java.util
Class Calendar

java.lang.Object
  java.util.Calendar

All Implemented Interfaces:

Cloneable , Comparable , Serializable

Direct Known Subclasses:

GregorianCalendar

public abstract class Calendar

extends Object

implements Serializable , Cloneable , Comparable < Calendar >

The Calendar class is an abstract class that provides methods for converting between a specific instant in time and a set of calendar fields Calendar is an abstract base class for converting between a Date object and a set of integer fields such as YEAR, MONTH, DAY, HOUR, and so on. (A Date object represents a specific instant in time with millisecond precision. See Date 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). for information about the Date class.)

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

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

     Calendar rightNow = Calendar.getInstance();
 

A Calendar object can produce all the calendar time field values needed to implement the date-time formatting for a particular language and calendar style (for example, Japanese-Gregorian, Japanese-Traditional). Calendar defines the range of values returned by certain calendar fields, as well as their meaning. For example, the first month of the calendar system year has value MONTH == JANUARY for all calendars. Other values are defined by the concrete subclass, such as ERA. ERA and YEAR. 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. When a Calendar is lenient, it accepts a wider range of field values than it produces. For example, a lenient GregorianCalendar interprets MONTH == JANUARY, DAY_OF_MONTH == 32 as February 1. A non-lenient GregorianCalendar throws an exception when given out-of-range field settings. When calendars recompute field values for return by get(), they normalize them. For example, a GregorianCalendar always produces DAY_OF_MONTH values between 1 and the length of the month.

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

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

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. When computing a Date from time fields, two special circumstances may arise: there may be insufficient information to compute the Date (such as only year and month but no day in the month), or there may be inconsistent information (such as "Tuesday, July 15, 1996" -- July 15, 1996 is actually a Monday).

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

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

For the date 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: for some non-Gregorian calendars, different fields may be necessary for complete disambiguation. For example, a full specification of the historical Arabic astronomical calendar requires year, month, day-of-month and day-of-week in some cases.

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

1. 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.
2. 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

Field manipulation methods

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() getTimeInMillis() 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 calendar to September 31, 1999. This is a temporary internal representation that resolves to October 1, 1999 if getTime()is then called. However, a call to set(Calendar.DAY_OF_MONTH, 30) before the call to getTime() sets the date calendar to September 30, 1999, since no recomputation occurs after set() itself.

add(f, delta) adds delta to field f. This is equivalent to calling set(f, get(f) + delta) with two adjustments:

Add rule 1. The value of field f after the call minus the value of field f before the call is delta, modulo any overflow that has occurred in field f. Overflow occurs when a field value exceeds its range and, as a result, the next larger field is incremented or decremented and the field value is adjusted back into its range.

Add rule 2. If a smaller field is expected to be invariant, but   it is impossible for it to be equal to its prior value because of changes in its minimum or maximum after field f is changed or other constraints, such as time zone offset changes, changed, then its value is adjusted to be as close as possible to its expected value. A smaller field represents a smaller unit of time. HOUR is a smaller field than DAY_OF_MONTH. No adjustment is made to smaller fields that are not expected to be invariant. The calendar system determines what fields are expected to be invariant.

In addition, unlike set(), add() forces an immediate recomputation of the calendar's milliseconds and all fields.

Example: Consider a GregorianCalendar originally set to August 31, 1999. Calling add(Calendar.MONTH, 13) sets the calendar to September 30, 2000. Add rule 1 sets the MONTH field to September, since adding 13 months to August gives September of the next year. Since DAY_OF_MONTH cannot be 31 in September in a GregorianCalendar, add rule 2 sets the DAY_OF_MONTH to 30, the closest possible value. Although it is a smaller field, DAY_OF_WEEK is not adjusted by rule 2, since it is expected to change when the month changes in a GregorianCalendar.

roll(f, delta) adds delta to field f without changing larger fields. This is equivalent to calling add(f, delta) with the following adjustment:

Roll rule. Larger fields are unchanged after the call. A larger field represents a larger unit of time. DAY_OF_MONTH is a larger field than HOUR.

Example: See 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:

JDK1.1

See Also:

System.currentTimeMillis() Date , Date , GregorianCalendar , TimeZone , DateFormat , Serialized Form

Field Summary
static int	AM           Value of the AM_PM AM_PM field indicating the period of the day from midnight to just before noon.
static int	AM_PM           Field number for get and set indicating whether the HOUR is before or after noon.
static int	APRIL           Value of the MONTH MONTH field indicating the fourth month of the year.
protected  boolean	areFieldsSet           True if fields[] are in sync with the currently set time.
static int	AUGUST           Value of the MONTH MONTH field indicating the eighth month of the year.
static int	DATE           Field number for get and set indicating the day of the month.
static int	DAY_OF_MONTH           Field number for get and set indicating the day of the month.
static int	DAY_OF_WEEK           Field number for get and set indicating the day of the week.
static int	DAY_OF_WEEK_IN_MONTH           Field number for get and set indicating the ordinal number of the day of the week within the current month.
static int	DAY_OF_YEAR           Field number for get and set indicating the day number within the current year.
static int	DECEMBER           Value of the MONTH MONTH field indicating the twelfth month of the year.
static int	DST_OFFSET           Field number for get and set indicating the daylight savings offset in milliseconds.
static int	ERA           Field number for get and set indicating the era, e.g., AD or BC in the Julian calendar.
static int	FEBRUARY           Value of the MONTH MONTH field indicating the second month of the year.
static int	FIELD_COUNT           The number of distinct fields recognized by get and set.
protected  int[]	fields           The calendar field values for the currently set time for this calendar.
static int	FRIDAY           Value of the DAY_OF_WEEK DAY_OF_WEEK field indicating Friday.
static int	HOUR           Field number for get and set indicating the hour of the morning or afternoon.
static int	HOUR_OF_DAY           Field number for get and set indicating the hour of the day.
protected  boolean[]	isSet           The flags which tell if a specified calendar time field for the calendar is set.
protected  boolean	isTimeSet           True if then the value of time is valid.
static int	JANUARY           Value of the MONTH MONTH field indicating the first month of the year.
static int	JULY           Value of the MONTH MONTH field indicating the seventh month of the year.
static int	JUNE           Value of the MONTH MONTH field indicating the sixth month of the year.
static int	MARCH           Value of the MONTH MONTH field indicating the third month of the year.
static int	MAY           Value of the MONTH MONTH field indicating the fifth month of the year.
static int	MILLISECOND           Field number for get and set indicating the millisecond within the second.
static int	MINUTE           Field number for get and set indicating the minute within the hour.
static int	MONDAY           Value of the DAY_OF_WEEK DAY_OF_WEEK field indicating Monday.
static int	MONTH           Field number for get and set indicating the month.
static int	NOVEMBER           Value of the MONTH MONTH field indicating the eleventh month of the year.
static int	OCTOBER           Value of the MONTH MONTH field indicating the tenth month of the year.
static int	PM           Value of the AM_PM AM_PM field indicating the period of the day from noon to just before midnight.
static int	SATURDAY           Value of the DAY_OF_WEEK DAY_OF_WEEK field indicating Saturday.
static int	SECOND           Field number for get and set indicating the second within the minute.
static int	SEPTEMBER           Value of the MONTH MONTH field indicating the ninth month of the year.
static int	SUNDAY           Value of the DAY_OF_WEEK DAY_OF_WEEK field indicating Sunday.
static int	THURSDAY           Value of the DAY_OF_WEEK DAY_OF_WEEK field indicating Thursday.
protected  long	time           The currently set time for this calendar, expressed in milliseconds after January 1, 1970, 0:00:00 GMT.
static int	TUESDAY           Value of the DAY_OF_WEEK DAY_OF_WEEK field indicating Tuesday.
static int	UNDECIMBER           Value of the MONTH MONTH field indicating the thirteenth month of the year.
static int	WEDNESDAY           Value of the DAY_OF_WEEK DAY_OF_WEEK field indicating Wednesday.
static int	WEEK_OF_MONTH           Field number for get and set indicating the week number within the current month.
static int	WEEK_OF_YEAR           Field number for get and set indicating the week number within the current year.
static int	YEAR           Field number for get and set indicating the year.
static int	ZONE_OFFSET           Field number for get and set indicating the raw offset from GMT in milliseconds.

 

Constructor Summary
protected	Calendar ()           Constructs a Calendar with the default time zone and locale.
protected	Calendar ( TimeZone  zone, Locale  aLocale)           Constructs a calendar with the specified time zone and locale.

 

Method Summary
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.           Date Arithmetic function.
boolean	after ( Object           Returns whether this Calendar represents a time after           Compares the time represented by the specified Object. field records.
boolean	before ( Object           Returns whether this Calendar represents a time before           Compares the time represented by the specified Object. field records.
void	clear ()           Sets all           Clears the calendar field values and of all the time value (millisecond offset from the Epoch fields.
void	clear (int field)           Sets           Clears the given calendar field value and in the given time value (millisecond offset from the Epoch field.
Object	clone ()           Creates and returns a copy of this object.           Overrides Cloneable
int	compareTo ( Calendar           Compares the time values (millisecond offsets from the Epoch
protected  void	complete ()           Fills in any unset fields in the time field list.
protected abstract  void	complete computeFields ()           Fills           Converts the current millisecond time value time to field values in any unset fields in the calendar fields. fields[].
protected abstract  void	computeFields computeTime ()           Converts the current field values in fields[] to the millisecond time value time to calendar field values in fields[] time.
protected abstract  void	computeTime ()           Converts the current calendar field values in fields[] to the millisecond time value time
boolean	equals ( Object           Compares this calendar to the specified object.
boolean	equals ( Object           Compares this Calendar to the specified Object.
int	get (int field)           Gets the value for a given time field.
int	get getActualMaximum (int field)           Returns           Return the maximum value of that this field could have, given the given calendar field. current date.
int	getActualMaximum getActualMinimum (int field)           Returns           Return the maximum minimum value that the specified calendar this field could have, given the current date.
int	getActualMinimum (int field)           Returns the minimum value that the specified calendar field could have, given the current date.
static  Locale	getAvailableLocales ()           Gets the list of locales for which Calendars are installed.
static  Locale	getAvailableLocales ()           Returns an array of all locales for which the getInstance methods of this class can return localized instances.
int	getFirstDayOfWeek ()           Gets what the first day of the week is; e.g., Sunday in US, Monday in France.
int	getFirstDayOfWeek ()           Gets what the first day of the week is; e.g., SUNDAY in the U.S., MONDAY in France.
abstract  int	getGreatestMinimum (int field)           Gets the highest minimum value for the given field if varies.
abstract  int	getGreatestMinimum (int field)           Gets the highest minimum value for the given calendar field if varies.
static  Calendar	getInstance ()           Gets a calendar using the default time zone and locale.
static  Calendar	getInstance ( Locale  aLocale)           Gets a calendar using the default time zone and specified locale.
static  Calendar	getInstance ( TimeZone  zone)           Gets a calendar using the specified time zone and default locale.
static  Calendar	getInstance ( TimeZone  zone, Locale  aLocale)           Gets a calendar with the specified time zone and locale.
abstract  int	getLeastMaximum (int field)           Gets the lowest maximum value for the given calendar field if varies.
abstract  int	getMaximum (int field)           Gets the maximum value for the given calendar time field.
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 getMinimalDaysInFirstWeek returns 1.
abstract  int	getMinimum (int field)           Gets the minimum value for the given calendar time field.
Date	getTime ()           Returns a Date object represending           Gets this Calendar's time value (millisecond offset from the Epoch current time.
long	getTimeInMillis ()           Returns           Gets this Calendar's current time value in milliseconds. as a long.
TimeZone	getTimeZone ()           Gets the time zone.
int	hashCode ()           Returns a hash code for this calendar.
protected  int	internalGet (int field)           Returns           Gets the value of the for a given calendar time field.
boolean	isLenient ()           Tells           Tell whether date/time interpretation is to be lenient.
boolean	isSet (int field)           Determines if the given calendar time field has a value set, including cases that the value has been set by internal fields calculations triggered by a get method call. set.
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.           Time Field Rolling function.
void	roll (int field, int amount)           Adds the specified (signed) amount to the specified calendar field without changing larger fields.           Time Field Rolling function.
void	set (int field, int value)           Sets the given calendar time field to with the given value.
void	set (int year, int month, int date)           Sets the values for the calendar fields YEAR, MONTH, year, month, and DAY_OF_MONTH. date.
void	set (int year, int month, int date, int hourOfDay, int hour, int minute)           Sets the values for the calendar fields YEAR, MONTH, DAY_OF_MONTH, HOUR_OF_DAY, year, month, date, hour, and MINUTE. minute.
void	set (int year, int month, int date, int hourOfDay, int hour, int minute, int second)           Sets the values for the fields YEAR, MONTH, DAY_OF_MONTH, HOUR, MINUTE, year, month, date, hour, minute, and SECOND. second.
void	setFirstDayOfWeek (int value)           Sets what the first day of the week is; e.g., SUNDAY Sunday in the U.S., MONDAY US, Monday in France.
void	setLenient (boolean lenient)           Specifies           Specify whether or not date/time interpretation is to be lenient.
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 the method with value 1.
void	setTime ( Date           Sets this Calendar's current time with the given Date.
void	setTimeInMillis (long millis)           Sets this Calendar's current time from the given long value.
void	setTimeZone ( TimeZone  value)           Sets the time zone with the given time zone value.
String	toString ()           Return a string representation of this calendar.

 

Methods inherited from class java.lang. Object
finalize , getClass , notify , notifyAll , wait , wait , wait

 

Methods inherited from interface java.lang. Comparable
compareTo

 

Field Detail

ERA

public static final int ERA

Field number for get and set indicating the era, e.g., AD or BC in the Julian calendar. This is a calendar-specific value; see subclass documentation.

See Also:

GregorianCalendar.AD , GregorianCalendar.BC , Constant Field Values

YEAR

public static final int YEAR

Field number for get and set indicating the year. This is a calendar-specific value; see subclass documentation.

See Also:

Constant Field Values

MONTH

public static final int MONTH

Field number for get and set indicating the month. This is a calendar-specific value. The first month of the year is JANUARY which is 0; the last depends on the number of months in a year.

See Also:

JANUARY , FEBRUARY , MARCH , APRIL , MAY , JUNE , JULY , AUGUST , SEPTEMBER , OCTOBER , NOVEMBER , DECEMBER , UNDECIMBER , Constant Field Values

WEEK_OF_YEAR

public static final int WEEK_OF_YEAR

Field number for get and set indicating the week number within the current year. The first week of the year, as defined by getFirstDayOfWeek() and getMinimalDaysInFirstWeek(), has value 1. Subclasses define the value of WEEK_OF_YEAR for days before the first week of the year.

See Also:

getFirstDayOfWeek() , getMinimalDaysInFirstWeek() , Constant Field Values

WEEK_OF_MONTH

public static final int WEEK_OF_MONTH

Field number for get and set indicating the week number within the current month. The first week of the month, as defined by getFirstDayOfWeek() and getMinimalDaysInFirstWeek(), has value 1. Subclasses define the value of WEEK_OF_MONTH for days before the first week of the month.

See Also:

getFirstDayOfWeek() , getMinimalDaysInFirstWeek() , Constant Field Values

DATE

public static final int DATE

Field number for get and set indicating the day of the month. This is a synonym for DAY_OF_MONTH. The first day of the month has value 1.

See Also:

DAY_OF_MONTH , Constant Field Values

DAY_OF_MONTH

public static final int DAY_OF_MONTH

Field number for get and set indicating the day of the month. This is a synonym for DATE. The first day of the month has value 1.

See Also:

DATE , Constant Field Values

DAY_OF_YEAR

public static final int DAY_OF_YEAR

Field number for get and set indicating the day number within the current year. The first day of the year has value 1.

See Also:

Constant Field Values

DAY_OF_WEEK

public static final int DAY_OF_WEEK

Field number for get and set indicating the day of the week. This field takes values SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, and SATURDAY.

See Also:

SUNDAY , MONDAY , TUESDAY , WEDNESDAY , THURSDAY , FRIDAY , SATURDAY , Constant Field Values

DAY_OF_WEEK_IN_MONTH

public static final int DAY_OF_WEEK_IN_MONTH

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

See Also:

DAY_OF_WEEK , WEEK_OF_MONTH , Constant Field Values

AM_PM

public static final int AM_PM

Field number for get and set indicating whether the HOUR is before or after noon. E.g., at 10:04:15.250 PM the AM_PM is PM.

See Also:

AM , PM , HOUR , Constant Field Values

HOUR

public static final int HOUR

Field number for get and set indicating the hour of the morning or afternoon. HOUR is used for the 12-hour clock (0 - 11). Noon and midnight are represented by 0, not by 12. HOUR is used for the 12-hour clock. E.g., at 10:04:15.250 PM the HOUR is 10.

See Also:

AM_PM , HOUR_OF_DAY , Constant Field Values

HOUR_OF_DAY

public static final int HOUR_OF_DAY

Field number for get and set indicating the hour of the day. HOUR_OF_DAY is used for the 24-hour clock. E.g., at 10:04:15.250 PM the HOUR_OF_DAY is 22.

See Also:

HOUR , Constant Field Values

MINUTE

public static final int MINUTE

Field number for get and set indicating the minute within the hour. E.g., at 10:04:15.250 PM the MINUTE is 4.

See Also:

Constant Field Values

SECOND

public static final int SECOND

Field number for get and set indicating the second within the minute. E.g., at 10:04:15.250 PM the SECOND is 15.

See Also:

Constant Field Values

MILLISECOND

public static final int MILLISECOND

Field number for get and set indicating the millisecond within the second. E.g., at 10:04:15.250 PM the MILLISECOND is 250.

See Also:

Constant Field Values

ZONE_OFFSET

public static final int ZONE_OFFSET

Field number for get and set indicating the raw offset from GMT in milliseconds.

This field reflects the correct GMT offset value of the time zone of this Calendar if the TimeZone implementation subclass supports historical GMT offset changes.

See Also:

Constant Field Values

DST_OFFSET

public static final int DST_OFFSET

Field number for get and set indicating the daylight savings offset in milliseconds.

This field reflects the correct daylight saving offset value of the time zone of this Calendar if the TimeZone implementation subclass supports historical Daylight Saving Time schedule changes.

See Also:

Constant Field Values

FIELD_COUNT

public static final int FIELD_COUNT

The number of distinct fields recognized by get and set. Field numbers range from 0..FIELD_COUNT-1.

See Also:

Constant Field Values

SUNDAY

public static final int SUNDAY

Value of the DAY_OF_WEEK DAY_OF_WEEK field indicating Sunday.

See Also:

Constant Field Values

MONDAY

public static final int MONDAY

Value of the DAY_OF_WEEK DAY_OF_WEEK field indicating Monday.

See Also:

Constant Field Values

TUESDAY

public static final int TUESDAY

Value of the DAY_OF_WEEK DAY_OF_WEEK field indicating Tuesday.

See Also:

Constant Field Values

WEDNESDAY

public static final int WEDNESDAY

Value of the DAY_OF_WEEK DAY_OF_WEEK field indicating Wednesday.

See Also:

Constant Field Values

THURSDAY

public static final int THURSDAY

Value of the DAY_OF_WEEK DAY_OF_WEEK field indicating Thursday.

See Also:

Constant Field Values

FRIDAY

public static final int FRIDAY

Value of the DAY_OF_WEEK DAY_OF_WEEK field indicating Friday.

See Also:

Constant Field Values

SATURDAY

public static final int SATURDAY

Value of the DAY_OF_WEEK DAY_OF_WEEK field indicating Saturday.

See Also:

Constant Field Values

JANUARY

public static final int JANUARY

Value of the MONTH MONTH field indicating the first month of the year.

See Also:

Constant Field Values

FEBRUARY

public static final int FEBRUARY

Value of the MONTH MONTH field indicating the second month of the year.

See Also:

Constant Field Values

MARCH

public static final int MARCH

Value of the MONTH MONTH field indicating the third month of the year.

See Also:

Constant Field Values

APRIL

public static final int APRIL

Value of the MONTH MONTH field indicating the fourth month of the year.

See Also:

Constant Field Values

MAY

public static final int MAY

Value of the MONTH MONTH field indicating the fifth month of the year.

See Also:

Constant Field Values

JUNE

public static final int JUNE

Value of the MONTH MONTH field indicating the sixth month of the year.

See Also:

Constant Field Values

JULY

public static final int JULY

Value of the MONTH MONTH field indicating the seventh month of the year.

See Also:

Constant Field Values

AUGUST

public static final int AUGUST

Value of the MONTH MONTH field indicating the eighth month of the year.

See Also:

Constant Field Values

SEPTEMBER

public static final int SEPTEMBER

Value of the MONTH MONTH field indicating the ninth month of the year.

See Also:

Constant Field Values

OCTOBER

public static final int OCTOBER

Value of the MONTH MONTH field indicating the tenth month of the year.

See Also:

Constant Field Values

NOVEMBER

public static final int NOVEMBER

Value of the MONTH MONTH field indicating the eleventh month of the year.

See Also:

Constant Field Values

DECEMBER

public static final int DECEMBER

Value of the MONTH MONTH field indicating the twelfth month of the year.

See Also:

Constant Field Values

UNDECIMBER

public static final int UNDECIMBER

Value of the MONTH MONTH field indicating the thirteenth month of the year. Although GregorianCalendar does not use this value, lunar calendars do.

See Also:

Constant Field Values

AM

public static final int AM

Value of the AM_PM AM_PM field indicating the period of the day from midnight to just before noon.

See Also:

Constant Field Values

PM

public static final int PM

Value of the AM_PM AM_PM field indicating the period of the day from noon to just before midnight.

See Also:

Constant Field Values

fields

protected int[] fields

The calendar field values for the currently set time for this calendar. This is an array of FIELD_COUNT integers, with index values ERA through DST_OFFSET.

isSet

protected boolean[] isSet

The flags which tell if a specified calendar time field for the calendar is set. A new object has no fields set. After the first call to a method which generates the fields, they all remain set after that. This is an array of FIELD_COUNT booleans, with index values ERA through DST_OFFSET.

time

protected long time

The currently set time for this calendar, expressed in milliseconds after January 1, 1970, 0:00:00 GMT.

See Also:

isTimeSet

isTimeSet

protected boolean isTimeSet

True if then the value of time is valid. The time is made invalid by a change to an item of field[].

See Also:

time

areFieldsSet

protected boolean areFieldsSet

True if fields[] are in sync with the currently set time. If false, then the next attempt to get the value of a field will force a recomputation of all fields from the current value of time.

Calendar

protected Calendar()

Constructs a Calendar with the default time zone and locale.

See Also:

TimeZone.getDefault()

Calendar

protected Calendar(TimeZone zone,
                   Locale aLocale)

Constructs a calendar with the specified time zone and locale.

Parameters:

zone - the time zone to use

aLocale - the locale for the week data

getInstance

public static Calendar getInstance()

Gets a calendar using the default time zone and locale. The Calendar returned is based on the current time in the default time zone with the default locale.

Returns:

a Calendar.

getInstance

public static Calendar getInstance(TimeZone zone)

Gets a calendar using the specified time zone and default locale. The Calendar returned is based on the current time in the given time zone with the default locale.

Parameters:

zone - the time zone to use

Returns:

a Calendar.

getInstance

public static Calendar getInstance(Locale aLocale)

Gets a calendar using the default time zone and specified locale. The Calendar returned is based on the current time in the default time zone with the given locale.

Parameters:

aLocale - the locale for the week data

Returns:

a Calendar.

getInstance

public static Calendar getInstance(TimeZone zone,
                                   Locale aLocale)

Gets a calendar with the specified time zone and locale. The Calendar returned is based on the current time in the given time zone with the given locale.

Parameters:

zone - the time zone to use

aLocale - the locale for the week data

Returns:

a Calendar.

getAvailableLocales

public static Locale[] getAvailableLocales()

Returns an array of all locales for which the getInstance methods of this class can return localized instances. The array returned must contain at least a Locale instance equal to Locale.US . Gets the list of locales for which Calendars are installed.

Returns:

An array the list of locales for which localized Calendar instances Calendars are available. installed.

computeTime

protected abstract void computeTime()

Converts the current calendar field values in fields[] fields[] to the millisecond time value time . time.

See Also:

complete() , computeFields()

computeFields

protected abstract void computeFields()

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

See Also:

computeTime() complete()

getTime

public final Date getTime()

Returns a Date object represending this Calendar's time value (millisecond offset from the Epoch "). Gets this Calendar's current time.

Returns:

a Date representing the time value. the current time.

See Also:

setTime(Date) setTime(java.util.Date) , getTimeInMillis()

setTime

public final void setTime(Date date)

Sets this Calendar's current time with the given Date.

Note: Calling setTime() with Date(Long.MAX_VALUE) or Date(Long.MIN_VALUE) may yield incorrect field values from get().

Parameters:

date - the given Date.

See Also:

getTime() , setTimeInMillis(long)

getTimeInMillis

public long getTimeInMillis()

Returns this Calendar's time value in milliseconds. Gets this Calendar's current time as a long.

Returns:

the current time as UTC milliseconds from the epoch.

See Also:

getTime() , setTimeInMillis(long)

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:

setTime(Date) setTime(java.util.Date) , getTimeInMillis()

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 the complete() method, which process is calendar system dependent. Gets the value for a given time field.

Parameters:

field - the given calendar time field.

Returns:

the value for the given calendar time field.

Throws:

ArrayIndexOutOfBoundsException - if the specified field is out of range (field ( field < 0 || field >= FIELD_COUNT).

See Also:

set(int,int) , complete() FIELD_COUNT ).

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. Gets the value for a given time field. This is an internal fast time field value getter for the subclasses.

Parameters:

field - the given calendar time field.

Returns:

the value for the given calendar time field.

See Also:

get(int)

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. Sets the time field with the given value.

Parameters:

field - the given calendar time field.

value - the value to be set for the given calendar time field.

Throws:

ArrayIndexOutOfBoundsException - if the specified field is out of range (field < 0 || field >= FIELD_COUNT). in non-lenient mode.

See Also:

set(int,int,int) , set(int,int,int,int,int) , set(int,int,int,int,int,int) , get(int) - if specified field is out of range ( field < 0 || field >= FIELD_COUNT ).

set

public final void set(int year,
                      int month,
                      int date)

Sets the values for the calendar fields YEAR, MONTH, year, month, and DAY_OF_MONTH. date. Previous values of other calendar fields are retained. If this is not desired, call clear() clear first.

Parameters:

year - the value used to set the YEAR calendar time field.

month - the value used to set the MONTH calendar time field. Month value is 0-based. e.g., 0 for January.

date - the value used to set the DAY_OF_MONTH calendar DATE time field.

See Also:

set(int,int) , set(int,int,int,int,int) , set(int,int,int,int,int,int)

set

public final void set(int year,
 int month,
 int date,
 int hourOfDay,
 int hour,
 int minute) 

Sets the values for the calendar fields YEAR, MONTH, DAY_OF_MONTH, HOUR_OF_DAY, year, month, date, hour, and MINUTE. minute. Previous values of other fields are retained. If this is not desired, call clear() clear first.

Parameters:

year - the value used to set the YEAR calendar time field.

month - the value used to set the MONTH calendar time field. Month value is 0-based. e.g., 0 for January.

date - the value used to set the DAY_OF_MONTH calendar DATE time field.

hourOfDay hour - the value used to set the HOUR_OF_DAY calendar time field.

minute - the value used to set the MINUTE calendar time field.

See Also:

set(int,int) , set(int,int,int) , set(int,int,int,int,int,int)

set

public final void set(int year,
 int month,
 int date,
 int hourOfDay,
 int hour,
 int minute,
 int second) 

Sets the values for the fields YEAR, MONTH, DAY_OF_MONTH, HOUR, MINUTE, year, month, date, hour, minute, and SECOND. second. Previous values of other fields are retained. If this is not desired, call clear() clear first.

Parameters:

year - the value used to set the YEAR calendar time field.

month - the value used to set the MONTH calendar time field. Month value is 0-based. e.g., 0 for January.

date - the value used to set the DAY_OF_MONTH calendar DATE time field.

hourOfDay hour - the value used to set the HOUR_OF_DAY calendar time field.

minute - the value used to set the MINUTE calendar time field.

second - the value used to set the SECOND calendar time field.

See Also:

set(int,int) , set(int,int,int) , set(int,int,int,int,int)

clear

public final void clear()

Sets all the calendar field values and the time value (millisecond offset from the Epoch ) of this Calendar undefined. This means that isSet() will return false for all the calendar fields, and the date and time calculations will treat the fields as if they had never been set. A Calendar implementation class may use its specific default field values for date/time calculations. For example, GregorianCalendar uses 1970 if the YEAR field value is undefined. Clears the values of all the time fields.

See Also:

clear(int)

clear

public final void clear(int field)

Sets the given calendar field value and the time value (millisecond offset from the Epoch ) of this Calendar undefined. This means that isSet(field) will return false, and the date and time calculations will treat the field as if it had never been set. A Calendar implementation class may use the field's specific default value for date and time calculations. Clears the value in the given time field.

The HOUR_OF_DAY , HOUR and AM_PM fields 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 this Calendar. Use set(Calendar.HOUR_OF_DAY, 0) to reset the hour value.

Parameters:

field - the calendar time field to be cleared.

See Also:

clear()

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 a get method call. Determines if the given time field has a value set.

Returns:

true if the given calendar time field has a value set; false otherwise.

complete

protected void complete()

Fills in any unset fields in the calendar fields. First, the computeTime() method is called if the time value (millisecond offset from the Epoch ) has not been calculated from calendar field values. Then, the computeFields() method is called to calculate all calendar field values. Fills in any unset fields in the time field list.

equals

public boolean equals(Object obj)

Compares this Calendar calendar to the specified Object. object. The result is true if and only if the argument is not null and is a Calendar object of the same calendar system that represents the same time value (millisecond offset from the Epoch ) under the same Calendar parameters calendar as this object.

The Calendar parameters are the values represented by the isLenient, getFirstDayOfWeek, getMinimalDaysInFirstWeek and getTimeZone methods. If there is any difference in those parameters between the two Calendars, this method returns false.

Use the compareTo method to compare only the time values.

Overrides:

equals in class Object

Parameters:

obj - the object to compare with.

Returns:

true if this object is equal to obj; false otherwise. true if the objects are the same; false otherwise.

See Also:

Object.hashCode() , Hashtable

hashCode

public int hashCode()

Returns a hash code for this calendar.

Overrides:

hashCode in class Object

Returns:

a hash code value for this object.

Since:

1.2

See Also:

Object.equals(java.lang.Object) , Hashtable

before

public boolean before(Object when)

Returns whether this Calendar represents a time before the time represented by the specified Object. This method is equivalent to:

 compareTo(when) < 0
 

if and only if when is a Calendar instance. Otherwise, the method returns false. Compares the time field records. Equivalent to comparing result of conversion to UTC.

Parameters:

when - the Object Calendar to be compared with this Calendar.

Returns:

true if the current time of this Calendar is before the time represented by of Calendar when; false otherwise.

See Also:

compareTo(Calendar)

after

public boolean after(Object when)

Returns whether this Calendar represents a time after the time represented by the specified Object. This method is equivalent to:

 compareTo(when) > 0
 

if and only if when is a Calendar instance. Otherwise, the method returns false. Compares the time field records. Equivalent to comparing result of conversion to UTC.

Parameters:

when - the Object Calendar to be compared with this Calendar.

Returns:

true if the current time of this Calendar is after the time represented by of Calendar when; false otherwise.

See Also:

compareTo(Calendar)

compareTo

 
public int compareTo ( Calendar anotherCalendar) 

Compares the time values (millisecond offsets from the Epoch ) represented by two Calendar objects.

Parameters:

anotherCalendar - the Calendar to be compared.

Returns:

the value 0 if the time represented by the argument is equal to the time represented by this Calendar; a value less than 0 if the time of this Calendar is before the time represented by the argument; and a value greater than 0 if the time of this Calendar is after the time represented by the argument.

Throws:

NullPointerException - if the specified Calendar is null.

IllegalArgumentException - if the time value of the specified Calendar object can't be obtained due to any invalid calendar values.

Since:

1.5

add

public abstract void add(int field,
                         int amount)

Date Arithmetic function. Adds or subtracts the specified (signed) amount of time to the given calendar time field, based on the calendar's rules. For example, to subtract 5 days from the current time of the calendar, you can achieve it by calling:

add(Calendar.DAY_OF_MONTH, add(Calendar.DATE, -5).

Parameters:

field - the calendar time field.

amount - the amount of date or time to be added to the field.

See Also:

roll(int,int) , set(int,int)

roll

public abstract void roll(int field,
                          boolean up)

Time Field Rolling function. Adds or subtracts (up/down) a single unit of time on the given time field without changing larger fields. For example, to roll the current date up by one day, you can achieve it by calling:

roll(Calendar.DATE, true). When rolling on the year or Calendar.YEAR field, it will roll the year value in the range between 1 and the value returned by calling getMaximum(Calendar.YEAR). When rolling on the month or Calendar.MONTH field, other fields like date might conflict and, need to be changed. For instance, rolling the month on the date 01/31/96 will result in 02/29/96. When rolling on the hour-in-day or Calendar.HOUR_OF_DAY field, it will roll the hour value in the range between 0 and 23, which is zero-based.

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:

add(int,int) add(int, int) , set(int,int) set(int, int)

roll

public void roll(int field,
                 int amount)

Adds the specified (signed) amount Time Field Rolling function. Add to the specified calendar field a signed amount without changing larger fields. A negative roll amount means to roll down.

NOTE: [NOTE: This default implementation on Calendar just repeatedly calls the version of roll() roll() that takes a boolean and rolls by one unit. This may not always do the right thing. For example, if the DAY_OF_MONTH field is 31, rolling through February will leave it set to 28. The GregorianCalendar version of this function takes care of this problem. Other subclasses should also provide overrides of this function that do the right thing.

Parameters:

field - the calendar time field.

amount - the signed amount to add to the calendar field.

Since:

1.2

See Also:

roll(int,boolean) add(int, int) , add(int,int) set(int, int) , set(int,int)

setTimeZone

public void setTimeZone(TimeZone value)

Sets the time zone with the given time zone value.

Parameters:

value - the given time zone.

getTimeZone

public TimeZone getTimeZone()

Gets the time zone.

Returns:

the time zone object associated with this calendar.

setLenient

public void setLenient(boolean lenient)

Specifies Specify whether or not date/time interpretation is to be lenient. With lenient interpretation, a date such as "February 942, 1996" will be treated as being equivalent to the 941st day after February 1, 1996. With strict (non-lenient) interpretation, such dates will cause an exception to be thrown. The default is lenient.

Parameters:

lenient - true if the lenient mode is to be turned on; false if it is to be turned off.

See Also:

isLenient() DateFormat.setLenient(boolean) , DateFormat.setLenient(boolean)

isLenient

public boolean isLenient()

Tells Tell whether date/time interpretation is to be lenient.

Returns:

true if the interpretation mode of this calendar is lenient; false otherwise.

See Also:

setLenient(boolean)

setFirstDayOfWeek

public void setFirstDayOfWeek(int value)

Sets what the first day of the week is; e.g., SUNDAY Sunday in the U.S., MONDAY US, Monday in France.

Parameters:

value - the given first day of the week.

See Also:

#getFirstDayOfWeek(int), getMinimalDaysInFirstWeek()

getFirstDayOfWeek

public int getFirstDayOfWeek()

Gets what the first day of the week is; e.g., SUNDAY Sunday in the U.S., MONDAY US, Monday in France.

Returns:

the first day of the week.

See Also:

setFirstDayOfWeek(int) , getMinimalDaysInFirstWeek()

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 the 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:

getMinimalDaysInFirstWeek()

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 getMinimalDaysInFirstWeek returns 1. If the minimal days required must be a full week, this method getMinimalDaysInFirstWeek returns 7.

Returns:

the minimal days required in the first week of the year.

See Also:

setMinimalDaysInFirstWeek(int)

getMinimum

public abstract int getMinimum(int field)

Gets the minimum value for the given calendar time field. e.g., for Gregorian DAY_OF_MONTH, 1.

Parameters:

field - the given calendar time field.

Returns:

the minimum value for the given calendar field.

See Also:

getGreatestMinimum(int) , getActualMinimum(int) , getLeastMaximum(int) , getActualMaximum(int) , getMaximum(int) the minimum value for the given time field.

getMaximum

public abstract int getMaximum(int field)

Gets the maximum value for the given calendar time field. e.g. for Gregorian DAY_OF_MONTH, 31.

Parameters:

field - the given calendar time field.

Returns:

the maximum value for the given calendar field.

See Also:

getMinimum(int) , getGreatestMinimum(int) , getActualMinimum(int) , getLeastMaximum(int) , getActualMaximum(int) the maximum value for the given time field.

getGreatestMinimum

public abstract int getGreatestMinimum(int field)

Gets the highest minimum value for the given calendar field if varies. Otherwise same as getMinimum() . getMinimum(). For Gregorian, no difference.

Parameters:

field - the given calendar time field.

Returns:

the highest minimum value for the given calendar field.

See Also:

getActualMinimum(int) , getMaximum(int) , getLeastMaximum(int) , getActualMaximum(int) the highest minimum value for the given time field.

getLeastMaximum

public abstract int getLeastMaximum(int field)

Gets the lowest maximum value for the given calendar field if varies. Otherwise same as getMaximum() . getMaximum(). e.g., for the Gregorian calendar, DAY_OF_MONTH, 28.

Parameters:

field - the given calendar time field.

Returns:

the lowest maximum value for the given calendar field.

See Also:

getMinimum(int) , getGreatestMinimum(int) , getActualMinimum(int) , getActualMaximum(int) , getMaximum(int) the lowest maximum value for the given time field.

getActualMinimum

public int getActualMinimum(int field)

Returns Return the minimum value that the specified calendar this field could have, given the current date. For the Gregorian calendar, this is the same as getMinimum() getMinimum() and getGreatestMinimum() .

getGreatestMinimum(). The version of this function on Calendar uses an iterative algorithm to determine the actual minimum value for the calendar field. There is almost always a more efficient way to accomplish this (in most cases, you can simply return getMinimum() ). getMinimum()). GregorianCalendar overrides this function with a more efficient implementation.

Parameters:

field - the calendar field to determine the minimum of

Returns:

the minimum of the given calendar field for the current date of this Calendar

Since:

1.2

See Also:

getMinimum(int) , getActualMinimum(int) , getMaximum(int) , getLeastMaximum(int) , getActualMaximum(int)

getActualMaximum

public int getActualMaximum(int field)

Returns Return the maximum value that the specified calendar this field could have, given the current date. For example, with the date "Feb 3, 1997" and the DAY_OF_MONTH field in Gregorian, field, the actual maximum is would be 28; for "Feb 3, 1996" it is s 29. Similarly for a Hebrew calendar, for some years the actual maximum for MONTH is 11, 12, and for others 12.

13. The version of this function on Calendar uses an iterative algorithm to determine the actual maximum value for the field. There is almost always a more efficient way to accomplish this (in most cases, you can simply return getMaximum() ). getMaximum()). GregorianCalendar overrides this function with a more efficient implementation.

Parameters:

field - the calendar field to determine the maximum of

Returns:

the maximum of the given calendar field for the current date of this Calendar

Since:

1.2

See Also:

getMinimum(int) , getGreatestMinimum(int) , getActualMinimum(int) , getLeastMaximum(int) , getMaximum(int)

clone

public Object clone()

Creates and returns a copy of this object. Overrides Cloneable

Overrides:

clone in class Object

Returns:

a copy clone of this object. instance.

See Also:

Cloneable

toString

public String 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 be null.

Overrides:

toString in class Object

Returns:

a string representation of this calendar.