java.util
Class Calendar

java.lang.Object
  java.util.Calendar

All Implemented Interfaces:

Cloneable, Serializable

Direct Known Subclasses:

GregorianCalendar

public abstract class Calendar

extends Object

implements Serializable, Cloneable

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 for information about the Date class.)

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 time fields have been initialized with the current date and time:

 Calendar rightNow = Calendar.getInstance();
 

A Calendar object can produce all the 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 fields, as well as their meaning. For example, the first month of the year has value MONTH == JANUARY for all calendars. Other values are defined by the concrete subclass, such as ERA and YEAR. See individual field documentation and subclass documentation for details.

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.

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 when a Calendar is constructed. They may also be specified explicitly through the API.

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.

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.

 MONTH + DAY_OF_MONTH
 MONTH + WEEK_OF_MONTH + DAY_OF_WEEK
 MONTH + DAY_OF_WEEK_IN_MONTH + DAY_OF_WEEK
 DAY_OF_YEAR
 DAY_OF_WEEK + WEEK_OF_YEAR
 

For the time of day:

 HOUR_OF_DAY
 AM_PM + HOUR
 

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 methods

Calendar fields can be changed using three methods: set(), add(), and roll().

set(f, value) changes field f to value. In addition, it sets an internal member variable to indicate that field f has been changed. Although field f is changed immediately, the calendar's milliseconds is not recomputed until the next call to get(), getTime(), or getTimeInMillis() is made. Thus, multiple calls to set() do not trigger multiple, unnecessary computations. As a result of changing a field using set(), other fields may also change, depending on the field, the field value, and the calendar system. In addition, get(f) will not necessarily return value after the 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 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 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, 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

Author:

Mark Davis, David Goldsmith, Chen-Lieh Huang, Alan Liu

See Also:

Date, GregorianCalendar, TimeZone, DateFormat, Serialized Form

Field Summary

static int	AM Value of the 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 field indicating the fourth month of the year.
(package private) boolean	areAllFieldsSet True if all fields have been set.
protected boolean	areFieldsSet True if fields[] are in sync with the currently set time.
static int	AUGUST Value of the MONTH field indicating the eighth month of the year.
private static Hashtable	cachedLocaleData Cache to hold the firstDayOfWeek and minimalDaysInFirstWeek of a Locale.
(package private) static int	currentSerialVersion
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 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 field indicating the second month of the year.
static int	FIELD_COUNT The number of distinct fields recognized by get and set.
private static String[]	FIELD_NAME
protected int[]	fields The field values for the currently set time for this calendar.
private int	firstDayOfWeek The first day of the week, with possible values SUNDAY, MONDAY, etc.
static int	FRIDAY Value of the 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.
(package private) static int	INTERNALLY_SET
protected boolean[]	isSet The flags which tell if a specified 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 field indicating the first month of the year.
static int	JULY Value of the MONTH field indicating the seventh month of the year.
static int	JUNE Value of the MONTH field indicating the sixth month of the year.
private boolean	lenient True if this calendar allows out-of-range field values during computation of time from fields[].
static int	MARCH Value of the MONTH field indicating the third month of the year.
static int	MAY Value of the MONTH field indicating the fifth month of the year.
static int	MILLISECOND Field number for get and set indicating the millisecond within the second.
private int	minimalDaysInFirstWeek The number of days required for the first week in a month or year, with possible values from 1 to 7.
(package private) static int	MINIMUM_USER_STAMP
static int	MINUTE Field number for get and set indicating the minute within the hour.
static int	MONDAY Value of the DAY_OF_WEEK field indicating Monday.
static int	MONTH Field number for get and set indicating the month.
private int	nextStamp The next available value for stamp[], an internal array.
static int	NOVEMBER Value of the MONTH field indicating the eleventh month of the year.
static int	OCTOBER Value of the MONTH field indicating the tenth month of the year.
static int	PM Value of the AM_PM field indicating the period of the day from noon to just before midnight.
static int	SATURDAY Value of the 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 field indicating the ninth month of the year.
private int	serialVersionOnStream The version of the serialized data on the stream.
(package private) static long	serialVersionUID
(package private) int[]	stamp Pseudo-time-stamps which specify when each field was set.
static int	SUNDAY Value of the DAY_OF_WEEK field indicating Sunday.
static int	THURSDAY Value of the 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 field indicating Tuesday.
static int	UNDECIMBER Value of the MONTH field indicating the thirteenth month of the year.
(package private) static int	UNSET
static int	WEDNESDAY Value of the 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.
private TimeZone	zone The TimeZone used by this calendar.
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) Date Arithmetic function.
private void	adjustStamp() Adjusts the stamp[] values before nextStamp overflow. nextStamp is set to the next stamp value upon the return.
boolean	after(Object when) Compares the time field records.
boolean	before(Object when) Compares the time field records.
void	clear() Clears the values of all the time fields.
void	clear(int field) Clears the value in the given time field.
Object	clone() Overrides Cloneable
protected void	complete() Fills in any unset fields in the time field list.
protected abstract void	computeFields() Converts the current millisecond time value time to field values in fields[].
protected abstract void	computeTime() Converts the current field values in fields[] to the millisecond time value time.
private static Calendar	createCalendar(TimeZone zone, Locale aLocale)
boolean	equals(Object obj) Compares this calendar to the specified object.
int	get(int field) Gets the value for a given time field.
int	getActualMaximum(int field) Return the maximum value that this field could have, given the current date.
int	getActualMinimum(int field) Return the minimum value that this field could have, given the current date.
static Locale[]	getAvailableLocales() Gets the list of locales for which Calendars are installed.
int	getFirstDayOfWeek() Gets what the first day of the week is; e.g., Sunday in US, Monday in France.
abstract int	getGreatestMinimum(int field) Gets the highest minimum value for the given 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 field if varies.
abstract int	getMaximum(int field) Gets the maximum value for the given 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, getMinimalDaysInFirstWeek returns 1.
abstract int	getMinimum(int field) Gets the minimum value for the given time field.
Date	getTime() Gets this Calendar's current time.
long	getTimeInMillis() Gets this Calendar's current time as a long.
TimeZone	getTimeZone() Gets the time zone.
int	hashCode() Returns a hash code for this calendar.
(package private) void	internalClear(int field) Clears the value of the given calendar field and resets the field status flags only.
protected int	internalGet(int field) Gets the value for a given time field.
(package private) void	internalSet(int field, int value) Sets the value for the given time field.
private void	invalidateWeekFields() Invalidates the WEEK_OF_MONTH and WEEK_OF_YEAR fields if they have been calculated internally.
boolean	isLenient() Tell whether date/time interpretation is to be lenient.
boolean	isSet(int field) Determines if the given time field has a value set.
private void	readObject(ObjectInputStream stream) Reconstitute this object from a stream (i.e., deserialize it).
abstract void	roll(int field, boolean up) Time Field Rolling function.
void	roll(int field, int amount) Time Field Rolling function.
void	set(int field, int value) Sets the time field with the given value.
void	set(int year, int month, int date) Sets the values for the fields year, month, and date.
void	set(int year, int month, int date, int hour, int minute) Sets the values for the fields year, month, date, hour, and minute.
void	set(int year, int month, int date, int hour, int minute, int second) Sets the values for the fields year, month, date, hour, minute, and second.
void	setFirstDayOfWeek(int value) Sets what the first day of the week is; e.g., Sunday in US, Monday in France.
void	setLenient(boolean lenient) 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 the method with value 1.
void	setTime(Date 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.
private void	setWeekCountData(Locale desiredLocale) Both firstDayOfWeek and minimalDaysInFirstWeek are locale-dependent.
String	toString() Return a string representation of this calendar.
private void	updateTime() Recompute the time and update the status fields isTimeSet and areFieldsSet.
private void	writeObject(ObjectOutputStream stream) Save the state of this object to a stream (i.e., serialize it).

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

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. 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 field indicating Sunday.

See Also:

Constant Field Values

MONDAY

public static final int MONDAY

Value of the DAY_OF_WEEK field indicating Monday.

See Also:

Constant Field Values

TUESDAY

public static final int TUESDAY

Value of the DAY_OF_WEEK field indicating Tuesday.

See Also:

Constant Field Values

WEDNESDAY

public static final int WEDNESDAY

Value of the DAY_OF_WEEK field indicating Wednesday.

See Also:

Constant Field Values

THURSDAY

public static final int THURSDAY

Value of the DAY_OF_WEEK field indicating Thursday.

See Also:

Constant Field Values

FRIDAY

public static final int FRIDAY

Value of the DAY_OF_WEEK field indicating Friday.

See Also:

Constant Field Values

SATURDAY

public static final int SATURDAY

Value of the DAY_OF_WEEK field indicating Saturday.

See Also:

Constant Field Values

JANUARY

public static final int JANUARY

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

See Also:

Constant Field Values

FEBRUARY

public static final int FEBRUARY

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

See Also:

Constant Field Values

MARCH

public static final int MARCH

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

See Also:

Constant Field Values

APRIL

public static final int APRIL

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

See Also:

Constant Field Values

MAY

public static final int MAY

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

See Also:

Constant Field Values

JUNE

public static final int JUNE

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

See Also:

Constant Field Values

JULY

public static final int JULY

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

See Also:

Constant Field Values

AUGUST

public static final int AUGUST

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

See Also:

Constant Field Values

SEPTEMBER

public static final int SEPTEMBER

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

See Also:

Constant Field Values

OCTOBER

public static final int OCTOBER

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

See Also:

Constant Field Values

NOVEMBER

public static final int NOVEMBER

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

See Also:

Constant Field Values

DECEMBER

public static final int DECEMBER

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

See Also:

Constant Field Values

UNDECIMBER

public static final int UNDECIMBER

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

See Also:

Constant Field Values

fields

protected int[] fields

The 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 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.

stamp

transient int[] stamp

Pseudo-time-stamps which specify when each field was set. There are two special values, UNSET and INTERNALLY_SET. Values from MINIMUM_USER_SET to Integer.MAX_VALUE are legal user set values.

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.

areAllFieldsSet

transient boolean areAllFieldsSet

True if all fields have been set.

lenient

private boolean lenient

True if this calendar allows out-of-range field values during computation of time from fields[].

See Also:

setLenient(boolean)

zone

private TimeZone zone

The TimeZone used by this calendar. Calendar uses the time zone data to translate between locale and GMT time.

firstDayOfWeek

private int firstDayOfWeek

The first day of the week, with possible values SUNDAY, MONDAY, etc. This is a locale-dependent value.

minimalDaysInFirstWeek

private int minimalDaysInFirstWeek

The number of days required for the first week in a month or year, with possible values from 1 to 7. This is a locale-dependent value.

cachedLocaleData

private static Hashtable cachedLocaleData

Cache to hold the firstDayOfWeek and minimalDaysInFirstWeek of a Locale.

UNSET

static final int UNSET

See Also:

Constant Field Values

INTERNALLY_SET

static final int INTERNALLY_SET

See Also:

Constant Field Values

MINIMUM_USER_STAMP

static final int MINIMUM_USER_STAMP

See Also:

Constant Field Values

nextStamp

private int nextStamp

The next available value for stamp[], an internal array. This actually should not be written out to the stream, and will probably be removed from the stream in the near future. In the meantime, a value of MINIMUM_USER_STAMP should be used.

currentSerialVersion

static final int currentSerialVersion

See Also:

Constant Field Values

serialVersionOnStream

private int serialVersionOnStream

The version of the serialized data on the stream. Possible values:

0 or not present on stream

JDK 1.1.5 or earlier.

1

JDK 1.1.6 or later. Writes a correct 'time' value as well as compatible values for other fields. This is a transitional format.

When streaming out this class, the most recent format and the highest allowable serialVersionOnStream is written.

Since:

JDK1.1.6

serialVersionUID

static final long serialVersionUID

See Also:

Constant Field Values

FIELD_NAME

private static final String[] FIELD_NAME

Constructor Detail

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

Method Detail

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.

createCalendar

private static Calendar createCalendar(TimeZone zone,
                                       Locale aLocale)

getAvailableLocales

public static Locale[] getAvailableLocales()

Gets the list of locales for which Calendars are installed.

Returns:

the list of locales for which Calendars are installed.

computeTime

protected abstract void computeTime()

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

computeFields

protected abstract void computeFields()

Converts the current millisecond time value time to field values in fields[]. This allows you to sync up the 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 method.

See Also:

complete()

getTime

public final Date getTime()

Gets this Calendar's current time.

Returns:

the current time.

See Also:

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()

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(java.util.Date), getTimeInMillis()

get

public int get(int field)

Gets the value for a given time field.

Parameters:

field - the given time field.

Returns:

the value for the given time field.

Throws:

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

internalGet

protected final int internalGet(int field)

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

Parameters:

field - the given time field.

Returns:

the value for the given time field.

internalSet

final void internalSet(int field,
                       int value)

Sets the value for the given time field. This is an internal fast setter for subclasses. It does not affect the areFieldsSet, isTimeSet, or areAllFieldsSet flags.

internalClear

final void internalClear(int field)

Clears the value of the given calendar field and resets the field status flags only. The difference from clear(int) is that this method doesn't reset isTimeSet.

Parameters:

field - the given calendar field.

Throws:

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

set

public void set(int field,
                int value)

Sets the time field with the given value.

Parameters:

field - the given time field.

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

Throws:

ArrayIndexOutOfBoundsException - 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 fields year, month, and date. Previous values of other fields are retained. If this is not desired, call clear first.

Parameters:

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

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

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

set

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

Sets the values for the fields year, month, date, hour, and minute. Previous values of other fields are retained. If this is not desired, call clear first.

Parameters:

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

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

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

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

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

set

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

Sets the values for the fields year, month, date, hour, minute, and second. Previous values of other fields are retained. If this is not desired, call clear first.

Parameters:

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

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

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

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

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

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

clear

public final void clear()

Clears the values of all the time fields.

clear

public final void clear(int field)

Clears the value in the given time field.

Parameters:

field - the time field to be cleared.

isSet

public final boolean isSet(int field)

Determines if the given time field has a value set.

Returns:

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

complete

protected void complete()

Fills in any unset fields in the time field list.

equals

public boolean equals(Object obj)

Compares this calendar to the specified object. The result is true if and only if the argument is not null and is a Calendar object that represents the same calendar as this object.

Overrides:

equals in class Object

Parameters:

obj - the object to compare with.

Returns:

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)

Compares the time field records. Equivalent to comparing result of conversion to UTC.

Parameters:

when - the Calendar to be compared with this Calendar.

Returns:

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

after

public boolean after(Object when)

Compares the time field records. Equivalent to comparing result of conversion to UTC.

Parameters:

when - the Calendar to be compared with this Calendar.

Returns:

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

add

public abstract void add(int field,
                         int amount)

Date Arithmetic function. Adds the specified (signed) amount of time to the given 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.DATE, -5).

Parameters:

field - the time field.

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

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), set(int, int)

roll

public void roll(int field,
                 int amount)

Time Field Rolling function. Add to field a signed amount without changing larger fields. A negative roll amount means to roll down. [NOTE: This default implementation on Calendar just repeatedly calls the version of 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 time field.

amount - the signed amount to add to field.

Since:

1.2

See Also:

add(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)

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 interpretation, such dates will cause an exception to be thrown.

See Also:

DateFormat.setLenient(boolean)

isLenient

public boolean isLenient()

Tell whether date/time interpretation is to be lenient.

setFirstDayOfWeek

public void setFirstDayOfWeek(int value)

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

Parameters:

value - the given first day of the week.

getFirstDayOfWeek

public int getFirstDayOfWeek()

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

Returns:

the first day of the week.

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 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.

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

Returns:

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

getMinimum

public abstract int getMinimum(int field)

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

Parameters:

field - the given time field.

Returns:

the minimum value for the given time field.

getMaximum

public abstract int getMaximum(int field)

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

Parameters:

field - the given time field.

Returns:

the maximum value for the given time field.

getGreatestMinimum

public abstract int getGreatestMinimum(int field)

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

Parameters:

field - the given time field.

Returns:

the highest minimum value for the given time field.

getLeastMaximum

public abstract int getLeastMaximum(int field)

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

Parameters:

field - the given time field.

Returns:

the lowest maximum value for the given time field.

getActualMinimum

public int getActualMinimum(int field)

Return the minimum value that this field could have, given the current date. For the Gregorian calendar, this is the same as getMinimum() and getGreatestMinimum(). The version of this function on Calendar uses an iterative algorithm to determine the actual minimum value for the field. There is almost always a more efficient way to accomplish this (in most cases, you can simply return getMinimum()). GregorianCalendar overrides this function with a more efficient implementation.

Parameters:

field - the field to determine the minimum of

Returns:

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

Since:

1.2

getActualMaximum

public int getActualMaximum(int field)

Return the maximum value that this field could have, given the current date. For example, with the date "Feb 3, 1997" and the DAY_OF_MONTH field, the actual maximum would be 28; for "Feb 3, 1996" it s 29. Similarly for a Hebrew calendar, for some years the actual maximum for MONTH is 12, and for others 13. 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()). GregorianCalendar overrides this function with a more efficient implementation.

Parameters:

field - the field to determine the maximum of

Returns:

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

Since:

1.2

clone

public Object clone()

Overrides Cloneable

Overrides:

clone in class Object

Returns:

a clone of this 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.

setWeekCountData

private void setWeekCountData(Locale desiredLocale)

Both firstDayOfWeek and minimalDaysInFirstWeek are locale-dependent. They are used to figure out the week count for a specific date for a given locale. These must be set when a Calendar is constructed.

Parameters:

desiredLocale - the given locale.

updateTime

private void updateTime()

Recompute the time and update the status fields isTimeSet and areFieldsSet. Callers should check isTimeSet and only call this method if isTimeSet is false.

adjustStamp

private final void adjustStamp()

Adjusts the stamp[] values before nextStamp overflow. nextStamp is set to the next stamp value upon the return.

invalidateWeekFields

private void invalidateWeekFields()

Invalidates the WEEK_OF_MONTH and WEEK_OF_YEAR fields if they have been calculated internally.

writeObject

private void writeObject(ObjectOutputStream stream)
                  throws IOException

Save the state of this object to a stream (i.e., serialize it). Ideally, Calendar would only write out its state data and the current time, and not write any field data out, such as fields[], isTimeSet, areFieldsSet, and isSet[]. nextStamp also should not be part of the persistent state. Unfortunately, this didn't happen before JDK 1.1 shipped. To be compatible with JDK 1.1, we will always have to write out the field values and state flags. However, nextStamp can be removed from the serialization stream; this will probably happen in the near future.

Throws:

IOException

readObject

private void readObject(ObjectInputStream stream)
                 throws IOException,
                        ClassNotFoundException

Reconstitute this object from a stream (i.e., deserialize it).

Throws:

IOException

ClassNotFoundException