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/*
* Copyright (c) 1996, 2026, 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
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* 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).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* (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.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"><em>Epoch</em></a>, January 1, 1970
* 00:00:00.000 GMT (Gregorian).
*
* <p>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}.
*
* <p>
* 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>
*
* <p>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>
*
* <p>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.
* Unless otherwise specified, any {@code Calendar} method containing the
* parameter {@code int field} will throw an {@code ArrayIndexOutOfBoundsException}
* if the specified field is out of range ({@code field} < 0 ||
* {@code field} >= {@link #FIELD_COUNT}).
*
* <h3>Leniency</h3>
*
* <p>{@code Calendar} has two modes for interpreting the calendar
* fields, <em>lenient</em> and <em>non-lenient</em>. 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.
*
* <p>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" {@linkplain Locale##def_locale_extension
* Unicode extensions}, 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.
*
* <p>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><i>n</i></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.
*
* <p><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.
*
* <p><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>
*
* <p>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.
*
* <p>
* <strong>Note:</strong> 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>
*
* <p>
* 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()}.
*
* <p><strong>{@code set(f, value)}</strong> 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.</p>
*
* <p><em>Example</em>: 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.</p>
*
* <p><strong>{@code add(f, delta)}</strong> adds {@code delta}
* to field {@code f}. This is equivalent to calling <code>set(f,
* get(f) + delta)</code> with two adjustments:</p>
*
* <blockquote>
* <p><strong>Add rule 1</strong>. 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.</p>
*
* <p><strong>Add rule 2</strong>. 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.</p>
* </blockquote>
*
* <p>In addition, unlike {@code set()}, {@code add()} forces
* an immediate recomputation of the calendar's milliseconds and all
* fields.</p>
*
* <p><em>Example</em>: Consider a {@code GregorianCalendar}
* originally set to August 31, 1999. Calling <code>add(Calendar.MONTH,
* 13)</code> sets the calendar to September 30, 2000. <strong>Add rule
* 1</strong> 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}, <strong>add rule 2</strong> 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}. In leap years, the adjustment accounts
* for the leap day in February to ensure the day of month is valid
* for the year.</p>
*
* <p><strong>{@code roll(f, delta)}</strong> adds
* {@code delta} to field {@code f} without changing larger
* fields. This is equivalent to calling {@code add(f, delta)} with
* the following adjustment:</p>
*
* <blockquote>
* <p><strong>Roll rule</strong>. 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}.</p>
* </blockquote>
*
* <p><em>Example</em>: See {@link java.util.GregorianCalendar#roll(int, int)}.
*
* <p><strong>Usage model</strong>. 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.</p>
*
* @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. If the calendar is non-lenient, this field takes values
* {@code SUNDAY}, {@code MONDAY}, {@code TUESDAY}, {@code WEDNESDAY},
* {@code THURSDAY}, {@code FRIDAY}, and {@code SATURDAY}. Otherwise, any
* int values are accepted and normalized to one of the previously
* mentioned values.
*
* @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 <em>not</em> 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.
* <p>
* 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.
* <p>
* 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><b>0</b> or not present on stream</dt>
* <dd>
* JDK 1.1.5 or earlier.
* </dd>
* <dt><b>1</b></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>