- All Implemented Interfaces:
Serializable,Cloneable,Comparable<Calendar>
- Direct Known Subclasses:
GregorianCalendar
Calendar class is an abstract class that provides methods
for converting between a specific instant in time and a set of calendar fields such as YEAR, MONTH,
DAY_OF_MONTH, 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 Epoch, 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 protected.
Like other locale-sensitive classes, Calendar provides a
class method, getInstance, for getting a generally useful
object of this type. Calendar's getInstance method
returns a Calendar object whose
calendar fields have been initialized with the current date and time:
Calendar rightNow = Calendar.getInstance();
A 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).
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 MONTH ==
JANUARY for all calendars. Other values are defined by the
concrete subclass, such as ERA. See individual field
documentation and subclass documentation for details.
Getting and Setting Calendar Field Values
The calendar field values can be set by calling the set
methods. Any field values set in a 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
get, getTimeInMillis, getTime,
add and roll involves such calculation.
Leniency
Calendar has two modes for interpreting the calendar
fields, lenient and non-lenient. When a
Calendar is in lenient mode, it accepts a wider range of
calendar field values than it produces. When a Calendar
recomputes calendar field values for return by get(), all of
the calendar fields are normalized. For example, a lenient
GregorianCalendar interprets MONTH == JANUARY,
DAY_OF_MONTH == 32 as February 1.
When a Calendar is in non-lenient mode, it throws an
exception if there is any inconsistency in its calendar fields. For
example, a GregorianCalendar always produces
DAY_OF_MONTH values between 1 and the length of the month. A
non-lenient GregorianCalendar throws an exception upon
calculating its time or calendar field values if any out-of-range field
value has been set.
First Week
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 Calendar is constructed. If the designated
locale contains "fw" and/or "rg"
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.
When setting or getting the WEEK_OF_MONTH or
WEEK_OF_YEAR fields, Calendar must determine the
first week of the month or year as a reference point. The first week of a
month or year is defined as the earliest seven day period beginning on
getFirstDayOfWeek() and containing at least
getMinimalDaysInFirstWeek() days of that month or year. Weeks
numbered ..., -1, 0 precede the first week; weeks numbered 2, 3,... follow
it. Note that the normalized numbering returned by get() may be
different. For example, a specific Calendar subclass may
designate the week before week 1 of a year as week n of
the previous year.
Calendar Fields Resolution
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).Calendar will resolve
calendar field values to determine the date and time in the
following way.
If there is any conflict in calendar field values,
Calendar gives priorities to calendar fields that have been set
more recently. 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.
For the time of day fields: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
HOUR_OF_DAY AM_PM + HOUR
If there are any calendar fields whose values haven't been set in the selected
field combination, Calendar uses their default values. The default
value of each field may vary by concrete calendar systems. For example, in
GregorianCalendar, the default of a field is the same as that
of the start of the Epoch: i.e., YEAR = 1970, MONTH =
JANUARY, DAY_OF_MONTH = 1, etc.
Note: There are certain possible ambiguities in interpretation of certain singular times, which are resolved in the following ways:
- 23:59 is the last minute of the day and 00:00 is the first minute of the next day. Thus, 23:59 on Dec 31, 1999 < 00:00 on Jan 1, 2000 < 00:01 on Jan 1, 2000.
- Although historically not precise, midnight also belongs to "am", and noon belongs to "pm", so on the same day, 12:00 am (midnight) < 12:01 am, and 12:00 pm (noon) < 12:01 pm
The date or time format strings are not part of the definition of a
calendar, as those must be modifiable or overridable by the user at
runtime. Use DateFormat
to format dates.
Field Manipulation
The calendar fields can be changed using three methods:set(), add(), and roll().
set(f, value) changes calendar field
f to value. In addition, it sets an
internal member variable to indicate that calendar field f has
been changed. Although calendar field f is changed immediately,
the calendar's time value in milliseconds is not recomputed until the next call to
get(), getTime(), getTimeInMillis(),
add(), or roll() is made. Thus, multiple calls to
set() do not trigger multiple, unnecessary
computations. As a result of changing a calendar field using
set(), other calendar fields may also change, depending on the
calendar field, the calendar field value, and the calendar system. In addition,
get(f) will not necessarily return value set by
the call to the set method
after the calendar fields have been recomputed. The specifics are determined by
the concrete calendar class.
Example: Consider a GregorianCalendar
originally set to August 31, 1999. Calling set(Calendar.MONTH,
Calendar.SEPTEMBER) sets the date to September 31,
1999. This is a temporary internal representation that resolves to
October 1, 1999 if getTime() is then called. However, a
call to set(Calendar.DAY_OF_MONTH, 30) before the call to
getTime() sets the date to September 30, 1999, since
no recomputation occurs after set() itself.
add(f, delta) adds delta
to field f. This is equivalent to calling set(f,
get(f) + delta) with two adjustments:
Add rule 1. The value of field
fafter the call minus the value of fieldfbefore the call isdelta, modulo any overflow that has occurred in fieldf. 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
fis 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.HOURis a smaller field thanDAY_OF_MONTH. No adjustment is made to smaller fields that are not expected to be invariant. The calendar system determines what fields are expected to be invariant.
In addition, unlike set(), add() forces
an immediate recomputation of the calendar's milliseconds and all
fields.
Example: Consider a GregorianCalendar
originally set to August 31, 1999. Calling add(Calendar.MONTH,
13) sets the calendar to September 30, 2000. Add rule
1 sets the MONTH field to September, since
adding 13 months to August gives September of the next year. Since
DAY_OF_MONTH cannot be 31 in September in a
GregorianCalendar, add rule 2 sets the
DAY_OF_MONTH to 30, the closest possible value. Although
it is a smaller field, DAY_OF_WEEK is not adjusted by
rule 2, since it is expected to change when the month changes in a
GregorianCalendar.
roll(f, delta) adds
delta to field f without changing larger
fields. This is equivalent to calling add(f, delta) with
the following adjustment:
Roll rule. Larger fields are unchanged after the call. A larger field represents a larger unit of time.
DAY_OF_MONTHis a larger field thanHOUR.
Example: See GregorianCalendar.roll(int, int).
Usage model. To motivate the behavior of
add() and roll(), consider a user interface
component with increment and decrement buttons for the month, day, and
year, and an underlying GregorianCalendar. If the
interface reads January 31, 1999 and the user presses the month
increment button, what should it read? If the underlying
implementation uses set(), it might read March 3, 1999. A
better result would be February 28, 1999. Furthermore, if the user
presses the month increment button again, it should read March 31,
1999, not March 28, 1999. By saving the original date and using either
add() or roll(), depending on whether larger
fields should be affected, the user interface can behave as most users
will intuitively expect.
- Since:
- 1.1
- See Also:
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic classCalendar.Builderis used for creating aCalendarfrom various date-time parameters. -
Field Summary
FieldsModifier and TypeFieldDescriptionstatic final intA style specifier forgetDisplayNamesindicating names in all styles, such as "January" and "Jan".static final intValue of theAM_PMfield indicating the period of the day from midnight to just before noon.static final intField number forgetandsetindicating whether theHOURis before or after noon.static final intValue of theMONTHfield indicating the fourth month of the year in the Gregorian and Julian calendars.protected booleanTrue iffields[]are in sync with the currently set time.static final intValue of theMONTHfield indicating the eighth month of the year in the Gregorian and Julian calendars.static final intField number forgetandsetindicating the day of the month.static final intField number forgetandsetindicating the day of the month.static final intField number forgetandsetindicating the day of the week.static final intField number forgetandsetindicating the ordinal number of the day of the week within the current month.static final intField number forgetandsetindicating the day number within the current year.static final intValue of theMONTHfield indicating the twelfth month of the year in the Gregorian and Julian calendars.static final intField number forgetandsetindicating the daylight saving offset in milliseconds.static final intField number forgetandsetindicating the era, e.g., AD or BC in the Julian calendar.static final intValue of theMONTHfield indicating the second month of the year in the Gregorian and Julian calendars.static final intThe number of distinct fields recognized bygetandset.protected int[]The calendar field values for the currently set time for this calendar.static final intValue of theDAY_OF_WEEKfield indicating Friday.static final intField number forgetandsetindicating the hour of the morning or afternoon.static final intField number forgetandsetindicating the hour of the day.protected boolean[]The flags which tell if a specified calendar field for the calendar is set.protected booleanTrue if then the value oftimeis valid.static final intValue of theMONTHfield indicating the first month of the year in the Gregorian and Julian calendars.static final intValue of theMONTHfield indicating the seventh month of the year in the Gregorian and Julian calendars.static final intValue of theMONTHfield indicating the sixth month of the year in the Gregorian and Julian calendars.static final intstatic final intA style specifier forgetDisplayNameandgetDisplayNamesindicating a long name used for format.static final intA style specifier forgetDisplayNameandgetDisplayNamesindicating a long name used independently, such as a month name as calendar headers.static final intValue of theMONTHfield indicating the third month of the year in the Gregorian and Julian calendars.static final intValue of theMONTHfield indicating the fifth month of the year in the Gregorian and Julian calendars.static final intField number forgetandsetindicating the millisecond within the second.static final intField number forgetandsetindicating the minute within the hour.static final intValue of theDAY_OF_WEEKfield indicating Monday.static final intField number forgetandsetindicating the month.static final intA style specifier forgetDisplayNameandgetDisplayNamesindicating a narrow name used for format.static final intA style specifier forgetDisplayNameandgetDisplayNamesindicating a narrow name independently.static final intValue of theMONTHfield indicating the eleventh month of the year in the Gregorian and Julian calendars.static final intValue of theMONTHfield indicating the tenth month of the year in the Gregorian and Julian calendars.static final intValue of theAM_PMfield indicating the period of the day from noon to just before midnight.static final intValue of theDAY_OF_WEEKfield indicating Saturday.static final intField number forgetandsetindicating the second within the minute.static final intValue of theMONTHfield indicating the ninth month of the year in the Gregorian and Julian calendars.static final intstatic final intA style specifier forgetDisplayNameandgetDisplayNamesindicating a short name used for format.static final intA style specifier forgetDisplayNameandgetDisplayNamesindicating a short name used independently, such as a month abbreviation as calendar headers.static final intValue of theDAY_OF_WEEKfield indicating Sunday.static final intValue of theDAY_OF_WEEKfield indicating Thursday.protected longThe currently set time for this calendar, expressed in milliseconds after January 1, 1970, 0:00:00 GMT.static final intValue of theDAY_OF_WEEKfield indicating Tuesday.static final intValue of theMONTHfield indicating the thirteenth month of the year.static final intValue of theDAY_OF_WEEKfield indicating Wednesday.static final intField number forgetandsetindicating the week number within the current month.static final intField number forgetandsetindicating the week number within the current year.static final intField number forgetandsetindicating the year.static final intField number forgetandsetindicating the raw offset from GMT in milliseconds. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionabstract voidadd(int field, int amount) Adds or subtracts the specified amount of time to the given calendar field, based on the calendar's rules.booleanReturns whether thisCalendarrepresents a time after the time represented by the specifiedObject.booleanReturns whether thisCalendarrepresents a time before the time represented by the specifiedObject.final voidclear()Sets all the calendar field values and the time value (millisecond offset from the Epoch) of thisCalendarundefined.final voidclear(int field) Sets the given calendar field value and the time value (millisecond offset from the Epoch) of thisCalendarundefined.clone()Creates and returns a copy of this object.intCompares the time values (millisecond offsets from the Epoch) represented by twoCalendarobjects.protected voidcomplete()Fills in any unset fields in the calendar fields.protected abstract voidprotected abstract voidbooleanCompares thisCalendarto the specifiedObject.intget(int field) Returns the value of the given calendar field.intgetActualMaximum(int field) Returns the maximum value that the specified calendar field could have, given the time value of thisCalendar.intgetActualMinimum(int field) Returns the minimum value that the specified calendar field could have, given the time value of thisCalendar.Returns an unmodifiableSetcontaining all calendar types supported byCalendarin the runtime environment.static Locale[]Returns an array of all locales for which thegetInstancemethods of this class can return localized instances.Returns the calendar type of thisCalendar.getDisplayName(int field, int style, Locale locale) Returns the string representation of the calendarfieldvalue in the givenstyleandlocale.getDisplayNames(int field, int style, Locale locale) Returns aMapcontaining all names of the calendarfieldin the givenstyleandlocaleand their corresponding field values.intGets what the first day of the week is; e.g.,SUNDAYin the U.S.,MONDAYin France.abstract intgetGreatestMinimum(int field) Returns the highest minimum value for the given calendar field of thisCalendarinstance.static CalendarGets a calendar using the default time zone and locale.static CalendargetInstance(Locale aLocale) Gets a calendar using the default time zone and specified locale.static CalendargetInstance(TimeZone zone) Gets a calendar using the specified time zone and default locale.static CalendargetInstance(TimeZone zone, Locale aLocale) Gets a calendar with the specified time zone and locale.abstract intgetLeastMaximum(int field) Returns the lowest maximum value for the given calendar field of thisCalendarinstance.abstract intgetMaximum(int field) Returns the maximum value for the given calendar field of thisCalendarinstance.intGets 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.abstract intgetMinimum(int field) Returns the minimum value for the given calendar field of thisCalendarinstance.final DategetTime()longReturns this Calendar's time value in milliseconds.Gets the time zone.intReturns the number of weeks in the week year represented by thisCalendar.intReturns the week year represented by thisCalendar.inthashCode()Returns a hash code for this calendar.protected final intinternalGet(int field) Returns the value of the given calendar field.booleanTells whether date/time interpretation is to be lenient.final booleanisSet(int field) Determines if the given calendar field has a value set, including cases that the value has been set by internal fields calculations triggered by agetmethod call.booleanReturns whether thisCalendarsupports week dates.abstract voidroll(int field, boolean up) Adds or subtracts (up/down) a single unit of time on the given time field without changing larger fields.voidroll(int field, int amount) Adds the specified (signed) amount to the specified calendar field without changing larger fields.voidset(int field, int value) Sets the given calendar field to the given value.final voidset(int year, int month, int date) Sets the values for the calendar fieldsYEAR,MONTH, andDAY_OF_MONTH.final voidset(int year, int month, int date, int hourOfDay, int minute) Sets the values for the calendar fieldsYEAR,MONTH,DAY_OF_MONTH,HOUR_OF_DAY, andMINUTE.final voidset(int year, int month, int date, int hourOfDay, int minute, int second) Sets the values for the fieldsYEAR,MONTH,DAY_OF_MONTH,HOUR_OF_DAY,MINUTE, andSECOND.voidsetFirstDayOfWeek(int value) Sets what the first day of the week is; e.g.,SUNDAYin the U.S.,MONDAYin France.voidsetLenient(boolean lenient) Specifies whether or not date/time interpretation is to be lenient.voidsetMinimalDaysInFirstWeek(int value) 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.final voidSets this Calendar's time with the givenDate.voidsetTimeInMillis(long millis) Sets this Calendar's current time from the given long value.voidsetTimeZone(TimeZone value) Sets the time zone with the given time zone value.voidsetWeekDate(int weekYear, int weekOfYear, int dayOfWeek) Sets the date of thisCalendarwith the given date specifiers - week year, week of year, and day of week.final InstantConverts this object to anInstant.toString()Return a string representation of this calendar.
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Field Details
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ERA
public static final int ERAField number forgetandsetindicating the era, e.g., AD or BC in the Julian calendar. This is a calendar-specific value; see subclass documentation. -
YEAR
public static final int YEARField number forgetandsetindicating the year. This is a calendar-specific value; see subclass documentation.- See Also:
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MONTH
public static final int MONTHField number forgetandsetindicating the month. This is a calendar-specific value. The first month of the year in the Gregorian and Julian calendars isJANUARYwhich is 0; the last depends on the number of months in a year. -
WEEK_OF_YEAR
public static final int WEEK_OF_YEARField number forgetandsetindicating the week number within the current year. The first week of the year, as defined bygetFirstDayOfWeek()andgetMinimalDaysInFirstWeek(), has value 1. Subclasses define the value ofWEEK_OF_YEARfor days before the first week of the year. -
WEEK_OF_MONTH
public static final int WEEK_OF_MONTHField number forgetandsetindicating the week number within the current month. The first week of the month, as defined bygetFirstDayOfWeek()andgetMinimalDaysInFirstWeek(), has value 1. Subclasses define the value ofWEEK_OF_MONTHfor days before the first week of the month. -
DATE
public static final int DATEField number forgetandsetindicating the day of the month. This is a synonym forDAY_OF_MONTH. The first day of the month has value 1.- See Also:
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DAY_OF_MONTH
public static final int DAY_OF_MONTHField number forgetandsetindicating the day of the month. This is a synonym forDATE. The first day of the month has value 1.- See Also:
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DAY_OF_YEAR
public static final int DAY_OF_YEARField number forgetandsetindicating the day number within the current year. The first day of the year has value 1.- See Also:
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DAY_OF_WEEK
public static final int DAY_OF_WEEKField number forgetandsetindicating the day of the week. This field takes valuesSUNDAY,MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY, andSATURDAY. -
DAY_OF_WEEK_IN_MONTH
public static final int DAY_OF_WEEK_IN_MONTHField number forgetandsetindicating the ordinal number of the day of the week within the current month. Together with theDAY_OF_WEEKfield, this uniquely specifies a day within a month. UnlikeWEEK_OF_MONTHandWEEK_OF_YEAR, this field's value does not depend ongetFirstDayOfWeek()orgetMinimalDaysInFirstWeek().DAY_OF_MONTH 1through7always correspond toDAY_OF_WEEK_IN_MONTH 1;8through14correspond toDAY_OF_WEEK_IN_MONTH 2, and so on.DAY_OF_WEEK_IN_MONTH 0indicates the week beforeDAY_OF_WEEK_IN_MONTH 1. Negative values count back from the end of the month, so the last Sunday of a month is specified asDAY_OF_WEEK = SUNDAY, DAY_OF_WEEK_IN_MONTH = -1. Because negative values count backward they will usually be aligned differently within the month than positive values. For example, if a month has 31 days,DAY_OF_WEEK_IN_MONTH -1will overlapDAY_OF_WEEK_IN_MONTH 5and the end of4.- See Also:
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AM_PM
public static final int AM_PMField number forgetandsetindicating whether theHOURis before or after noon. E.g., at 10:04:15.250 PM theAM_PMisPM.- See Also:
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HOUR
public static final int HOURField number forgetandsetindicating the hour of the morning or afternoon.HOURis 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 theHOURis 10.- See Also:
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HOUR_OF_DAY
public static final int HOUR_OF_DAYField number forgetandsetindicating the hour of the day.HOUR_OF_DAYis used for the 24-hour clock. E.g., at 10:04:15.250 PM theHOUR_OF_DAYis 22.- See Also:
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MINUTE
public static final int MINUTEField number forgetandsetindicating the minute within the hour. E.g., at 10:04:15.250 PM theMINUTEis 4.- See Also:
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SECOND
public static final int SECONDField number forgetandsetindicating the second within the minute. E.g., at 10:04:15.250 PM theSECONDis 15.- See Also:
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MILLISECOND
public static final int MILLISECONDField number forgetandsetindicating the millisecond within the second. E.g., at 10:04:15.250 PM theMILLISECONDis 250.- See Also:
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ZONE_OFFSET
public static final int ZONE_OFFSETField number forgetandsetindicating the raw offset from GMT in milliseconds.This field reflects the correct GMT offset value of the time zone of this
Calendarif theTimeZoneimplementation subclass supports historical GMT offset changes.- See Also:
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DST_OFFSET
public static final int DST_OFFSETField number forgetandsetindicating the daylight saving offset in milliseconds.This field reflects the correct daylight saving offset value of the time zone of this
Calendarif theTimeZoneimplementation subclass supports historical Daylight Saving Time schedule changes.- See Also:
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FIELD_COUNT
public static final int FIELD_COUNTThe number of distinct fields recognized bygetandset. Field numbers range from0..FIELD_COUNT-1.- See Also:
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SUNDAY
public static final int SUNDAYValue of theDAY_OF_WEEKfield indicating Sunday.- See Also:
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MONDAY
public static final int MONDAYValue of theDAY_OF_WEEKfield indicating Monday.- See Also:
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TUESDAY
public static final int TUESDAYValue of theDAY_OF_WEEKfield indicating Tuesday.- See Also:
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WEDNESDAY
public static final int WEDNESDAYValue of theDAY_OF_WEEKfield indicating Wednesday.- See Also:
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THURSDAY
public static final int THURSDAYValue of theDAY_OF_WEEKfield indicating Thursday.- See Also:
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FRIDAY
public static final int FRIDAYValue of theDAY_OF_WEEKfield indicating Friday.- See Also:
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SATURDAY
public static final int SATURDAYValue of theDAY_OF_WEEKfield indicating Saturday.- See Also:
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JANUARY
public static final int JANUARYValue of theMONTHfield indicating the first month of the year in the Gregorian and Julian calendars.- See Also:
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FEBRUARY
public static final int FEBRUARYValue of theMONTHfield indicating the second month of the year in the Gregorian and Julian calendars.- See Also:
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MARCH
public static final int MARCHValue of theMONTHfield indicating the third month of the year in the Gregorian and Julian calendars.- See Also:
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APRIL
public static final int APRILValue of theMONTHfield indicating the fourth month of the year in the Gregorian and Julian calendars.- See Also:
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MAY
public static final int MAYValue of theMONTHfield indicating the fifth month of the year in the Gregorian and Julian calendars.- See Also:
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JUNE
public static final int JUNEValue of theMONTHfield indicating the sixth month of the year in the Gregorian and Julian calendars.- See Also:
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JULY
public static final int JULYValue of theMONTHfield indicating the seventh month of the year in the Gregorian and Julian calendars.- See Also:
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AUGUST
public static final int AUGUSTValue of theMONTHfield indicating the eighth month of the year in the Gregorian and Julian calendars.- See Also:
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SEPTEMBER
public static final int SEPTEMBERValue of theMONTHfield indicating the ninth month of the year in the Gregorian and Julian calendars.- See Also:
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OCTOBER
public static final int OCTOBERValue of theMONTHfield indicating the tenth month of the year in the Gregorian and Julian calendars.- See Also:
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NOVEMBER
public static final int NOVEMBERValue of theMONTHfield indicating the eleventh month of the year in the Gregorian and Julian calendars.- See Also:
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DECEMBER
public static final int DECEMBERValue of theMONTHfield indicating the twelfth month of the year in the Gregorian and Julian calendars.- See Also:
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UNDECIMBER
public static final int UNDECIMBERValue of theMONTHfield indicating the thirteenth month of the year. AlthoughGregorianCalendardoes not use this value, lunar calendars do.- See Also:
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AM
public static final int AMValue of theAM_PMfield indicating the period of the day from midnight to just before noon.- See Also:
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PM
public static final int PMValue of theAM_PMfield indicating the period of the day from noon to just before midnight.- See Also:
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ALL_STYLES
public static final int ALL_STYLESA style specifier forgetDisplayNamesindicating names in all styles, such as "January" and "Jan".- Since:
- 1.6
- See Also:
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SHORT
public static final int SHORT- Since:
- 1.6
- See Also:
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LONG
public static final int LONG- Since:
- 1.6
- See Also:
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NARROW_FORMAT
public static final int NARROW_FORMATA style specifier forgetDisplayNameandgetDisplayNamesindicating a narrow name used for format. Narrow names are typically single character strings, such as "M" for Monday.- Since:
- 1.8
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NARROW_STANDALONE
public static final int NARROW_STANDALONEA style specifier forgetDisplayNameandgetDisplayNamesindicating a narrow name independently. Narrow names are typically single character strings, such as "M" for Monday.- Since:
- 1.8
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SHORT_FORMAT
public static final int SHORT_FORMATA style specifier forgetDisplayNameandgetDisplayNamesindicating a short name used for format.- Since:
- 1.8
- See Also:
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LONG_FORMAT
public static final int LONG_FORMATA style specifier forgetDisplayNameandgetDisplayNamesindicating a long name used for format.- Since:
- 1.8
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SHORT_STANDALONE
public static final int SHORT_STANDALONEA style specifier forgetDisplayNameandgetDisplayNamesindicating a short name used independently, such as a month abbreviation as calendar headers.- Since:
- 1.8
- See Also:
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LONG_STANDALONE
public static final int LONG_STANDALONEA style specifier forgetDisplayNameandgetDisplayNamesindicating a long name used independently, such as a month name as calendar headers.- Since:
- 1.8
- See Also:
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fields
protected int[] fieldsThe calendar field values for the currently set time for this calendar. This is an array ofFIELD_COUNTintegers, with index valuesERAthroughDST_OFFSET. -
isSet
protected boolean[] isSetThe 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 ofFIELD_COUNTbooleans, with index valuesERAthroughDST_OFFSET. -
time
protected long timeThe currently set time for this calendar, expressed in milliseconds after January 1, 1970, 0:00:00 GMT.- See Also:
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isTimeSet
protected boolean isTimeSetTrue if then the value oftimeis valid. The time is made invalid by a change to an item offield[].- See Also:
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areFieldsSet
protected boolean areFieldsSetTrue iffields[]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 oftime.
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Constructor Details
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Calendar
protected Calendar()Constructs a Calendar with the default time zone and the defaultFORMATlocale.- See Also:
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Calendar
Constructs a calendar with the specified time zone and locale.- Parameters:
zone- the time zone to useaLocale- the locale for the week data
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Method Details
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getInstance
Gets a calendar using the default time zone and locale. TheCalendarreturned is based on the current time in the default time zone with the defaultFORMATlocale.If the locale contains the time zone with "tz" Unicode extension, that time zone is used instead.
- Returns:
- a Calendar.
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getInstance
Gets a calendar using the specified time zone and default locale. TheCalendarreturned is based on the current time in the given time zone with the defaultFORMATlocale.- Parameters:
zone- the time zone to use- Returns:
- a Calendar.
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getInstance
Gets a calendar using the default time zone and specified locale. TheCalendarreturned is based on the current time in the default time zone with the given locale.If the locale contains the time zone with "tz" Unicode extension, that time zone is used instead.
- Parameters:
aLocale- the locale for the week data- Returns:
- a Calendar.
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getInstance
Gets a calendar with the specified time zone and locale. TheCalendarreturned is based on the current time in the given time zone with the given locale.- Parameters:
zone- the time zone to useaLocale- the locale for the week data- Returns:
- a Calendar.
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getAvailableLocales
Returns an array of all locales for which thegetInstancemethods of this class can return localized instances. The array returned must contain at least aLocaleinstance equal toLocale.US.- Returns:
- An array of locales for which localized
Calendarinstances are available.
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computeTime
protected abstract void computeTime()- See Also:
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computeFields
protected abstract void computeFields()Converts the current millisecond time valuetimeto calendar field values infields[]. 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 thecomplete()method.- See Also:
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getTime
- Returns:
- a
Daterepresenting the time value. - See Also:
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setTime
Sets this Calendar's time with the givenDate.Note: Calling
setTime()withDate(Long.MAX_VALUE)orDate(Long.MIN_VALUE)may yield incorrect field values fromget().- Parameters:
date- the given Date.- Throws:
NullPointerException- ifdateisnull- See Also:
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getTimeInMillis
public long getTimeInMillis()Returns this Calendar's time value in milliseconds.- Returns:
- the current time as UTC milliseconds from the epoch.
- See Also:
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setTimeInMillis
public void setTimeInMillis(long millis) Sets this Calendar's current time from the given long value.- Parameters:
millis- the new time in UTC milliseconds from the epoch.- See Also:
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get
public int get(int field) 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 thecomplete()method, which process is calendar system dependent.- Parameters:
field- the given calendar field.- Returns:
- the value for the given calendar field.
- Throws:
ArrayIndexOutOfBoundsException- if the specified field is out of range (field < 0 || field >= FIELD_COUNT).- See Also:
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internalGet
protected final int internalGet(int field) Returns the value of the given calendar field. This method does not involve normalization or validation of the field value.- Parameters:
field- the given calendar field.- Returns:
- the value for the given calendar field.
- See Also:
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set
public void set(int field, int value) Sets the given calendar field to the given value. The value is not interpreted by this method regardless of the leniency mode.- Parameters:
field- the given calendar field.value- the value to be set for the given calendar field.- Throws:
ArrayIndexOutOfBoundsException- if the specified field is out of range (field < 0 || field >= FIELD_COUNT). in non-lenient mode.- See Also:
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set
public final void set(int year, int month, int date) Sets the values for the calendar fieldsYEAR,MONTH, andDAY_OF_MONTH. Previous values of other calendar fields are retained. If this is not desired, callclear()first.- Parameters:
year- the value used to set theYEARcalendar field.month- the value used to set theMONTHcalendar field. Month value is 0-based. e.g., 0 for January.date- the value used to set theDAY_OF_MONTHcalendar field.- See Also:
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set
public final void set(int year, int month, int date, int hourOfDay, int minute) Sets the values for the calendar fieldsYEAR,MONTH,DAY_OF_MONTH,HOUR_OF_DAY, andMINUTE. Previous values of other fields are retained. If this is not desired, callclear()first.- Parameters:
year- the value used to set theYEARcalendar field.month- the value used to set theMONTHcalendar field. Month value is 0-based. e.g., 0 for January.date- the value used to set theDAY_OF_MONTHcalendar field.hourOfDay- the value used to set theHOUR_OF_DAYcalendar field.minute- the value used to set theMINUTEcalendar field.- See Also:
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set
public final void set(int year, int month, int date, int hourOfDay, int minute, int second) Sets the values for the fieldsYEAR,MONTH,DAY_OF_MONTH,HOUR_OF_DAY,MINUTE, andSECOND. Previous values of other fields are retained. If this is not desired, callclear()first.- Parameters:
year- the value used to set theYEARcalendar field.month- the value used to set theMONTHcalendar field. Month value is 0-based. e.g., 0 for January.date- the value used to set theDAY_OF_MONTHcalendar field.hourOfDay- the value used to set theHOUR_OF_DAYcalendar field.minute- the value used to set theMINUTEcalendar field.second- the value used to set theSECONDcalendar field.- See Also:
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clear
public final void clear()Sets all the calendar field values and the time value (millisecond offset from the Epoch) of thisCalendarundefined. This means thatisSet()will returnfalsefor all the calendar fields, and the date and time calculations will treat the fields as if they had never been set. ACalendarimplementation class may use its specific default field values for date/time calculations. For example,GregorianCalendaruses 1970 if theYEARfield value is undefined.- See Also:
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clear
public final void clear(int field) Sets the given calendar field value and the time value (millisecond offset from the Epoch) of thisCalendarundefined. This means thatisSet(field)will returnfalse, and the date and time calculations will treat the field as if it had never been set. ACalendarimplementation class may use the field's specific default value for date and time calculations.The
HOUR_OF_DAY,HOURandAM_PMfields are handled independently and the the resolution rule for the time of day is applied. Clearing one of the fields doesn't reset the hour of day value of thisCalendar. Useset(Calendar.HOUR_OF_DAY, 0)to reset the hour value.- Parameters:
field- the calendar field to be cleared.- See Also:
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isSet
public final boolean isSet(int field) Determines if the given calendar field has a value set, including cases that the value has been set by internal fields calculations triggered by agetmethod call.- Parameters:
field- the calendar field to test- Returns:
trueif the given calendar field has a value set;falseotherwise.
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getDisplayName
Returns the string representation of the calendarfieldvalue in the givenstyleandlocale. If no string representation is applicable,nullis returned. This method callsget(field)to get the calendarfieldvalue if the string representation is applicable to the given calendarfield.For example, if this
Calendaris aGregorianCalendarand its date is 2005-01-01, then the string representation of theMONTHfield 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 theDAY_OF_MONTHfield, and this method would returnnull.The default implementation supports the calendar fields for which a
DateFormatSymbolshas names in the givenlocale.- Parameters:
field- the calendar field for which the string representation is returnedstyle- the style applied to the string representation; one ofSHORT_FORMAT(SHORT),SHORT_STANDALONE,LONG_FORMAT(LONG),LONG_STANDALONE,NARROW_FORMAT, orNARROW_STANDALONE.locale- the locale for the string representation (any calendar types specified bylocaleare ignored)- Returns:
- the string representation of the given
fieldin the givenstyle, ornullif no string representation is applicable. - Throws:
IllegalArgumentException- iffieldorstyleis invalid, or if thisCalendaris non-lenient and any of the calendar fields have invalid valuesNullPointerException- iflocaleis null- Since:
- 1.6
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getDisplayNames
Returns aMapcontaining all names of the calendarfieldin the givenstyleandlocaleand their corresponding field values. For example, if thisCalendaris aGregorianCalendar, the returned map would contain "Jan" toJANUARY, "Feb" toFEBRUARY, and so on, in the 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
Map.The values of other calendar fields may be taken into account to determine a set of display names. For example, if this
Calendaris a lunisolar calendar system and the year value given by theYEARfield 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
DateFormatSymbols. For example, iffieldisMONTHandstyleisALL_STYLES, this method returns aMapcontaining all strings returned byDateFormatSymbols.getShortMonths()andDateFormatSymbols.getMonths().- Parameters:
field- the calendar field for which the display names are returnedstyle- the style applied to the string representation; one ofSHORT_FORMAT(SHORT),SHORT_STANDALONE,LONG_FORMAT(LONG),LONG_STANDALONE,NARROW_FORMAT, orNARROW_STANDALONElocale- the locale for the display names- Returns:
- a
Mapcontaining all display names instyleandlocaleand their field values, ornullif no display names are defined forfield - Throws:
IllegalArgumentException- iffieldorstyleis invalid, or if thisCalendaris non-lenient and any of the calendar fields have invalid valuesNullPointerException- iflocaleis null- Since:
- 1.6
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complete
protected void complete()Fills in any unset fields in the calendar fields. First, thecomputeTime()method is called if the time value (millisecond offset from the Epoch) has not been calculated from calendar field values. Then, thecomputeFields()method is called to calculate all calendar field values. -
getAvailableCalendarTypes
Returns an unmodifiableSetcontaining all calendar types supported byCalendarin the runtime environment. The available calendar types can be used for the Unicode locale extensions. TheSetreturned contains at least"gregory". The calendar types don't include aliases, such as"gregorian"for"gregory".- Returns:
- an unmodifiable
Setcontaining all available calendar types - Since:
- 1.8
- See Also:
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getCalendarType
Returns the calendar type of thisCalendar. 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
Calendarinstance. Any subclasses that implement LDML-defined calendar systems should override this method to return appropriate calendar types.- Returns:
- the LDML-defined calendar type or the class name of this
Calendarinstance - Since:
- 1.8
- See Also:
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equals
Compares thisCalendarto the specifiedObject. The result istrueif and only if the argument is aCalendarobject of the same calendar system that represents the same time value (millisecond offset from the Epoch) under the sameCalendarparameters as this object.The
Calendarparameters are the values represented by theisLenient,getFirstDayOfWeek,getMinimalDaysInFirstWeekandgetTimeZonemethods. If there is any difference in those parameters between the twoCalendars, this method returnsfalse.Use the
compareTomethod to compare only the time values. -
hashCode
public int hashCode()Returns a hash code for this calendar. -
before
Returns whether thisCalendarrepresents a time before the time represented by the specifiedObject. This method is equivalent to:
if and only ifcompareTo(when) < 0whenis aCalendarinstance. Otherwise, the method returnsfalse.- Parameters:
when- theObjectto be compared- Returns:
trueif the time of thisCalendaris before the time represented bywhen;falseotherwise.- See Also:
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after
Returns whether thisCalendarrepresents a time after the time represented by the specifiedObject. This method is equivalent to:
if and only ifcompareTo(when) > 0whenis aCalendarinstance. Otherwise, the method returnsfalse.- Parameters:
when- theObjectto be compared- Returns:
trueif the time of thisCalendaris after the time represented bywhen;falseotherwise.- See Also:
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compareTo
Compares the time values (millisecond offsets from the Epoch) represented by twoCalendarobjects.- Specified by:
compareToin interfaceComparable<Calendar>- Parameters:
anotherCalendar- theCalendarto be compared.- Returns:
- the value
0if the time represented by the argument is equal to the time represented by thisCalendar; a value less than0if the time of thisCalendaris before the time represented by the argument; and a value greater than0if the time of thisCalendaris after the time represented by the argument. - Throws:
NullPointerException- if the specifiedCalendarisnull.IllegalArgumentException- if the time value of the specifiedCalendarobject can't be obtained due to any invalid calendar values.- Since:
- 1.5
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add
public abstract void add(int field, int amount) 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:add(Calendar.DAY_OF_MONTH, -5).- Parameters:
field- the calendar field.amount- the amount of date or time to be added to the field.- See Also:
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roll
public abstract void roll(int field, boolean up) Adds or subtracts (up/down) a single unit of time on the given time field without changing larger fields. For example, to roll the current date up by one day, you can achieve it by calling:roll(Calendar.DATE, true). When rolling on the year or Calendar.YEAR field, it will roll the year value in the range between 1 and the value returned by calling
getMaximum(Calendar.YEAR). When rolling on the month or Calendar.MONTH field, other fields like date might conflict and, need to be changed. For instance, rolling the month on the date 01/31/96 will result in 02/29/96. When rolling on the hour-in-day or Calendar.HOUR_OF_DAY field, it will roll the hour value in the range between 0 and 23, which is zero-based.- Parameters:
field- the time field.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 Also:
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roll
public void roll(int field, int amount) 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
Calendarjust repeatedly calls the version ofroll()that rolls by one unit. This may not always do the right thing. For example, if theDAY_OF_MONTHfield is 31, rolling through February will leave it set to 28. TheGregorianCalendarversion of this function takes care of this problem. Other subclasses should also provide overrides of this function that do the right thing.- Parameters:
field- the calendar field.amount- the signed amount to add to the calendarfield.- Since:
- 1.2
- See Also:
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setTimeZone
Sets the time zone with the given time zone value.- Parameters:
value- the given time zone.
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getTimeZone
Gets the time zone.- Returns:
- the time zone object associated with this calendar.
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setLenient
public void setLenient(boolean lenient) 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.- Parameters:
lenient-trueif the lenient mode is to be turned on;falseif it is to be turned off.- See Also:
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isLenient
public boolean isLenient()Tells whether date/time interpretation is to be lenient.- Returns:
trueif the interpretation mode of this calendar is lenient;falseotherwise.- See Also:
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setFirstDayOfWeek
public void setFirstDayOfWeek(int value) Sets what the first day of the week is; e.g.,SUNDAYin the U.S.,MONDAYin France.- Parameters:
value- the given first day of the week.- See Also:
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getFirstDayOfWeek
public int getFirstDayOfWeek()Gets what the first day of the week is; e.g.,SUNDAYin the U.S.,MONDAYin France.- Returns:
- the first day of the week.
- See Also:
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setMinimalDaysInFirstWeek
public void setMinimalDaysInFirstWeek(int value) 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.- Parameters:
value- the given minimal days required in the first week of the year.- See Also:
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getMinimalDaysInFirstWeek
public int getMinimalDaysInFirstWeek()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.- Returns:
- the minimal days required in the first week of the year.
- See Also:
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isWeekDateSupported
public boolean isWeekDateSupported()Returns whether thisCalendarsupports week dates.The default implementation of this method returns
false.- Returns:
trueif thisCalendarsupports week dates;falseotherwise.- Since:
- 1.7
- See Also:
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getWeekYear
public int getWeekYear()Returns the week year represented by thisCalendar. The week year is in sync with the week cycle. The first day of the first week is the first day of the week year.The default implementation of this method throws an
UnsupportedOperationException.- Returns:
- the week year of this
Calendar - Throws:
UnsupportedOperationException- if any week year numbering isn't supported in thisCalendar.- Since:
- 1.7
- See Also:
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setWeekDate
public void setWeekDate(int weekYear, int weekOfYear, int dayOfWeek) Sets the date of thisCalendarwith the given date specifiers - week year, week of year, and day of week.Unlike the
setmethod, all of the calendar fields andtimevalues are calculated upon return.If
weekOfYearis out of the valid week-of-year range inweekYear, theweekYearandweekOfYearvalues are adjusted in lenient mode, or anIllegalArgumentExceptionis thrown in non-lenient mode.The default implementation of this method throws an
UnsupportedOperationException.- Parameters:
weekYear- the week yearweekOfYear- the week number based onweekYeardayOfWeek- the day of week value: one of the constants for theDAY_OF_WEEKfield:SUNDAY, ...,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 modeUnsupportedOperationException- if any week year numbering isn't supported in thisCalendar.- Since:
- 1.7
- See Also:
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getWeeksInWeekYear
public int getWeeksInWeekYear()Returns the number of weeks in the week year represented by thisCalendar.The default implementation of this method throws an
UnsupportedOperationException.- Returns:
- the number of weeks in the week year.
- Throws:
UnsupportedOperationException- if any week year numbering isn't supported in thisCalendar.- Since:
- 1.7
- See Also:
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getMinimum
public abstract int getMinimum(int field) Returns the minimum value for the given calendar field of thisCalendarinstance. The minimum value is defined as the smallest value returned by thegetmethod for any possible time value. The minimum value depends on calendar system specific parameters of the instance.- Parameters:
field- the calendar field.- Returns:
- the minimum value for the given calendar field.
- See Also:
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getMaximum
public abstract int getMaximum(int field) Returns the maximum value for the given calendar field of thisCalendarinstance. The maximum value is defined as the largest value returned by thegetmethod for any possible time value. The maximum value depends on calendar system specific parameters of the instance.- Parameters:
field- the calendar field.- Returns:
- the maximum value for the given calendar field.
- See Also:
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getGreatestMinimum
public abstract int getGreatestMinimum(int field) Returns the highest minimum value for the given calendar field of thisCalendarinstance. The highest minimum value is defined as the largest value returned bygetActualMinimum(int)for any possible time value. The greatest minimum value depends on calendar system specific parameters of the instance.- Parameters:
field- the calendar field.- Returns:
- the highest minimum value for the given calendar field.
- See Also:
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getLeastMaximum
public abstract int getLeastMaximum(int field) Returns the lowest maximum value for the given calendar field of thisCalendarinstance. The lowest maximum value is defined as the smallest value returned bygetActualMaximum(int)for any possible time value. The least maximum value depends on calendar system specific parameters of the instance. For example, aCalendarfor the Gregorian calendar system returns 28 for theDAY_OF_MONTHfield, because the 28th is the last day of the shortest month of this calendar, February in a common year.- Parameters:
field- the calendar field.- Returns:
- the lowest maximum value for the given calendar field.
- See Also:
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getActualMinimum
public int getActualMinimum(int field) Returns the minimum value that the specified calendar field could have, given the time value of thisCalendar.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
getMinimum().- Parameters:
field- the calendar field- Returns:
- the minimum of the given calendar field for the time
value of this
Calendar - Since:
- 1.2
- See Also:
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getActualMaximum
public int getActualMaximum(int field) Returns the maximum value that the specified calendar field could have, given the time value of thisCalendar. For example, the actual maximum value of theMONTHfield 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.
- Parameters:
field- the calendar field- Returns:
- the maximum of the given calendar field for the time
value of this
Calendar - Since:
- 1.2
- See Also:
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clone
Creates and returns a copy of this object. -
toString
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 benull. -
toInstant
Converts this object to anInstant.The conversion creates an
Instantthat represents the same point on the time-line as thisCalendar.- Returns:
- the instant representing the same point on the time-line
- Since:
- 1.8
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