Class GregorianCalendar
- All Implemented Interfaces:
Serializable
,Cloneable
,Comparable<Calendar>
- Direct Known Subclasses:
BuddhistCalendar
,JapaneseCalendar
,TaiwanCalendar
GregorianCalendar
is a concrete subclass of
Calendar
and provides the standard calendar used by most of the world.
The standard (Gregorian) calendar has 2 eras, BC and AD.
This implementation handles a single discontinuity, which corresponds by
default to the date the Gregorian calendar was instituted (October 15, 1582
in some countries, later in others). The cutover date may be changed by the
caller by calling setGregorianChange()
.
Historically, in those countries which adopted the Gregorian calendar first,
October 4, 1582 was thus followed by October 15, 1582. This calendar models
this correctly. Before the Gregorian cutover, GregorianCalendar
implements the Julian calendar. The only difference between the Gregorian
and the Julian calendar is the leap year rule. The Julian calendar specifies
leap years every four years, whereas the Gregorian calendar omits century
years which are not divisible by 400.
GregorianCalendar
implements proleptic Gregorian and
Julian calendars. That is, dates are computed by extrapolating the current
rules indefinitely far backward and forward in time. As a result,
GregorianCalendar
may be used for all years to generate
meaningful and consistent results. However, dates obtained using
GregorianCalendar
are historically accurate only from March 1, 4
AD onward, when modern Julian calendar rules were adopted. Before this date,
leap year rules were applied irregularly, and before 45 BC the Julian
calendar did not even exist.
Prior to the institution of the Gregorian calendar, New Year's Day was March 25. To avoid confusion, this calendar always uses January 1. A manual adjustment may be made if desired for dates that are prior to the Gregorian changeover and which fall between January 1 and March 24.
Values calculated for the WEEK_OF_YEAR
field range from 1 to
53. Week 1 for a year is the earliest seven day period starting on
getFirstDayOfWeek()
that contains at least
getMinimalDaysInFirstWeek()
days from that year. It thus
depends on the values of getMinimalDaysInFirstWeek()
,
getFirstDayOfWeek()
, and the day of the week of January 1.
Weeks between week 1 of one year and week 1 of the following year are
numbered sequentially from 2 to 52 or 53 (as needed).
For example, January 1, 1998 was a Thursday. If
getFirstDayOfWeek()
is MONDAY
and
getMinimalDaysInFirstWeek()
is 4 (these are the values
reflecting ISO 8601 and many national standards), then week 1 of 1998 starts
on December 29, 1997, and ends on January 4, 1998. If, however,
getFirstDayOfWeek()
is SUNDAY
, then week 1 of 1998
starts on January 4, 1998, and ends on January 10, 1998; the first three days
of 1998 then are part of week 53 of 1997.
Values calculated for the WEEK_OF_MONTH
field range from 0 or
1 to 4 or 5. Week 1 of a month (the days with WEEK_OF_MONTH =
1
) is the earliest set of at least
getMinimalDaysInFirstWeek()
contiguous days in that month,
ending on the day before getFirstDayOfWeek()
. Unlike
week 1 of a year, week 1 of a month may be shorter than 7 days, need
not start on getFirstDayOfWeek()
, and will not include days of
the previous month. Days of a month before week 1 have a
WEEK_OF_MONTH
of 0.
For example, if getFirstDayOfWeek()
is SUNDAY
and getMinimalDaysInFirstWeek()
is 4, then the first week of
January 1998 is Sunday, January 4 through Saturday, January 10. These days
have a WEEK_OF_MONTH
of 1. Thursday, January 1 through
Saturday, January 3 have a WEEK_OF_MONTH
of 0. If
getMinimalDaysInFirstWeek()
is changed to 3, then January 1
through January 3 have a WEEK_OF_MONTH
of 1.
Example:
// get the supported ids for GMT-08:00 (Pacific Standard Time) String[] ids = TimeZone.getAvailableIDs(-8 * 60 * 60 * 1000); // if no ids were returned, something is wrong. get out. if (ids.length == 0) System.exit(0); // begin output System.out.println("Current Time"); // create a Pacific Standard Time time zone SimpleTimeZone pdt = new SimpleTimeZone(-8 * 60 * 60 * 1000, ids[0]); // set up rules for daylight savings time pdt.setStartRule(Calendar.MARCH, 2, Calendar.SUNDAY, 2 * 60 * 60 * 1000); pdt.setEndRule(Calendar.NOVEMBER, 1, Calendar.SUNDAY, 2 * 60 * 60 * 1000); // create a GregorianCalendar with the Pacific Daylight time zone // and the current date and time Calendar calendar = new GregorianCalendar(pdt); Date trialTime = new Date(); calendar.setTime(trialTime); // print out a bunch of interesting things System.out.println("ERA: " + calendar.get(Calendar.ERA)); System.out.println("YEAR: " + calendar.get(Calendar.YEAR)); System.out.println("MONTH: " + calendar.get(Calendar.MONTH)); System.out.println("WEEK_OF_YEAR: " + calendar.get(Calendar.WEEK_OF_YEAR)); System.out.println("WEEK_OF_MONTH: " + calendar.get(Calendar.WEEK_OF_MONTH)); System.out.println("DATE: " + calendar.get(Calendar.DATE)); System.out.println("DAY_OF_MONTH: " + calendar.get(Calendar.DAY_OF_MONTH)); System.out.println("DAY_OF_YEAR: " + calendar.get(Calendar.DAY_OF_YEAR)); System.out.println("DAY_OF_WEEK: " + calendar.get(Calendar.DAY_OF_WEEK)); System.out.println("DAY_OF_WEEK_IN_MONTH: " + calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH)); System.out.println("AM_PM: " + calendar.get(Calendar.AM_PM)); System.out.println("HOUR: " + calendar.get(Calendar.HOUR)); System.out.println("HOUR_OF_DAY: " + calendar.get(Calendar.HOUR_OF_DAY)); System.out.println("MINUTE: " + calendar.get(Calendar.MINUTE)); System.out.println("SECOND: " + calendar.get(Calendar.SECOND)); System.out.println("MILLISECOND: " + calendar.get(Calendar.MILLISECOND)); System.out.println("ZONE_OFFSET: " + (calendar.get(Calendar.ZONE_OFFSET)/(60*60*1000))); System.out.println("DST_OFFSET: " + (calendar.get(Calendar.DST_OFFSET)/(60*60*1000))); System.out.println("Current Time, with hour reset to 3"); calendar.clear(Calendar.HOUR_OF_DAY); // so doesn't override calendar.set(Calendar.HOUR, 3); System.out.println("ERA: " + calendar.get(Calendar.ERA)); System.out.println("YEAR: " + calendar.get(Calendar.YEAR)); System.out.println("MONTH: " + calendar.get(Calendar.MONTH)); System.out.println("WEEK_OF_YEAR: " + calendar.get(Calendar.WEEK_OF_YEAR)); System.out.println("WEEK_OF_MONTH: " + calendar.get(Calendar.WEEK_OF_MONTH)); System.out.println("DATE: " + calendar.get(Calendar.DATE)); System.out.println("DAY_OF_MONTH: " + calendar.get(Calendar.DAY_OF_MONTH)); System.out.println("DAY_OF_YEAR: " + calendar.get(Calendar.DAY_OF_YEAR)); System.out.println("DAY_OF_WEEK: " + calendar.get(Calendar.DAY_OF_WEEK)); System.out.println("DAY_OF_WEEK_IN_MONTH: " + calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH)); System.out.println("AM_PM: " + calendar.get(Calendar.AM_PM)); System.out.println("HOUR: " + calendar.get(Calendar.HOUR)); System.out.println("HOUR_OF_DAY: " + calendar.get(Calendar.HOUR_OF_DAY)); System.out.println("MINUTE: " + calendar.get(Calendar.MINUTE)); System.out.println("SECOND: " + calendar.get(Calendar.SECOND)); System.out.println("MILLISECOND: " + calendar.get(Calendar.MILLISECOND)); System.out.println("ZONE_OFFSET: " + (calendar.get(Calendar.ZONE_OFFSET)/(60*60*1000))); // in hours System.out.println("DST_OFFSET: " + (calendar.get(Calendar.DST_OFFSET)/(60*60*1000))); // in hours
GregorianCalendar usually should be instantiated using
Calendar.getInstance(ULocale)
passing in a ULocale
with the tag "@calendar=gregorian"
.
- Author:
- Deborah Goldsmith, Mark Davis, Chen-Lieh Huang, Alan Liu
- See Also:
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Nested Class Summary
Nested classes/interfaces inherited from class com.ibm.icu.util.Calendar
Calendar.FormatConfiguration, Calendar.WeekData
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Field Summary
FieldsModifier and TypeFieldDescriptionstatic final int
Value of theERA
field indicating the common era (Anno Domini), also known as CE.static final int
Value of theERA
field indicating the period before the common era (before Christ), also known as BCE.protected boolean
Used by handleComputeJulianDay() and handleComputeMonthStart().protected boolean
Used by handleComputeJulianDay() and handleComputeMonthStart().Fields inherited from class com.ibm.icu.util.Calendar
AM, AM_PM, APRIL, AUGUST, BASE_FIELD_COUNT, DATE, DAY_OF_MONTH, DAY_OF_WEEK, DAY_OF_WEEK_IN_MONTH, DAY_OF_YEAR, DECEMBER, DOW_LOCAL, DST_OFFSET, EPOCH_JULIAN_DAY, ERA, EXTENDED_YEAR, FEBRUARY, FRIDAY, GREATEST_MINIMUM, HOUR, HOUR_OF_DAY, INTERNALLY_SET, IS_LEAP_MONTH, JAN_1_1_JULIAN_DAY, JANUARY, JULIAN_DAY, JULY, JUNE, LEAST_MAXIMUM, MARCH, MAX_DATE, MAX_FIELD_COUNT, MAX_JULIAN, MAX_MILLIS, MAXIMUM, MAY, MILLISECOND, MILLISECONDS_IN_DAY, MIN_DATE, MIN_JULIAN, MIN_MILLIS, MINIMUM, MINIMUM_USER_STAMP, MINUTE, MONDAY, MONTH, NOVEMBER, OCTOBER, ONE_DAY, ONE_HOUR, ONE_MINUTE, ONE_SECOND, ONE_WEEK, PM, RESOLVE_REMAP, SATURDAY, SECOND, SEPTEMBER, SUNDAY, THURSDAY, TUESDAY, UNDECIMBER, UNSET, WALLTIME_FIRST, WALLTIME_LAST, WALLTIME_NEXT_VALID, WEDNESDAY, WEEK_OF_MONTH, WEEK_OF_YEAR, WEEKDAY, WEEKEND, WEEKEND_CEASE, WEEKEND_ONSET, YEAR, YEAR_WOY, ZONE_OFFSET
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Constructor Summary
ConstructorsConstructorDescriptionConstructs a default GregorianCalendar using the current time in the default time zone with the defaultFORMAT
locale.GregorianCalendar
(int year, int month, int date) Constructs a GregorianCalendar with the given date set in the default time zone with the defaultFORMAT
locale.GregorianCalendar
(int year, int month, int date, int hour, int minute) Constructs a GregorianCalendar with the given date and time set for the default time zone with the defaultFORMAT
locale.GregorianCalendar
(int year, int month, int date, int hour, int minute, int second) Constructs a GregorianCalendar with the given date and time set for the default time zone with the defaultFORMAT
locale.GregorianCalendar
(TimeZone zone) Constructs a GregorianCalendar based on the current time in the given time zone with the defaultFORMAT
locale.GregorianCalendar
(TimeZone zone, ULocale locale) Constructs a GregorianCalendar based on the current time in the given time zone with the given locale.GregorianCalendar
(TimeZone zone, Locale aLocale) Constructs a GregorianCalendar based on the current time in the given time zone with the given locale.GregorianCalendar
(ULocale locale) Constructs a GregorianCalendar based on the current time in the default time zone with the given locale.GregorianCalendar
(Locale aLocale) Constructs a GregorianCalendar based on the current time in the default time zone with the given locale. -
Method Summary
Modifier and TypeMethodDescriptionint
getActualMaximum
(int field) Return the maximum value that this field could have, given the current date.int
getActualMinimum
(int field) Return the minimum value that this field could have, given the current date.final Date
Gets the Gregorian Calendar change date.getType()
Returns the calendar type name string for this Calendar object.protected void
handleComputeFields
(int julianDay) Override Calendar to compute several fields specific to the hybrid Gregorian-Julian calendar system.protected int
handleComputeJulianDay
(int bestField) Subclasses may override this.protected int
handleComputeMonthStart
(int eyear, int month, boolean useMonth) Return JD of start of given month/yearprotected int
Returns the extended year defined by the current fields.protected int
handleGetLimit
(int field, int limitType) Subclass API for defining limits of different types.protected int
handleGetMonthLength
(int extendedYear, int month) Returns the number of days in the given month of the given extended year of this calendar system.protected int
handleGetYearLength
(int eyear) Returns the number of days in the given extended year of this calendar system.int
hashCode()
Override hashCode.boolean
isEquivalentTo
(Calendar other) Returns true if the given Calendar object is equivalent to this one.boolean
isLeapYear
(int year) Determines if the given year is a leap year.void
roll
(int field, int amount) Roll a field by a signed amount.void
setGregorianChange
(Date date) Sets the GregorianCalendar change date.Methods inherited from class com.ibm.icu.util.Calendar
add, after, before, clear, clear, clone, compareTo, complete, computeFields, computeGregorianFields, computeGregorianMonthStart, computeJulianDay, computeMillisInDay, computeMillisInDayLong, computeTime, computeZoneOffset, computeZoneOffset, equals, fieldDifference, fieldName, floorDivide, floorDivide, floorDivide, floorDivide, get, getAvailableLocales, getAvailableULocales, getDateAtTimePattern, getDateTimeFormat, getDateTimeFormat, getDateTimePattern, getDayOfWeekType, getDefaultDayInMonth, getDefaultMonthInYear, getDisplayName, getDisplayName, getFieldCount, getFieldResolutionTable, getFirstDayOfWeek, getGreatestMinimum, getGregorianDayOfMonth, getGregorianDayOfYear, getGregorianMonth, getGregorianYear, getInstance, getInstance, getInstance, getInstance, getInstance, getInstance, getKeywordValuesForLocale, getLeastMaximum, getLimit, getLocale, getMaximum, getMinimalDaysInFirstWeek, getMinimum, getRelatedYear, getRepeatedWallTimeOption, getSkippedWallTimeOption, getStamp, getTime, getTimeInMillis, getTimeZone, getWeekData, getWeekDataForRegion, getWeekendTransition, gregorianMonthLength, gregorianPreviousMonthLength, handleCreateFields, handleGetDateFormat, handleGetDateFormat, handleGetDateFormat, handleGetDateFormat, haveDefaultCentury, internalGet, internalGet, internalGetTimeInMillis, internalSet, isGregorianLeapYear, isLenient, isSet, isWeekend, isWeekend, julianDayToDayOfWeek, julianDayToMillis, millisToJulianDay, newerField, newestStamp, pinField, prepareGetActual, resolveFields, roll, set, set, set, set, setFirstDayOfWeek, setLenient, setMinimalDaysInFirstWeek, setRelatedYear, setRepeatedWallTimeOption, setSkippedWallTimeOption, setTime, setTimeInMillis, setTimeZone, setWeekData, toString, validateField, validateField, validateFields, weekNumber, weekNumber
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Field Details
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BC
public static final int BCValue of theERA
field indicating the period before the common era (before Christ), also known as BCE. The sequence of years at the transition fromBC
toAD
is ..., 2 BC, 1 BC, 1 AD, 2 AD,...- See Also:
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AD
public static final int ADValue of theERA
field indicating the common era (Anno Domini), also known as CE. The sequence of years at the transition fromBC
toAD
is ..., 2 BC, 1 BC, 1 AD, 2 AD,...- See Also:
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isGregorian
protected transient boolean isGregorianUsed by handleComputeJulianDay() and handleComputeMonthStart(). -
invertGregorian
protected transient boolean invertGregorianUsed by handleComputeJulianDay() and handleComputeMonthStart().
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Constructor Details
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GregorianCalendar
public GregorianCalendar()Constructs a default GregorianCalendar using the current time in the default time zone with the defaultFORMAT
locale.- See Also:
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GregorianCalendar
Constructs a GregorianCalendar based on the current time in the given time zone with the defaultFORMAT
locale.- Parameters:
zone
- the given time zone.- See Also:
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GregorianCalendar
Constructs a GregorianCalendar based on the current time in the default time zone with the given locale.- Parameters:
aLocale
- the given locale.
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GregorianCalendar
Constructs a GregorianCalendar based on the current time in the default time zone with the given locale.- Parameters:
locale
- the given ulocale.
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GregorianCalendar
Constructs a GregorianCalendar based on the current time in the given time zone with the given locale.- Parameters:
zone
- the given time zone.aLocale
- the given locale.
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GregorianCalendar
Constructs a GregorianCalendar based on the current time in the given time zone with the given locale.- Parameters:
zone
- the given time zone.locale
- the given ulocale.
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GregorianCalendar
public GregorianCalendar(int year, int month, int date) Constructs a GregorianCalendar with the given date set in the default time zone with the defaultFORMAT
locale.- Parameters:
year
- the value used to set the YEAR time field in the calendar.month
- the value used to set the MONTH time field in the calendar. Month value is 0-based. e.g., 0 for January.date
- the value used to set the DATE time field in the calendar.- See Also:
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GregorianCalendar
public GregorianCalendar(int year, int month, int date, int hour, int minute) Constructs a GregorianCalendar with the given date and time set for the default time zone with the defaultFORMAT
locale.- Parameters:
year
- the value used to set the YEAR time field in the calendar.month
- the value used to set the MONTH time field in the calendar. Month value is 0-based. e.g., 0 for January.date
- the value used to set the DATE time field in the calendar.hour
- the value used to set the HOUR_OF_DAY time field in the calendar.minute
- the value used to set the MINUTE time field in the calendar.- See Also:
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GregorianCalendar
public GregorianCalendar(int year, int month, int date, int hour, int minute, int second) Constructs a GregorianCalendar with the given date and time set for the default time zone with the defaultFORMAT
locale.- Parameters:
year
- the value used to set the YEAR time field in the calendar.month
- the value used to set the MONTH time field in the calendar. Month value is 0-based. e.g., 0 for January.date
- the value used to set the DATE time field in the calendar.hour
- the value used to set the HOUR_OF_DAY time field in the calendar.minute
- the value used to set the MINUTE time field in the calendar.second
- the value used to set the SECOND time field in the calendar.- See Also:
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Method Details
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handleGetLimit
protected int handleGetLimit(int field, int limitType) Description copied from class:Calendar
Subclass API for defining limits of different types. Subclasses must implement this method to return limits for the following fields:ERA YEAR MONTH WEEK_OF_YEAR WEEK_OF_MONTH DAY_OF_MONTH DAY_OF_YEAR DAY_OF_WEEK_IN_MONTH YEAR_WOY EXTENDED_YEAR
- Specified by:
handleGetLimit
in classCalendar
- Parameters:
field
- one of the above field numberslimitType
- one ofMINIMUM
,GREATEST_MINIMUM
,LEAST_MAXIMUM
, orMAXIMUM
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setGregorianChange
Sets the GregorianCalendar change date. This is the point when the switch from Julian dates to Gregorian dates occurred. Default is October 15, 1582. Previous to this, dates will be in the Julian calendar.To obtain a pure Julian calendar, set the change date to
Date(Long.MAX_VALUE)
. To obtain a pure Gregorian calendar, set the change date toDate(Long.MIN_VALUE)
.- Parameters:
date
- the given Gregorian cutover date.
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getGregorianChange
Gets the Gregorian Calendar change date. This is the point when the switch from Julian dates to Gregorian dates occurred. Default is October 15, 1582. Previous to this, dates will be in the Julian calendar.- Returns:
- the Gregorian cutover date for this calendar.
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isLeapYear
public boolean isLeapYear(int year) Determines if the given year is a leap year. Returns true if the given year is a leap year.- Parameters:
year
- the given year.- Returns:
- true if the given year is a leap year; false otherwise.
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isEquivalentTo
Returns true if the given Calendar object is equivalent to this one. Calendar override.- Overrides:
isEquivalentTo
in classCalendar
- Parameters:
other
- the Calendar to be compared with this Calendar
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hashCode
public int hashCode()Override hashCode. Generates the hash code for the GregorianCalendar object -
roll
public void roll(int field, int amount) Roll a field by a signed amount. -
getActualMinimum
public int getActualMinimum(int field) Return the minimum value that this field could have, given the current date. For the Gregorian calendar, this is the same as getMinimum() and getGreatestMinimum().- Overrides:
getActualMinimum
in classCalendar
- Parameters:
field
- the field whose actual minimum value is desired.- Returns:
- the minimum of the given field for the current date of this calendar
- See Also:
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getActualMaximum
public int getActualMaximum(int field) Return the maximum value that this field could have, given the current date. For example, with the date "Feb 3, 1997" and the DAY_OF_MONTH field, the actual maximum would be 28; for "Feb 3, 1996" it s 29. Similarly for a Hebrew calendar, for some years the actual maximum for MONTH is 12, and for others 13.- Overrides:
getActualMaximum
in classCalendar
- Parameters:
field
- the field whose maximum is desired- Returns:
- the maximum of the given field for the current date of this calendar
- See Also:
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handleGetMonthLength
protected int handleGetMonthLength(int extendedYear, int month) Description copied from class:Calendar
Returns the number of days in the given month of the given extended year of this calendar system. Subclasses should override this method if they can provide a more correct or more efficient implementation than the default implementation in Calendar.- Overrides:
handleGetMonthLength
in classCalendar
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handleGetYearLength
protected int handleGetYearLength(int eyear) Description copied from class:Calendar
Returns the number of days in the given extended year of this calendar system. Subclasses should override this method if they can provide a more correct or more efficient implementation than the default implementation in Calendar.- Overrides:
handleGetYearLength
in classCalendar
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handleComputeFields
protected void handleComputeFields(int julianDay) Override Calendar to compute several fields specific to the hybrid Gregorian-Julian calendar system. These are:- ERA
- YEAR
- MONTH
- DAY_OF_MONTH
- DAY_OF_YEAR
- EXTENDED_YEAR
- Overrides:
handleComputeFields
in classCalendar
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handleGetExtendedYear
protected int handleGetExtendedYear()Description copied from class:Calendar
Returns the extended year defined by the current fields. This will use the EXTENDED_YEAR field or the YEAR and supra-year fields (such as ERA) specific to the calendar system, depending on which set of fields is newer.- Specified by:
handleGetExtendedYear
in classCalendar
- Returns:
- the extended year
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handleComputeJulianDay
protected int handleComputeJulianDay(int bestField) Description copied from class:Calendar
Subclasses may override this. This method calls handleGetMonthLength() to obtain the calendar-specific month length.- Overrides:
handleComputeJulianDay
in classCalendar
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handleComputeMonthStart
protected int handleComputeMonthStart(int eyear, int month, boolean useMonth) Return JD of start of given month/year- Specified by:
handleComputeMonthStart
in classCalendar
- Parameters:
eyear
- the extended yearmonth
- the zero-based month, or 0 if useMonth is falseuseMonth
- if false, compute the day before the first day of the given year, otherwise, compute the day before the first day of the given month- Returns:
- the Julian day number of the day before the first day of the given month and year
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getType
Returns the calendar type name string for this Calendar object. The returned string is the legacy ICU calendar attribute value, for example, "gregorian" or "japanese".See type="old type name" for the calendar attribute of locale IDs at http://www.unicode.org/reports/tr35/#Key_Type_Definitions
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