
 * time calculations.
 *
 * The {@link #HOUR_OF_DAY}, {@link #HOUR} and {@link #AM_PM}
 * fields are handled independently and the <a
 * href="#time_resolution">the resolution rule for the time of
 * day</a> is applied. Clearing one of the fields doesn't reset
 * the hour of day value of this {@code Calendar}. Use {@link
 * #set(int,int) set(Calendar.HOUR_OF_DAY, 0)} to reset the hour
 * value.
 *
 * @param field the calendar field to be cleared.
 * @see #clear()
 */
 public final void clear(int field)
 {
 fields[field] = 0;
 stamp[field] = UNSET;
 isSet[field] = false;

 areAllFieldsSet = areFieldsSet = false;
 isTimeSet = false;
 }

 /**
 * Determines if the given calendar field has a value set,
 * including cases that the value has been set by internal fields
 * calculations triggered by a {@code get} method call.
 *
 * @param field the calendar field to test
 * @return {@code true} if the given calendar field has a value set;
 * {@code false} otherwise.
 */
 public final boolean isSet(int field)
 {
 return stamp[field] != UNSET;
 }

 /**
 * Returns the string representation of the calendar
 * {@code field} value in the given {@code style} and
 * {@code locale}. If no string representation is
 * applicable, {@code null} is returned. This method calls
 * {@link Calendar#get(int) get(field)} to get the calendar
 * {@code field} value if the string representation is
 * applicable to the given calendar {@code field}.
 *
 * For example, if this {@code Calendar} is a
 * {@code GregorianCalendar} and its date is 2005-01-01, then
 * the string representation of the {@link #MONTH} field would be
 * "January" in the long style in an English locale or "Jan" in
 * the short style. However, no string representation would be
 * available for the {@link #DAY_OF_MONTH} field, and this method
 * would return {@code null}.
 *
 * The default implementation supports the calendar fields for
 * which a {@link DateFormatSymbols} has names in the given
 * {@code locale}.
 *
 * @param field
 * the calendar field for which the string representation
 * is returned
 * @param style
 * the style applied to the string representation; one of {@link
 * #SHORT_FORMAT} ({@link #SHORT}), {@link #SHORT_STANDALONE},
 * {@link #LONG_FORMAT} ({@link #LONG}), {@link #LONG_STANDALONE},
 * {@link #NARROW_FORMAT}, or {@link #NARROW_STANDALONE}.
 * @param locale
 * the locale for the string representation
 * (any calendar types specified by {@code locale} are ignored)
 * @return the string representation of the given
 * {@code field} in the given {@code style}, or
 * {@code null} if no string representation is
 * applicable.
 * @throws IllegalArgumentException
 * if {@code field} or {@code style} is invalid,
 * or if this {@code Calendar} is non-lenient and any
 * of the calendar fields have invalid values
 * @throws NullPointerException
 * if {@code locale} is null
 * @since 1.6
 */
 public String getDisplayName(int field, int style, Locale locale) {
 if (!checkDisplayNameParams(field, style, SHORT, NARROW_FORMAT, locale,
 ERA_MASK|MONTH_MASK|DAY_OF_WEEK_MASK|AM_PM_MASK)) {
 return null;
 }

 String calendarType = getCalendarType();
 int fieldValue = get(field);
 // the standalone/narrow styles and short era are supported only through
 // CalendarNameProviders.
 if (isStandaloneStyle(style) || isNarrowFormatStyle(style) ||
 field == ERA && (style & SHORT) == SHORT) {
 String val = CalendarDataUtility.retrieveFieldValueName(calendarType,
 field, fieldValue,
 style, locale);
 // Perform fallback here to follow the CLDR rules
 if (val == null) {
 if (isNarrowFormatStyle(style)) {
 val = CalendarDataUtility.retrieveFieldValueName(calendarType,
 field, fieldValue,
 toStandaloneStyle(style),
 locale);
 } else if (isStandaloneStyle(style)) {
 val = CalendarDataUtility.retrieveFieldValueName(calendarType,
 field, fieldValue,
 getBaseStyle(style),
 locale);
 }
 }
 return val;
 }

 DateFormatSymbols symbols = DateFormatSymbols.getInstance(locale);
 String[] strings = getFieldStrings(field, style, symbols);
 if (strings != null) {
 if (fieldValue < strings.length) {
 return strings[fieldValue];
 }
 }
 return null;
 }

 /**
 * Returns a {@code Map} containing all names of the calendar
 * {@code field} in the given {@code style} and
 * {@code locale} and their corresponding field values. For
 * example, if this {@code Calendar} is a {@link
 * GregorianCalendar}, the returned map would contain "Jan" to
 * {@link #JANUARY}, "Feb" to {@link #FEBRUARY}, and so on, in the
 * {@linkplain #SHORT short} style in an English locale.
 *
 * Narrow names may not be unique due to use of single characters,
 * such as "S" for Sunday and Saturday. In that case narrow names are not
 * included in the returned {@code Map}.
 *
 * The values of other calendar fields may be taken into
 * account to determine a set of display names. For example, if
 * this {@code Calendar} is a lunisolar calendar system and
 * the year value given by the {@link #YEAR} field has a leap
 * month, this method would return month names containing the leap
 * month name, and month names are mapped to their values specific
 * for the year.
 *
 * The default implementation supports display names contained in
 * a {@link DateFormatSymbols}. For example, if {@code field}
 * is {@link #MONTH} and {@code style} is {@link
 * #ALL_STYLES}, this method returns a {@code Map} containing
 * all strings returned by {@link DateFormatSymbols#getShortMonths()}
 * and {@link DateFormatSymbols#getMonths()}.
 *
 * @param field
 * the calendar field for which the display names are returned
 * @param style
 * the style applied to the string representation; one of {@link
 * #SHORT_FORMAT} ({@link #SHORT}), {@link #SHORT_STANDALONE},
 * {@link #LONG_FORMAT} ({@link #LONG}), {@link #LONG_STANDALONE},
 * {@link #NARROW_FORMAT}, or {@link #NARROW_STANDALONE}
 * @param locale
 * the locale for the display names
 * @return a {@code Map} containing all display names in
 * {@code style} and {@code locale} and their
 * field values, or {@code null} if no display names
 * are defined for {@code field}
 * @throws IllegalArgumentException
 * if {@code field} or {@code style} is invalid,
 * or if this {@code Calendar} is non-lenient and any
 * of the calendar fields have invalid values
 * @throws NullPointerException
 * if {@code locale} is null
 * @since 1.6
 */
 public Map<String, Integer> getDisplayNames(int field, int style, Locale locale) {
 if (!checkDisplayNameParams(field, style, ALL_STYLES, NARROW_FORMAT, locale,
 ERA_MASK|MONTH_MASK|DAY_OF_WEEK_MASK|AM_PM_MASK)) {
 return null;
 }

 String calendarType = getCalendarType();
 if (style == ALL_STYLES || isStandaloneStyle(style) || isNarrowFormatStyle(style) ||
 field == ERA && (style & SHORT) == SHORT) {
 Map<String, Integer> map;
 map = CalendarDataUtility.retrieveFieldValueNames(calendarType, field, style, locale);

 // Perform fallback here to follow the CLDR rules
 if (map == null) {
 if (isNarrowFormatStyle(style)) {
 map = CalendarDataUtility.retrieveFieldValueNames(calendarType, field,
 toStandaloneStyle(style), locale);
 } else if (style != ALL_STYLES) {
 map = CalendarDataUtility.retrieveFieldValueNames(calendarType, field,
 getBaseStyle(style), locale);
 }
 }
 return map;
 }

 // SHORT or LONG
 return getDisplayNamesImpl(field, style, locale);
 }

 private Map<String,Integer> getDisplayNamesImpl(int field, int style, Locale locale) {
 DateFormatSymbols symbols = DateFormatSymbols.getInstance(locale);
 String[] strings = getFieldStrings(field, style, symbols);
 if (strings != null) {
 Map<String,Integer> names = new HashMap<>();
 for (int i = 0; i < strings.length; i++) {
 if (strings[i].isEmpty()) {
 continue;
 }
 names.put(strings[i], i);
 }
 return names;
 }
 return null;
 }

 boolean checkDisplayNameParams(int field, int style, int minStyle, int maxStyle,
 Locale locale, int fieldMask) {
 int baseStyle = getBaseStyle(style); // Ignore the standalone mask
 if (field < 0 || field >= fields.length ||
 baseStyle < minStyle || baseStyle > maxStyle || baseStyle == 3) {
 throw new IllegalArgumentException();
 }
 if (locale == null) {
 throw new NullPointerException();
 }
 return isFieldSet(fieldMask, field);
 }

 private String[] getFieldStrings(int field, int style, DateFormatSymbols symbols) {
 int baseStyle = getBaseStyle(style); // ignore the standalone mask

 // DateFormatSymbols doesn't support any narrow names.
 if (baseStyle == NARROW_FORMAT) {
 return null;
 }

 return switch (field) {
 case ERA -> symbols.getEras();
 case MONTH -> (baseStyle == LONG) ? symbols.getMonths() : symbols.getShortMonths();
 case DAY_OF_WEEK -> (baseStyle == LONG) ? symbols.getWeekdays() : symbols.getShortWeekdays();
 case AM_PM -> symbols.getAmPmStrings();
 default -> null;
 };
 }

 /**
 * Fills in any unset fields in the calendar fields. First, the {@link
 * #computeTime()} method is called if the time value (millisecond offset
 * from the <a href="#Epoch">Epoch</a>) has not been calculated from
 * calendar field values. Then, the {@link #computeFields()} method is
 * called to calculate all calendar field values.
 */
 protected void complete()
 {
 if (!isTimeSet) {
 updateTime();
 }
 if (!areFieldsSet || !areAllFieldsSet) {
 computeFields(); // fills in unset fields
 areAllFieldsSet = areFieldsSet = true;
 }
 }

 /**
 * Returns whether the value of the specified calendar field has been set
 * externally by calling one of the setter methods rather than by the
 * internal time calculation.
 *
 * @return {@code true} if the field has been set externally,
 * {@code false} otherwise.
 * @throws IndexOutOfBoundsException if the specified
 * {@code field} is out of range
 * (<code>field < 0 || field >= FIELD_COUNT</code>).
 * @see #selectFields()
 * @see #setFieldsComputed(int)
 */
 final boolean isExternallySet(int field) {
 return stamp[field] >= MINIMUM_USER_STAMP;
 }

 /**
 * Returns a field mask (bit mask) indicating all calendar fields that
 * have the state of externally or internally set.
 *
 * @return a bit mask indicating set state fields
 */
 final int getSetStateFields() {
 int mask = 0;
 for (int i = 0; i < fields.length; i++) {
 if (stamp[i] != UNSET) {
 mask |= 1 << i;
 }
 }
 return mask;
 }

 /**
 * Sets the state of the specified calendar fields to
 * computed. This state means that the specified calendar fields
 * have valid values that have been set by internal time calculation
 * rather than by calling one of the setter methods.
 *
 * @param fieldMask the field to be marked as computed.
 * @throws IndexOutOfBoundsException if the specified
 * {@code field} is out of range
 * (<code>field < 0 || field >= FIELD_COUNT</code>).
 * @see #isExternallySet(int)
 * @see #selectFields()
 */
 final void setFieldsComputed(int fieldMask) {
 if (fieldMask == ALL_FIELDS) {
 for (int i = 0; i < fields.length; i++) {
 stamp[i] = COMPUTED;
 isSet[i] = true;
 }
 areFieldsSet = areAllFieldsSet = true;
 } else {
 for (int i = 0; i < fields.length; i++) {
 if ((fieldMask & 1) == 1) {
 stamp[i] = COMPUTED;
 isSet[i] = true;
 } else {
 if (areAllFieldsSet && !isSet[i]) {
 areAllFieldsSet = false;
 }
 }
 fieldMask >>>= 1;
 }
 }
 }

 /**
 * Sets the state of the calendar fields that are not specified
 * by {@code fieldMask} to unset. If {@code fieldMask}
 * specifies all the calendar fields, then the state of this
 * {@code Calendar} becomes that all the calendar fields are in sync
 * with the time value (millisecond offset from the Epoch).
 *
 * @param fieldMask the field mask indicating which calendar fields are in
 * sync with the time value.
 * @throws IndexOutOfBoundsException if the specified
 * {@code field} is out of range
 * (<code>field < 0 || field >= FIELD_COUNT</code>).
 * @see #isExternallySet(int)
 * @see #selectFields()
 */
 final void setFieldsNormalized(int fieldMask) {
 if (fieldMask != ALL_FIELDS) {
 for (int i = 0; i < fields.length; i++) {
 if ((fieldMask & 1) == 0) {
 stamp[i] = fields[i] = 0; // UNSET == 0
 isSet[i] = false;
 }
 fieldMask >>= 1;
 }
 }

 // Some or all of the fields are in sync with the
 // milliseconds, but the stamp values are not normalized yet.
 areFieldsSet = true;
 areAllFieldsSet = false;
 }

 /**
 * Returns whether the calendar fields are partially in sync with the time
 * value or fully in sync but not stamp values are not normalized yet.
 */
 final boolean isPartiallyNormalized() {
 return areFieldsSet && !areAllFieldsSet;
 }

 /**
 * Returns whether the calendar fields are fully in sync with the time
 * value.
 */
 final boolean isFullyNormalized() {
 return areFieldsSet && areAllFieldsSet;
 }

 /**
 * Marks this Calendar as not sync'd.
 */
 final void setUnnormalized() {
 areFieldsSet = areAllFieldsSet = false;
 }

 /**
 * Returns whether the specified {@code field} is on in the
 * {@code fieldMask}.
 */
 static boolean isFieldSet(int fieldMask, int field) {
 return (fieldMask & (1 << field)) != 0;
 }

 /**
 * Returns a field mask indicating which calendar field values
 * to be used to calculate the time value. The calendar fields are
 * returned as a bit mask, each bit of which corresponds to a field, i.e.,
 * the mask value of {@code field} is <code>(1 <<
 * field)</code>. For example, 0x26 represents the {@code YEAR},
 * {@code MONTH}, and {@code DAY_OF_MONTH} fields (i.e., 0x26 is
 * equal to
 * <code>(1<<YEAR)|(1<<MONTH)|(1<<DAY_OF_MONTH))</code>.
 *
 * This method supports the calendar fields resolution as described in
 * the class description. If the bit mask for a given field is on and its
 * field has not been set (i.e., {@code isSet(field)} is
 * {@code false}), then the default value of the field has to be
 * used, which case means that the field has been selected because the
 * selected combination involves the field.
 *
 * @return a bit mask of selected fields
 * @see #isExternallySet(int)
 */
 final int selectFields() {
 // This implementation has been taken from the GregorianCalendar class.

 // The YEAR field must always be used regardless of its SET
 // state because YEAR is a mandatory field to determine the date
 // and the default value (EPOCH_YEAR) may change through the
 // normalization process.
 int fieldMask = YEAR_MASK;

 if (stamp[ERA] != UNSET) {
 fieldMask |= ERA_MASK;
 }
 // Find the most recent group of fields specifying the day within
 // the year. These may be any of the following combinations:
 // MONTH + DAY_OF_MONTH
 // MONTH + WEEK_OF_MONTH + DAY_OF_WEEK
 // MONTH + DAY_OF_WEEK_IN_MONTH + DAY_OF_WEEK
 // DAY_OF_YEAR
 // WEEK_OF_YEAR + DAY_OF_WEEK
 // We look for the most recent of the fields in each group to determine
 // the age of the group. For groups involving a week-related field such
 // as WEEK_OF_MONTH, DAY_OF_WEEK_IN_MONTH, or WEEK_OF_YEAR, both the
 // week-related field and the DAY_OF_WEEK must be set for the group as a
 // whole to be considered. (See bug 4153860 - liu 7/24/98.)
 int dowStamp = stamp[DAY_OF_WEEK];
 int monthStamp = stamp[MONTH];
 int domStamp = stamp[DAY_OF_MONTH];
 int womStamp = aggregateStamp(stamp[WEEK_OF_MONTH], dowStamp);
 int dowimStamp = aggregateStamp(stamp[DAY_OF_WEEK_IN_MONTH], dowStamp);
 int doyStamp = stamp[DAY_OF_YEAR];
 int woyStamp = aggregateStamp(stamp[WEEK_OF_YEAR], dowStamp);

 int bestStamp = domStamp;
 if (womStamp > bestStamp) {
 bestStamp = womStamp;
 }
 if (dowimStamp > bestStamp) {
 bestStamp = dowimStamp;
 }
 if (doyStamp > bestStamp) {
 bestStamp = doyStamp;
 }
 if (woyStamp > bestStamp) {
 bestStamp = woyStamp;
 }

 /* No complete combination exists. Look for WEEK_OF_MONTH,
 * DAY_OF_WEEK_IN_MONTH, or WEEK_OF_YEAR alone. Treat DAY_OF_WEEK alone
 * as DAY_OF_WEEK_IN_MONTH.
 */
 if (bestStamp == UNSET) {
 womStamp = stamp[WEEK_OF_MONTH];
 dowimStamp = Math.max(stamp[DAY_OF_WEEK_IN_MONTH], dowStamp);
 woyStamp = stamp[WEEK_OF_YEAR];
 bestStamp = Math.max(Math.max(womStamp, dowimStamp), woyStamp);

 /* Treat MONTH alone or no fields at all as DAY_OF_MONTH. This may
 * result in bestStamp = domStamp = UNSET if no fields are set,
 * which indicates DAY_OF_MONTH.
 */
 if (bestStamp == UNSET) {
 bestStamp = domStamp = monthStamp;
 }
 }

 if (bestStamp == domStamp ||
 (bestStamp == womStamp && stamp[WEEK_OF_MONTH] >= stamp[WEEK_OF_YEAR]) ||
 (bestStamp == dowimStamp && stamp[DAY_OF_WEEK_IN_MONTH] >= stamp[WEEK_OF_YEAR])) {
 fieldMask |= MONTH_MASK;
 if (bestStamp == domStamp) {
 fieldMask |= DAY_OF_MONTH_MASK;
 } else {
 assert (bestStamp == womStamp || bestStamp == dowimStamp);
 if (dowStamp != UNSET) {
 fieldMask |= DAY_OF_WEEK_MASK;
 }
 if (womStamp == dowimStamp) {
 // When they are equal, give the priority to
 // WEEK_OF_MONTH for compatibility.
 if (stamp[WEEK_OF_MONTH] >= stamp[DAY_OF_WEEK_IN_MONTH]) {
 fieldMask |= WEEK_OF_MONTH_MASK;
 } else {
 fieldMask |= DAY_OF_WEEK_IN_MONTH_MASK;
 }
 } else {
 if (bestStamp == womStamp) {
 fieldMask |= WEEK_OF_MONTH_MASK;
 } else {
 assert (bestStamp == dowimStamp);
 if (stamp[DAY_OF_WEEK_IN_MONTH] != UNSET) {
 fieldMask |= DAY_OF_WEEK_IN_MONTH_MASK;
 }
 }
 }
 }
 } else {
 assert (bestStamp == doyStamp || bestStamp == woyStamp ||
 bestStamp == UNSET);
 if (bestStamp == doyStamp) {
 fieldMask |= DAY_OF_YEAR_MASK;
 } else {
 assert (bestStamp == woyStamp);
 if (dowStamp != UNSET) {
 fieldMask |= DAY_OF_WEEK_MASK;
 }
 fieldMask |= WEEK_OF_YEAR_MASK;
 }
 }

 // Find the best set of fields specifying the time of day. There
 // are only two possibilities here; the HOUR_OF_DAY or the
 // AM_PM and the HOUR.
 int hourOfDayStamp = stamp[HOUR_OF_DAY];
 int hourStamp = aggregateStamp(stamp[HOUR], stamp[AM_PM]);
 bestStamp = (hourStamp > hourOfDayStamp) ? hourStamp : hourOfDayStamp;

 // if bestStamp is still UNSET, then take HOUR or AM_PM. (See 4846659)
 if (bestStamp == UNSET) {
 bestStamp = Math.max(stamp[HOUR], stamp[AM_PM]);
 }

 // Hours
 if (bestStamp != UNSET) {
 if (bestStamp == hourOfDayStamp) {
 fieldMask |= HOUR_OF_DAY_MASK;
 } else {
 fieldMask |= HOUR_MASK;
 if (stamp[AM_PM] != UNSET) {
 fieldMask |= AM_PM_MASK;
 }
 }
 }
 if (stamp[MINUTE] != UNSET) {
 fieldMask |= MINUTE_MASK;
 }
 if (stamp[SECOND] != UNSET) {
 fieldMask |= SECOND_MASK;
 }
 if (stamp[MILLISECOND] != UNSET) {
 fieldMask |= MILLISECOND_MASK;
 }
 if (stamp[ZONE_OFFSET] >= MINIMUM_USER_STAMP) {
 fieldMask |= ZONE_OFFSET_MASK;
 }
 if (stamp[DST_OFFSET] >= MINIMUM_USER_STAMP) {
 fieldMask |= DST_OFFSET_MASK;
 }

 return fieldMask;
 }

 int getBaseStyle(int style) {
 return style & ~STANDALONE_MASK;
 }

 private int toStandaloneStyle(int style) {
 return style | STANDALONE_MASK;
 }

 private boolean isStandaloneStyle(int style) {
 return (style & STANDALONE_MASK) != 0;
 }

 private boolean isNarrowStyle(int style) {
 return style == NARROW_FORMAT || style == NARROW_STANDALONE;
 }

 private boolean isNarrowFormatStyle(int style) {
 return style == NARROW_FORMAT;
 }

 /**
 * Returns the pseudo-time-stamp for two fields, given their
 * individual pseudo-time-stamps. If either of the fields
 * is unset, then the aggregate is unset. Otherwise, the
 * aggregate is the later of the two stamps.
 */
 private static int aggregateStamp(int stamp_a, int stamp_b) {
 if (stamp_a == UNSET || stamp_b == UNSET) {
 return UNSET;
 }
 return (stamp_a > stamp_b) ? stamp_a : stamp_b;
 }

 /**
 * Returns an unmodifiable {@code Set} containing all calendar types
 * supported by {@code Calendar} in the runtime environment. The available
 * calendar types can be used for the <a
 * href="Locale.html#def_locale_extension">Unicode locale extensions</a>.
 * The {@code Set} returned contains at least {@code "gregory"}. The
 * calendar types don't include aliases, such as {@code "gregorian"} for
 * {@code "gregory"}.
 *
 * @return an unmodifiable {@code Set} containing all available calendar types
 * @since 1.8
 * @see #getCalendarType()
 * @see Calendar.Builder#setCalendarType(String)
 * @see Locale#getUnicodeLocaleType(String)
 */
 public static Set<String> getAvailableCalendarTypes() {
 return AvailableCalendarTypes.SET;
 }

 private static class AvailableCalendarTypes {
 private static final Set<String> SET = Set.of("gregory", "buddhist", "japanese");
 private AvailableCalendarTypes() {
 }
 }

 /**
 * Returns the calendar type of this {@code Calendar}. Calendar types are
 * defined by the Unicode Locale Data Markup Language (LDML)
 * specification.
 *
 * The default implementation of this method returns the class name of
 * this {@code Calendar} instance. Any subclasses that implement
 * LDML-defined calendar systems should override this method to return
 * appropriate calendar types.
 *
 * @return the LDML-defined calendar type or the class name of this
 * {@code Calendar} instance
 * @since 1.8
 * @see <a href="Locale.html#def_extensions">Locale extensions</a>
 * @see Locale.Builder#setLocale(Locale)
 * @see Locale.Builder#setUnicodeLocaleKeyword(String, String)
 */
 public String getCalendarType() {
 return this.getClass().getName();
 }

 /**
 * Compares this {@code Calendar} to the specified
 * {@code Object}. The result is {@code true} if and only if
 * the argument is a {@code Calendar} object of the same calendar
 * system that represents the same time value (millisecond offset from the
 * <a href="#Epoch">Epoch</a>) under the same
 * {@code Calendar} parameters as this object.
 *
 * The {@code Calendar} parameters are the values represented
 * by the {@code isLenient}, {@code getFirstDayOfWeek},
 * {@code getMinimalDaysInFirstWeek} and {@code getTimeZone}
 * methods. If there is any difference in those parameters
 * between the two {@code Calendar}s, this method returns
 * {@code false}.
 *
 * Use the {@link #compareTo(Calendar) compareTo} method to
 * compare only the time values.
 *
 * @param obj the object to compare with.
 * @return {@code true} if this object is equal to {@code obj};
 * {@code false} otherwise.
 */
 @SuppressWarnings("EqualsWhichDoesntCheckParameterClass")
 @Override
 public boolean equals(Object obj) {
 if (this == obj) {
 return true;
 }
 try {
 Calendar that = (Calendar)obj;
 return compareTo(getMillisOf(that)) == 0 &&
 lenient == that.lenient &&
 firstDayOfWeek == * particularfile subject tothe"" exception asasprovided
 minimalDaysInFirstWeek == that.minimalDaysInFirstWeek &&
 (zoneinstanceof ?
 zone.equals(that.zone) :
 zone.equals(that.getTimeZone()));
 } catch (Exception e) {
 // Note: GregorianCalendar.computeTime throws
 // IllegalArgumentException if the ERA value is invalid
 // even it's in lenient mode.
 }
 return false;
 }

*
 * Returns /*
 *
 * @return a hash code value for this object.
 * @since 1.2
 */
 @Override
 public int hashCode() {
 // 'otheritems' represents the hash code for the previous versions.
 int otheritems = (lenient ? 1 : 0)
 | (firstDayOfWeek << 1)
 | (minimalDaysInFirstWeek << 4)
 | (zone.hashCode() << 7);
 long t = getMillisOf(this);
 return (int) t ^ (int)(t >> 32) ^ otheritems;

 /**
 * Returns whether this {@code Calendar} represents a time
 * before the time represented by the specified
 * {@code Object}. This method is equivalent to:
 * <pre>{@code
 * compareTo(when) < 0
 * }</pre>
 * if and only if {@code when} is a {@code Calendar}
 * instance. Otherwise, the method returns {@code false}.
 *
 * @param when the {@code Object} to be compared
 * @return {@code true} if the time of this
 * {@code Calendar} is before the time represented by
 * {@code when}; {@code false} otherwise.
 * @see #compareTo(Calendar)
 */
 public boolean before(Object when) {
 return when instanceof Calendar
 && compareTo((Calendar)when) < 0;
 }

 /**
 * Returns whether this {@code Calendar} represents a time
 * after the time represented by the specified
 * {@code Object}. This method is equivalent to:
 * <pre>{@code
 * compareTo(when) > 0
 * }</pre>
 * if and only if {@code when} is a {@code Calendar}
 * instance. Otherwise, the method returns {@code false}.
 *
 * @param when the {@code Object} to be compared
 * @return {@code true} if the time of this {@code Calendar} is
 * after the time represented by {@code when}; {@code false}
 * otherwise.
 * @see #compareTo(Calendar)
 */
 public boolean after(Object when) {
 return when instanceof Calendar
 && compareTo((Calendar)when) > 0;
 }

 /**
 * Compares the time values (millisecond offsets from the <a
 * href="#Epoch">Epoch</a>) represented by two
 * {@code Calendar} objects.
 *
 * @param anotherCalendar the {@code Calendar} to be compared.
 * @return the value {@code 0} if the time represented by the argument
 * is equal to the time represented by this {@code Calendar}; a value
 * less than {@code 0} if the time of this {@code Calendar} is
 * before the time represented by the argument; and a value greater than
 * {@code 0} if the time of this {@code Calendar} is after the
 * time represented by the argument.
 * @throws NullPointerException if the specified {@code Calendar} is
 * {@code null}.
 * @throws IllegalArgumentException if the time value of the
 * specified {@code Calendar} object can't be obtained due to
 * any invalid calendar values.
 * @since 1.5
 */
 @Override
 public int compareTo(Calendar anotherCalendar) {
 return compareTo(getMillisOf(anotherCalendar));
 }

 /**
 * Adds or subtracts the specified amount of time to the given calendar 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:
 * {@code add(Calendar.DAY_OF_MONTH, -5)}.
 *
 * @param field the calendar field.
 * @param amount the amount of date or time to be added to the field.
 * @see #roll(int,int)
 * @see #set(int,int)
 */
 public abstract void add(int field, int amount);

 /**
 * 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
 * {@code 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(int,int)
 * @see Calendar#set(int,int)
 */
 public abstract void roll(int field, boolean up);

 /**
 * Adds the specified (signed) amount to the specified calendar field
 * without changing larger fields. A negative amount means to roll
 * down.
 *
 * NOTE: This default implementation on {@code Calendar} just repeatedly calls the
 * version of {@link #roll(int,boolean) roll()} that rolls by one unit. This may not
 * always do the right thing. For example, if the {@code DAY_OF_MONTH} field is 31,
 * rolling through February will leave it set to 28. The {@code 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 calendar field.
 * @param amount the signed amount to add to the calendar {@code field}.
 * @since 1.2
 * @see #roll(int,boolean)
 * @see #add(int,int)
 * @see #set(int,int)
 */
 public void roll(int field, int amount)
 {
 while (amount > 0) {
 roll(field, true);
 amount--;
 }
 while (amount < 0) {
 roll(field, false);
 amount++;
 }
 }

 /**
 * Sets the time zone with the given time zone value.
 *
 * @param value the given time zone.
 */
 public void setTimeZone(TimeZone value)
 {
 zone = value;
 sharedZone = false;
 /* Recompute the fields from the time using the new zone. This also
 * works if isTimeSet is false (after a call to set()). In that case
 * the time will be computed from the fields using the new zone, then
 * the fields will get recomputed from that. Consider the sequence of
 * calls: cal.setTimeZone(EST); cal.set(HOUR, 1); cal.setTimeZone(PST).
 * Is cal set to 1 o'clock EST or 1 o'clock PST? Answer: PST. More
 * generally, a call to setTimeZone() affects calls to set() BEFORE AND
 * AFTER it up to the next call to complete().
 */
 areAllFieldsSet = areFieldsSet = false;
 }

 /**
 * Gets the time zone.
 *
 * @return the time zone object associated with this calendar.
 */
 public TimeZone getTimeZone()
 {
 // If the TimeZone object is shared by other Calendar instances, then
 // create a clone.
 if (sharedZone) {
 zone = (TimeZone) zone.clone();
 sharedZone = false;
 }
 return zone;
 }

 /**
 * Returns the time zone (without cloning).
 */
 TimeZone getZone() {
 return zone;
 }

 /**
 * Sets the sharedZone flag to {@code shared}.
 */
 void setZoneShared(boolean shared) {
 sharedZone = shared;
 }

 /**
 * Specifies 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 (non-lenient) interpretation, such dates will cause an exception to be
 * thrown. The default is lenient.
 *
 * @param lenient {@code true} if the lenient mode is to be turned
 * on; {@code false} if it is to be turned off.
 * @see #isLenient()
 * @see java.text.DateFormat#setLenient
 */
 public void setLenient(boolean lenient)
 {
 this.lenient = lenient;
 }

 /**
 * Tells whether date/time interpretation is to be lenient.
 *
 * @return {@code true} if the interpretation mode of this calendar is lenient;
 * {@code false} otherwise.
 * @see #setLenient(boolean)
 */
 public boolean isLenient()
 {
 return lenient;
 }

 /**
 * Sets what the first day of the week is; e.g., {@code SUNDAY} in the U.S.,
 * {@code MONDAY} in France.
 *
 * @param value the given first day of the week.
 * @see #getFirstDayOfWeek()
 * @see #getMinimalDaysInFirstWeek()
 */
 public void setFirstDayOfWeek(int value)
 {
 if (firstDayOfWeek == value) {
 return;
 }
 firstDayOfWeek = value;
 invalidateWeekFields();
 }

 /**
 * Gets what the first day of the week is; e.g., {@code SUNDAY} in the U.S.,
 * {@code MONDAY} in France.
 *
 * @return the first day of the week.
 * @see #setFirstDayOfWeek(int)
 * @see #getMinimalDaysInFirstWeek()
 */
 public int getFirstDayOfWeek()
 {
 return firstDayOfWeek;
 }

 /**
 * 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 this 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.
 * @see #getMinimalDaysInFirstWeek()
 */
 public void setMinimalDaysInFirstWeek(int value)
 {
 if (minimalDaysInFirstWeek == value) {
 return;
 }
 minimalDaysInFirstWeek = value;
 invalidateWeekFields();
 }

 /**
 * 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, this method returns 1. If
 * the minimal days required must be a full week, this method
 * returns 7.
 *
 * @return the minimal days required in the first week of the year.
 * @see #setMinimalDaysInFirstWeek(int)
 */
 public int getMinimalDaysInFirstWeek()
 {
 return minimalDaysInFirstWeek;
 }

 /**
 * Returns whether this {@code Calendar} supports week dates.
 *
 * The default implementation of this method returns {@code false}.
 *
 * @return {@code true} if this {@code Calendar} supports week dates;
 * {@code false} otherwise.
 * @see #getWeekYear()
 * @see #setWeekDate(int,int,int)
 * @see #getWeeksInWeekYear()
 * @since 1.7
 */
 public boolean isWeekDateSupported() {
 return false;
 }

 /**
 * Returns the week year represented by this {@code Calendar}. The
 * week year is in sync with the week cycle. The {@linkplain
 * #getFirstDayOfWeek() first day of the first week} is the first
 * day of the week year.
 *
 * The default implementation of this method throws an
 * {@link UnsupportedOperationException}.
 *
 * @return the week year of this {@code Calendar}
 * @throws UnsupportedOperationException
 * if any week year numbering isn't supported
 * in this {@code Calendar}.
 * @see #isWeekDateSupported()
 * @see #getFirstDayOfWeek()
 * @see #getMinimalDaysInFirstWeek()
 * @since 1.7
 */
 public int getWeekYear() {
 throw new UnsupportedOperationException();
 }

 /**
 * Sets the date of this {@code Calendar} with the given date
 * specifiers - week year, week of year, and day of week.
 *
 * Unlike the {@code set} method, all of the calendar fields
 * and {@code time} values are calculated upon return.
 *
 * If {@code weekOfYear} is out of the valid week-of-year range
 * in {@code weekYear}, the {@code weekYear} and {@code
 * weekOfYear} values are adjusted in lenient mode, or an {@code
 * IllegalArgumentException} is thrown in non-lenient mode.
 *
 * The default implementation of this method throws an
 * {@code UnsupportedOperationException}.
 *
 * @param weekYear the week year
 * @param weekOfYear the week number based on {@code weekYear}
 * @param dayOfWeek the day of week value: one of the constants
 * for the {@link #DAY_OF_WEEK} field: {@link
 * #SUNDAY}, ..., {@link #SATURDAY}.
 * @throws IllegalArgumentException
 * if any of the given date specifiers is invalid
 * or any of the calendar fields are inconsistent
 * with the given date specifiers in non-lenient mode
 * @throws UnsupportedOperationException
 * if any week year numbering isn't supported in this
 * {@code Calendar}.
 * @see #isWeekDateSupported()
 * @see #getFirstDayOfWeek()
 * @see #getMinimalDaysInFirstWeek()
 * @since 1.7
 */
 public void setWeekDate(int weekYear, int weekOfYear, int dayOfWeek) {
 throw new UnsupportedOperationException();
 }

 /**
 * Returns the number of weeks in the week year represented by this
 * {@code Calendar}.
 *
 * The default implementation of this method throws an
 * {@code UnsupportedOperationException}.
 *
 * @return the number of weeks in the week year.
 * @throws UnsupportedOperationException
 * if any week year numbering isn't supported in this
 * {@code Calendar}.
 * @see #WEEK_OF_YEAR
 * @see #isWeekDateSupported()
 * @see #getWeekYear()
 * @see #getActualMaximum(int)
 * @since 1.7
 */
 public int getWeeksInWeekYear() {
 throw new UnsupportedOperationException();
 }

 /**
 * Returns the minimum value for the given calendar field of this
 * {@code Calendar} instance. The minimum value is defined as
 * the smallest value returned by the {@link #get(int) get} method
 * for any possible time value. The minimum value depends on
 * calendar system specific parameters of the instance.
 *
 * @param field the calendar field.
 * @return the minimum value for the given calendar field.
 * @see #getMaximum(int)
 * @see #getGreatestMinimum(int)
 * @see #getLeastMaximum(int)
 * @see #getActualMinimum(int)
 * @see #getActualMaximum(int)
 */
 public abstract int getMinimum(int field);

 /**
 * Returns the maximum value for the given calendar field of this
 * {@code Calendar} instance. The maximum value is defined as
 * the largest value returned by the {@link #get(int) get} method
 * for any possible time value. The maximum value depends on
 * calendar system specific parameters of the instance.
 *
 * @param field the calendar field.
 * @return the maximum value for the given calendar field.
 * @see #getMinimum(int)
 * @see #getGreatestMinimum(int)
 * @see #getLeastMaximum(int)
 * @see #getActualMinimum(int)
 * @see #getActualMaximum(int)
 */
 public abstract int getMaximum(int field);

 /**
 * Returns the highest minimum value for the given calendar field
 * of this {@code Calendar} instance. The highest minimum
 * value is defined as the largest value returned by {@link
 * #getActualMinimum(int)} for any possible time value. The
 * greatest minimum value depends on calendar system specific
 * parameters of the instance.
 *
 * @param field the calendar field.
 * @return the highest minimum value for the given calendar field.
 * @see #getMinimum(int)
 * @see #getMaximum(int)
 * @see #getLeastMaximum(int)
 * @see #getActualMinimum(int)
 * @see #getActualMaximum(int)
 */
 public abstract int getGreatestMinimum(int field);

 /**
 * Returns the lowest maximum value for the given calendar field
 * of this {@code Calendar} instance. The lowest maximum
 * value is defined as the smallest value returned by {@link
 * #getActualMaximum(int)} for any possible time value. The least
 * maximum value depends on calendar system specific parameters of
 * the instance. For example, a {@code Calendar} for the
 * Gregorian calendar system returns 28 for the
 * {@code DAY_OF_MONTH} field, because the 28th is the last
 * day of the shortest month of this calendar, February in a
 * common year.
 *
 * @param field the calendar field.
 * @return the lowest maximum value for the given calendar field.
 * @see #getMinimum(int)
 * @see #getMaximum(int)
 * @see #getGreatestMinimum(int)
 * @see #getActualMinimum(int)
 * @see #getActualMaximum(int)
 */
 public abstract int getLeastMaximum(int field);

 /**
 * Returns the minimum value that the specified calendar field
 * could have, given the time value of this {@code Calendar}.
 *
 * The default implementation of this method uses an iterative
 * algorithm to determine the actual minimum value for the
 * calendar field. Subclasses should, if possible, override this
 * with a more efficient implementation - in many cases, they can
 * simply return {@code getMinimum()}.
 *
 * @param field the calendar field
 * @return the minimum of the given calendar field for the time
 * value of this {@code Calendar}
 * @see #getMinimum(int)
 * @see #getMaximum(int)
 * @see #getGreatestMinimum(int)
 * @see #getLeastMaximum(int)
 * @see #getActualMaximum(int)
 * @since 1.2
 */
 public int getActualMinimum(int field) {
 int fieldValue = getGreatestMinimum(field);
 int endValue = getMinimum(field);

 // if we know that the minimum value is always the same, just return it
 if (fieldValue == endValue) {
 return fieldValue;
 }

 // clone the calendar so we don't mess with the real one, and set it to
 // accept anything for the field values
 Calendar work = (Calendar)this.clone();
 work.setLenient(true);

 // now try each value from getLeastMaximum() to getMaximum() one by one until
 // we get a value that normalizes to another value. The last value that
 // normalizes to itself is the actual minimum for the current date
 int result = fieldValue;

 do {
 work.set(field, fieldValue);
 if (work.get(field) != fieldValue) {
 break;
 } else {
 result = fieldValue;
 fieldValue--;
 }
 } while (fieldValue >= endValue);

 return result;
 }

 /**
 * Returns the maximum value that the specified calendar field
 * could have, given the time value of this
 * {@code Calendar}. For example, the actual maximum value of
 * the {@code MONTH} field is 12 in some years, and 13 in
 * other years in the Hebrew calendar system.
 *
 * The default implementation of this method uses an iterative
 * algorithm to determine the actual maximum value for the
 * calendar field. Subclasses should, if possible, override this
 * with a more efficient implementation.
 *
 * @param field the calendar field
 * @return the maximum of the given calendar field for the time
 * value of this {@code Calendar}
 * @see #getMinimum(int)
 * @see #getMaximum(int)
 * @see #getGreatestMinimum(int)
 * @see #getLeastMaximum(int)
 * @see #getActualMinimum(int)
 * @since 1.2
 */
 public int getActualMaximum(int field) {
 int fieldValue = getLeastMaximum(field);
 int endValue = getMaximum(field);

 // if we know that the maximum value is always the same, just return it.
 if (fieldValue == endValue) {
 return fieldValue;
 }

 // clone the calendar so we don't mess with the real one, and set it to
 // accept anything for the field values.
 Calendar work = (Calendar)this.clone();
 work.setLenient(true);

 // if we're counting weeks, set the day of the week to Sunday. We know the
 // last week of a month or year will contain the first day of the week.
 if (field == WEEK_OF_YEAR || field == WEEK_OF_MONTH) {
 work.set(DAY_OF_WEEK, firstDayOfWeek);
 }

 // now try each value from getLeastMaximum() to getMaximum() one by one until
 // we get a value that normalizes to another value. The last value that
 // normalizes to itself is the actual maximum for the current date
 int result = fieldValue;

 do {
 work.set(field, fieldValue);
 if (work.get(field) != fieldValue) {
 break;
 } else {
 result = fieldValue;
 fieldValue++;
 }
 } while (fieldValue <= endValue);

 return result;
 }

 /**
 * Creates and returns a copy of this object.
 *
 * @return a copy of this object.
 */
 @Override
 public Object clone()
 {
 try {
 Calendar other = (Calendar) super.clone();

 other.fields = new int[FIELD_COUNT];
 other.isSet = new boolean[FIELD_COUNT];
 other.stamp = new int[FIELD_COUNT];
 for (int i = 0; i < FIELD_COUNT; i++) {
 other.fields[i] = fields[i];
 other.stamp[i] = stamp[i];
 other.isSet[i] = isSet[i];
 }
 if (!sharedZone) {
 other.zone = (TimeZone) zone.clone();
 }
 return other;
 }
 catch (CloneNotSupportedException e) {
 // this shouldn't happen, since we are Cloneable
 throw new InternalError(e);
 }
 }

 private static final String[] FIELD_NAME = {
 "ERA", "YEAR", "MONTH", "WEEK_OF_YEAR", "WEEK_OF_MONTH", "DAY_OF_MONTH",
 "DAY_OF_YEAR", "DAY_OF_WEEK", "DAY_OF_WEEK_IN_MONTH", "AM_PM", "HOUR",
 "HOUR_OF_DAY", "MINUTE", "SECOND", "MILLISECOND", "ZONE_OFFSET",
 "DST_OFFSET"
 };

 /**
 * Returns the name of the specified calendar field.
 *
 * @param field the calendar field
 * @return the calendar field name
 * @throws IndexOutOfBoundsException if {@code field} is negative,
 * equal to or greater than {@code FIELD_COUNT}.
 */
 static String getFieldName(int field) {
 return FIELD_NAME[field];
 }

 /**
 * 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 {@code null}.
 *
 * @return a string representation of this calendar.
 */
 @Override
 public String toString() {
 // NOTE: BuddhistCalendar.toString() interprets the string
 // produced by this method so that the Gregorian year number
 // is substituted by its B.E. year value. It relies on
 // "...,YEAR=<year>,..." or "...,YEAR=?,...".
 StringBuilder buffer = new StringBuilder(800);
 buffer.append(getClass().getName()).append('[');
 appendValue(buffer, "time", isTimeSet, time);
 buffer.append(",areFieldsSet=").append(areFieldsSet);
 buffer.append(",areAllFieldsSet=").append(areAllFieldsSet);
 buffer.append(",lenient=").append(lenient);
 buffer.append(",zone=").append(zone);
 appendValue(buffer, ",firstDayOfWeek", true, (long) firstDayOfWeek);
 appendValue(buffer, ",minimalDaysInFirstWeek", true, (long) minimalDaysInFirstWeek);
 for (int i = 0; i < FIELD_COUNT; ++i) {
 buffer.append(',');
 appendValue(buffer, FIELD_NAME[i], isSet(i), (long) fields[i]);
 }
 buffer.append(']');
 return buffer.toString();
 }

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

 private static void appendValue(StringBuilder sb, String item, boolean valid, long value) {
 sb.append(item).append('=');
 if (valid) {
 sb.append(value);
 } else {
 sb.append('?');
 }
 }

 /**
 * Both firstDayOfWeek and minimalDaysInFirstWeek are locale-dependent.
 * 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.
 * @param desiredLocale the given locale.
 */
 private void setWeekCountData(Locale desiredLocale)
 {
 /* try to get the Locale data from the cache */
 int[] data = cachedLocaleData.get(desiredLocale);
 if (data == null) { /* cache miss */
 data = new int[2];
 data[0] = CalendarDataUtility.retrieveFirstDayOfWeek(desiredLocale);
 data[1] = CalendarDataUtility.retrieveMinimalDaysInFirstWeek(desiredLocale);
 cachedLocaleData.putIfAbsent(desiredLocale, data);
 }
 firstDayOfWeek = data[0];
 minimalDaysInFirstWeek = data[1];
 }

 /**
 * Recomputes the time and updates the status fields isTimeSet
 * and areFieldsSet. Callers should check isTimeSet and only
 * call this method if isTimeSet is false.
 */
 private void updateTime() {
 computeTime();
 // The areFieldsSet and areAllFieldsSet values are no longer
 // controlled here (as of 1.5).
 isTimeSet = true;
 }

 private int compareTo(long t) {
 return Long.compare(getMillisOf(this), t);
 }

 private static long getMillisOf(Calendar calendar) {
 if (calendar.isTimeSet) {
 return calendar.time;
 }
 Calendar cal = (Calendar) calendar.clone();
 cal.setLenient(true);
 return cal.getTimeInMillis();
 }

 /**
 * Adjusts the stamp[] values before nextStamp overflow. nextStamp
 * is set to the next stamp value upon the return.
 */
 private void adjustStamp() {
 int max = MINIMUM_USER_STAMP;
 int newStamp = MINIMUM_USER_STAMP;

 for (;;) {
 int min = Integer.MAX_VALUE;
 for (int v : stamp) {
 if (v >= newStamp && min > v) {
 min = v;
 }
 if (max < v) {
 max = v;
 }
 }
 if (max != min && min == Integer.MAX_VALUE) {
 break;
 }
 for (int i = 0; i < stamp.length; i++) {
 if (stamp[i] == min) {
 stamp[i] = newStamp;
 }
 }
 newStamp++;
 if (min == max) {
 break;
 }
 }
 nextStamp = newStamp;
 }

 /**
 * Sets the WEEK_OF_MONTH and WEEK_OF_YEAR fields to new values with the
 * new parameter value if they have been calculated internally.
 */
 private void invalidateWeekFields()
 {
 if (stamp[WEEK_OF_MONTH] != COMPUTED &&
 stamp[WEEK_OF_YEAR] != COMPUTED) {
 return;
 }

 // We have to check the new values of these fields after changing
 // firstDayOfWeek and/or minimalDaysInFirstWeek. If the field values
 // have been changed, then set the new values. (4822110)
 Calendar cal = (Calendar) clone();
 cal.setLenient(true);
 cal.clear(WEEK_OF_MONTH);
 cal.clear(WEEK_OF_YEAR);

 if (stamp[WEEK_OF_MONTH] == COMPUTED) {
 int weekOfMonth = cal.get(WEEK_OF_MONTH);
 if (fields[WEEK_OF_MONTH] != weekOfMonth) {
 fields[WEEK_OF_MONTH] = weekOfMonth;
 }
 }

 if (stamp[WEEK_OF_YEAR] == COMPUTED) {
 int weekOfYear = cal.get(WEEK_OF_YEAR);
 if (fields[WEEK_OF_YEAR] != weekOfYear) {
 fields[WEEK_OF_YEAR] = weekOfYear;
 }
 }
 }

 /**
 * Save the state of this object to a stream (i.e., serialize it).
 *
 * Ideally, {@code Calendar} would only write out its state data and
 * the current time, and not write any field data out, such as
 * {@code fields[]}, {@code isTimeSet}, {@code areFieldsSet},
 * and {@code isSet[]}. {@code 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, {@code nextStamp} can be
 * removed from the serialization stream; this will probably happen in the
 * near future.
 */
 @java.io.Serial
 private synchronized void writeObject(ObjectOutputStream stream)
 throws IOException
 {
 // Try to compute the time correctly, for the future (stream
 // version 2) in which we don't write out fields[] or isSet[].
 if (!isTimeSet) {
 try {
 updateTime();
 }
 catch (IllegalArgumentException e) {}
 }

 // If this Calendar has a ZoneInfo, save it and set a
 // SimpleTimeZone equivalent (as a single DST schedule) for
 // backward compatibility.
 TimeZone savedZone = null;
 if (zone instanceof ZoneInfo) {
 SimpleTimeZone stz = ((ZoneInfo)zone).getLastRuleInstance();
 if (stz == null) {
 stz = new SimpleTimeZone(zone.getRawOffset(), zone.getID());
 }
 savedZone = zone;
 zone = stz;
 }

 // Write out the 1.1 FCS object.
 stream.defaultWriteObject();

 // Write out the ZoneInfo object
 // 4802409: we write out even if it is null, a temporary workaround
 // the real fix for bug 4844924 in corba-iiop
 stream.writeObject(savedZone);
 if (savedZone != null) {
 zone = savedZone;
 }
 }

 @SuppressWarnings("removal")
 private static class CalendarAccessControlContext {
 private static final AccessControlContext INSTANCE;
 static {
 RuntimePermission perm = new RuntimePermission("accessClassInPackage.sun.util.calendar");
 PermissionCollection perms = perm.newPermissionCollection();
 perms.add(perm);
 INSTANCE = new AccessControlContext(new ProtectionDomain[] {
 new ProtectionDomain(null, perms)
 });
 }
 private CalendarAccessControlContext() {
 }
 }

 /**
 * Reconstitutes this object from a stream (i.e., deserialize it).
 */
 @SuppressWarnings("removal")
 @java.io.Serial
 private void readObject(ObjectInputStream stream)
 throws IOException, ClassNotFoundException
 {
 final ObjectInputStream input = stream;
 input.defaultReadObject();

 stamp = new int[FIELD_COUNT];

 // Starting with version 2 (not implemented yet), we expect that
 // fields[], isSet[], isTimeSet, and areFieldsSet may not be
 // streamed out anymore. We expect 'time' to be correct.
 if (serialVersionOnStream >= 2)
 {
 isTimeSet = true;
 if (fields == null) {
 fields = new int[FIELD_COUNT];
 }
 if (isSet == null) {
 isSet = new boolean[FIELD_COUNT];
 }
 }
 else if (serialVersionOnStream >= 0)
 {
 for (int i=0; i<FIELD_COUNT; ++i) {
 stamp[i] = isSet[i] ? COMPUTED : UNSET;
 }
 }

 serialVersionOnStream = currentSerialVersion;

 // If there's a ZoneInfo object, use it for zone.
 ZoneInfo zi = null;
 try {
 zi = AccessController.doPrivileged(
 new PrivilegedExceptionAction<>() {
 @Override
 public ZoneInfo run() throws Exception {
 return (ZoneInfo) input.readObject();
 }
 },
 CalendarAccessControlContext.INSTANCE);
 } catch (PrivilegedActionException pae) {
 Exception e = pae.getException();
 if (!(e instanceof OptionalDataException)) {
 if (e instanceof RuntimeException) {
 throw (RuntimeException) e;
 } else if (e instanceof IOException) {
 throw (IOException) e;
 } else if (e instanceof ClassNotFoundException) {
 throw (ClassNotFoundException) e;
 }
 throw new RuntimeException(e);
 }
 }
 if (zi != null) {
 zone = zi;
 }

 // If the deserialized object has a SimpleTimeZone, try to
 // replace it with a ZoneInfo equivalent (as of 1.4) in order
 // to be compatible with the SimpleTimeZone-based
 // implementation as much as possible.
 if (zone instanceof SimpleTimeZone) {
 String id = zone.getID();
 TimeZone tz = TimeZone.getTimeZone(id);
 if (tz != null && tz.hasSameRules(zone) && tz.getID().equals(id)) {
 zone = tz;
 }
 }
 }

 /**
 * Converts this object to an {@link Instant}.
 * 
 * The conversion creates an {@code Instant} that represents the
 * same point on the time-line as this {@code Calendar}.
 *
 * @return the instant representing the same point on the time-line
 * @since 1.8
 */
 public final Instant toInstant() {
 return Instant.ofEpochMilli(getTimeInMillis());
 }
}

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