java.util
Class Calendar

java.lang.Object
  java.util.Calendar

All Implemented Interfaces:

Serializable, Cloneable, Comparable<Calendar>

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 such as YEAR, MONTH, DAY_OF_MONTH, HOUR, and so on, and for manipulating the calendar fields, such as getting the date of the next week. An instant in time can be represented by a millisecond value that is an offset from the Epoch, January 1, 1970 00:00:00.000 GMT (Gregorian).

The class also provides additional fields and methods for implementing a concrete calendar system outside the package. Those fields and methods are defined as protected.

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

     Calendar rightNow = Calendar.getInstance();
 

A Calendar object can produce all the calendar field values needed to implement the date-time formatting for a particular language and calendar style (for example, Japanese-Gregorian, Japanese-Traditional). Calendar defines the range of values returned by certain calendar fields, as well as their meaning. For example, the first month of the calendar system has value MONTH == JANUARY for all calendars. Other values are defined by the concrete subclass, such as ERA. See individual field documentation and subclass documentation for details.

Getting and Setting Calendar Field Values

The calendar field values can be set by calling the set methods. Any field values set in a Calendar will not be interpreted until it needs to calculate its time value (milliseconds from the Epoch) or values of the calendar fields. Calling the get, getTimeInMillis, getTime, add and roll involves such calculation.

Leniency

Calendar has two modes for interpreting the calendar fields, lenient and non-lenient. When a Calendar is in lenient mode, it accepts a wider range of calendar field values than it produces. When a Calendar recomputes calendar field values for return by get(), all of the calendar fields are normalized. For example, a lenient GregorianCalendar interprets MONTH == JANUARY, DAY_OF_MONTH == 32 as February 1.

When a Calendar is in non-lenient mode, it throws an exception if there is any inconsistency in its calendar fields. For example, a GregorianCalendar always produces DAY_OF_MONTH values between 1 and the length of the month. A non-lenient GregorianCalendar throws an exception upon calculating its time or calendar field values if any out-of-range field value has been set.

First Week

Calendar defines a locale-specific seven day week using two parameters: the first day of the week and the minimal days in first week (from 1 to 7). These numbers are taken from the locale resource data when a Calendar is constructed. They may also be specified explicitly through the methods for setting their values.

When setting or getting the WEEK_OF_MONTH or WEEK_OF_YEAR fields, Calendar must determine the first week of the month or year as a reference point. The first week of a month or year is defined as the earliest seven day period beginning on getFirstDayOfWeek() and containing at least getMinimalDaysInFirstWeek() days of that month or year. Weeks numbered ..., -1, 0 precede the first week; weeks numbered 2, 3,... follow it. Note that the normalized numbering returned by get() may be different. For example, a specific Calendar subclass may designate the week before week 1 of a year as week n of the previous year.

Calendar Fields Resolution

When computing a date and time from the calendar fields, there may be insufficient information for the computation (such as only year and month with no day of month), or there may be inconsistent information (such as Tuesday, July 15, 1996 (Gregorian) -- July 15, 1996 is actually a Monday). Calendar will resolve calendar field values to determine the date and time in the following way.

If there is any conflict in calendar field values, Calendar gives priorities to calendar fields that have been set more recently. The following are the default combinations of the calendar fields. The most recent combination, as determined by the most recently set single field, will be used.

For the 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
 

For the time of day fields:

 HOUR_OF_DAY
 AM_PM + HOUR
 

If there are any calendar fields whose values haven't been set in the selected field combination, Calendar uses their default values. The default value of each field may vary by concrete calendar systems. For example, in GregorianCalendar, the default of a field is the same as that of the start of the Epoch: i.e., YEAR = 1970, MONTH = JANUARY, DAY_OF_MONTH = 1, etc.

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

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

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

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

Example: Consider a GregorianCalendar originally set to August 31, 1999. Calling set(Calendar.MONTH, Calendar.SEPTEMBER) sets the date to September 31, 1999. This is a temporary internal representation that resolves to October 1, 1999 if getTime()is then called. However, a call to set(Calendar.DAY_OF_MONTH, 30) before the call to getTime() sets the date to September 30, 1999, since no recomputation occurs after set() itself.

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

Add rule 1. The value of field 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, 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, 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.
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.
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.
protected int[]	fields The calendar field values for the currently set time for this calendar.
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.
protected boolean[]	isSet The flags which tell if a specified calendar 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.
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.
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.
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.
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.
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.
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.
boolean	after(Object when) Returns whether this Calendar represents a time after the time represented by the specified Object.
boolean	before(Object when) Returns whether this Calendar represents a time before the time represented by the specified Object.
void	clear() Sets all the calendar field values and the time value (millisecond offset from the Epoch) of this Calendar undefined.
void	clear(int field) Sets the given calendar field value and the time value (millisecond offset from the Epoch) of this Calendar undefined.
Object	clone() Creates and returns a copy of this object.
int	compareTo(Calendar anotherCalendar) Compares the time values (millisecond offsets from the Epoch) represented by two Calendar objects.
protected void	complete() Fills in any unset fields in the calendar fields.
protected abstract void	computeFields() Converts the current millisecond time value time to calendar field values in fields[].
protected abstract void	computeTime() Converts the current calendar field values in fields[] to the millisecond time value time.
boolean	equals(Object obj) Compares this Calendar to the specified Object.
int	get(int field) Returns the value of the given calendar field.
int	getActualMaximum(int field) Returns the maximum value that the specified calendar field could have, given the time value of this Calendar.
int	getActualMinimum(int field) Returns the minimum value that the specified calendar field could have, given the time value of this Calendar.
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 the U.S., MONDAY in France.
abstract int	getGreatestMinimum(int field) Returns the highest minimum value for the given calendar field of this Calendar instance.
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) Returns the lowest maximum value for the given calendar field of this Calendar instance.
abstract int	getMaximum(int field) Returns the maximum value for the given calendar field of this Calendar instance.
int	getMinimalDaysInFirstWeek() Gets what the minimal days required in the first week of the year are; e.g., if the first week is defined as one that contains the first day of the first month of a year, this method returns 1.
abstract int	getMinimum(int field) Returns the minimum value for the given calendar field of this Calendar instance.
Date	getTime() Returns a Date object representing this Calendar's time value (millisecond offset from the Epoch").
long	getTimeInMillis() Returns this Calendar's time value in milliseconds.
TimeZone	getTimeZone() Gets the time zone.
int	hashCode() Returns a hash code for this calendar.
protected int	internalGet(int field) Returns the value of the given calendar field.
boolean	isLenient() Tells whether date/time interpretation is to be lenient.
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.
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.
void	roll(int field, int amount) Adds the specified (signed) amount to the specified calendar field without changing larger fields.
void	set(int field, int value) Sets the given calendar field to the given value.
void	set(int year, int month, int date) Sets the values for the calendar fields YEAR, MONTH, and DAY_OF_MONTH.
void	set(int year, int month, int date, int hourOfDay, int minute) Sets the values for the calendar fields YEAR, MONTH, DAY_OF_MONTH, HOUR_OF_DAY, and MINUTE.
void	set(int year, int month, int date, int hourOfDay, int minute, int second) Sets the values for the fields YEAR, MONTH, DAY_OF_MONTH, HOUR, MINUTE, and SECOND.
void	setFirstDayOfWeek(int value) Sets what the first day of the week is; e.g., SUNDAY in the U.S., MONDAY in France.
void	setLenient(boolean lenient) Specifies 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 method with value 1.
void	setTime(Date date) Sets this Calendar's 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

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. 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 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 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.

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.

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.

Returns:

An array of locales for which localized Calendar instances are available.

computeTime

protected abstract void computeTime()

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

See Also:

complete(), computeFields()

computeFields

protected abstract void computeFields()

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

See Also:

computeTime()

getTime

public final Date getTime()

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

Returns:

a Date representing the time value.

See Also:

setTime(Date), getTimeInMillis()

setTime

public final void setTime(Date date)

Sets this Calendar's 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.

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), 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.

Parameters:

field - the given calendar field.

Returns:

the value for the given calendar field.

Throws:

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

See Also:

set(int,int), complete()

internalGet

protected final int internalGet(int field)

Returns the value of the given calendar field. This method does not involve normalization or validation of the field value.

Parameters:

field - the given calendar field.

Returns:

the value for the given calendar field.

See Also:

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.

Parameters:

field - the given calendar field.

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

Throws:

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

See Also:

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

set

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

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

Parameters:

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

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

date - the value used to set the DAY_OF_MONTH calendar 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 minute)

Sets the values for the calendar fields YEAR, MONTH, DAY_OF_MONTH, HOUR_OF_DAY, 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 calendar field.

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

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

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

minute - the value used to set the MINUTE calendar 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 minute,
                      int second)

Sets the values for the fields YEAR, MONTH, DAY_OF_MONTH, 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 calendar field.

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

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

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

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

second - the value used to set the SECOND calendar 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.

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.

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 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.

Returns:

true if the given calendar 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.

equals

public boolean equals(Object obj)

Compares this Calendar to the specified Object. The result is true if and only if the argument 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 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.

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.

Parameters:

when - the Object to be compared

Returns:

true if the time of this Calendar is before the time represented by 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.

Parameters:

when - the Object to be compared

Returns:

true if the time of this Calendar is after the time represented by 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.

Specified by:

compareTo in interface Comparable<Calendar>

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)

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

add(Calendar.DAY_OF_MONTH, -5).

Parameters:

field - the calendar field.

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

See Also:

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

roll

public abstract void roll(int field,
                          boolean up)

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

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

Parameters:

field - the time field.

up - indicates if the value of the specified time field is to be rolled up or rolled down. Use true if rolling up, false otherwise.

See Also:

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

roll

public void roll(int field,
                 int amount)

Adds the specified (signed) amount to the specified calendar field without changing larger fields. A negative amount means to roll down.

NOTE: This default implementation on Calendar just repeatedly calls the version of roll() that 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 field.

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

Since:

1.2

See Also:

roll(int,boolean), 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)

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

Parameters:

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

See Also:

isLenient(), DateFormat.setLenient(boolean)

isLenient

public boolean isLenient()

Tells 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 in the U.S., MONDAY in France.

Parameters:

value - the given first day of the week.

See Also:

getFirstDayOfWeek(), getMinimalDaysInFirstWeek()

getFirstDayOfWeek

public int getFirstDayOfWeek()

Gets what the first day of the week is; e.g., SUNDAY in the U.S., 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 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 returns 1. If the minimal days required must be a full week, this method returns 7.

Returns:

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

See Also:

setMinimalDaysInFirstWeek(int)

getMinimum

public abstract int getMinimum(int field)

Returns the minimum value for the given calendar field of this Calendar instance. The minimum value is defined as the smallest value returned by the get method for any possible time value. The minimum value depends on calendar system specific parameters of the instance.

Parameters:

field - the calendar field.

Returns:

the minimum value for the given calendar field.

See Also:

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

getMaximum

public abstract int getMaximum(int field)

Returns the maximum value for the given calendar field of this Calendar instance. The maximum value is defined as the largest value returned by the get method for any possible time value. The maximum value depends on calendar system specific parameters of the instance.

Parameters:

field - the calendar field.

Returns:

the maximum value for the given calendar field.

See Also:

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

getGreatestMinimum

public abstract int getGreatestMinimum(int field)

Returns the highest minimum value for the given calendar field of this Calendar instance. The highest minimum value is defined as the largest value returned by getActualMinimum(int) for any possible time value. The greatest minimum value depends on calendar system specific parameters of the instance.

Parameters:

field - the calendar field.

Returns:

the highest minimum value for the given calendar field.

See Also:

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

getLeastMaximum

public abstract int getLeastMaximum(int field)

Returns the lowest maximum value for the given calendar field of this Calendar instance. The lowest maximum value is defined as the smallest value returned by getActualMaximum(int) for any possible time value. The least maximum value depends on calendar system specific parameters of the instance. For example, a Calendar for the Gregorian calendar system returns 28 for the DAY_OF_MONTH field, because the 28th is the last day of the shortest month of this calendar, February in a common year.

Parameters:

field - the calendar field.

Returns:

the lowest maximum value for the given calendar field.

See Also:

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

getActualMinimum

public int getActualMinimum(int field)

Returns the minimum value that the specified calendar field could have, given the time value of this Calendar.

The default implementation of this method uses an iterative algorithm to determine the actual minimum value for the calendar field. Subclasses should, if possible, override this with a more efficient implementation - in many cases, they can simply return getMinimum().

Parameters:

field - the calendar field

Returns:

the minimum of the given calendar field for the time value of this Calendar

Since:

1.2

See Also:

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

getActualMaximum

public int getActualMaximum(int field)

Returns the maximum value that the specified calendar field could have, given the time value of this Calendar. For example, the actual maximum value of the MONTH field is 12 in some years, and 13 in other years in the Hebrew calendar system.

The default implementation of this method uses an iterative algorithm to determine the actual maximum value for the calendar field. Subclasses should, if possible, override this with a more efficient implementation.

Parameters:

field - the calendar field

Returns:

the maximum of the given calendar field for the time value of this Calendar

Since:

1.2

See Also:

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

clone

public Object clone()

Creates and returns a copy of this object.

Overrides:

clone in class Object

Returns:

a copy of this object.

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.