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java.util
Class Calendar

java.lang.Object
  java.util.Calendar

public abstract class Calendar

extends Object

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.

Like other locale-sensitive classes, Calendar provides a class method, getInstance, for getting a generally useful object of this type.

 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).

When computing a Date from time fields, there may be insufficient information to compute the Date (such as only year and month but no day in the month).

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. Note: The ambiguity in interpretation of what day midnight belongs to, is resolved as so: midnight "belongs" to the following day.
23:59 on Dec 31, 1969 < 00:00 on Jan 1, 1970.
12:00 PM is midday, and 12:00 AM is midnight.
11:59 PM on Jan 1 < 12:00 AM on Jan 2 < 12:01 AM on Jan 2.
11:59 AM on Mar 10 < 12:00 PM on Mar 10 < 12:01 PM on Mar 10.
24:00 or greater are invalid. Hours greater than 12 are invalid in AM/PM mode. Setting the time will never change the date.

If equivalent times are entered in AM/PM or 24 hour mode, equality will be determined by the actual time rather than the entered time.

This class has been subset for J2ME based on the JDK 1.3 Calendar class. Many methods and variables have been pruned, and other methods simplified, in an effort to reduce the size of this class.

See Also:

Date, TimeZone

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.
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	DECEMBER Value of the MONTH field indicating the twelfth month of the year.
static int	FEBRUARY Value of the MONTH field indicating the second month of the year.
protected int[]	fields The 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 time field for the calendar is set.
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	WEDNESDAY Value of the DAY_OF_WEEK field indicating Wednesday.
static int	YEAR Field number for get and set indicating the year.

Constructor Summary

protected

Calendar() Constructs a Calendar with the default time zone.

Method Summary

boolean	after(Object when) Compares the time field records.
boolean	before(Object when) Compares the time field records.
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.
boolean	equals(Object obj) Compares this calendar to the specified object.
int	get(int field) Gets the value for a given time field.
static Calendar	getInstance() Gets a calendar using the default time zone.
static Calendar	getInstance(TimeZone zone) Gets a calendar using the specified time zone.
Date	getTime() Gets this Calendar's current time.
protected long	getTimeInMillis() Gets this Calendar's current time as a long expressed in milliseconds after January 1, 1970, 0:00:00 GMT (the epoch).
TimeZone	getTimeZone() Gets the time zone.
void	set(int field, int value) Sets the time field with the given value.
void	setTime(Date date) Sets this Calendar's current time with the given Date.
protected 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.

Methods inherited from class java.lang.Object

getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

YEAR

public static final int YEAR

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

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.

See Also:

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.

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.

See Also:

DATE, 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.

See Also:

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:

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

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

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.

isSet

protected boolean[] isSet

The flags which tell if a specified time field for the calendar is set. This is an array of FIELD_COUNT booleans,

time

protected long time

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

Constructor Detail

Calendar

protected Calendar()

Constructs a Calendar with the default time zone.

See Also:

TimeZone.getDefault()

Method Detail

getTime

public final Date getTime()

Gets this Calendar's current time.

Returns:

the current time.

See Also:

setTime(java.util.Date)

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()

getInstance

public static Calendar getInstance()

Gets a calendar using the default time zone.

Returns:

a Calendar.

getInstance

public static Calendar getInstance(TimeZone zone)

Gets a calendar using the specified time zone.

Parameters:

zone - the time zone to use

Returns:

a Calendar.

getTimeInMillis

protected long getTimeInMillis()

Gets this Calendar's current time as a long expressed in milliseconds after January 1, 1970, 0:00:00 GMT (the epoch).

Returns:

the current time as UTC milliseconds from the epoch.

See Also:

setTimeInMillis(long)

setTimeInMillis

protected 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:

getTimeInMillis()

get

public final int get(int field)

Gets the value for a given time field.

Parameters:

field - the given time field (either YEAR, MONTH, DATE, DAY_OF_WEEK, HOUR_OF_DAY, HOUR, AM_PM, MINUTE, SECOND, or MILLISECOND

Returns:

the value for the given time field.

Throws:

ArrayIndexOutOfBoundsException - if the parameter is not one of the above.

set

public final 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 an illegal field parameter is received.

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:

Boolean.hashCode(), 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.

setTimeZone

public void setTimeZone(TimeZone value)

Sets the time zone with the given time zone value.

Parameters:

value - the given time zone.

See Also:

getTimeZone()

getTimeZone

public TimeZone getTimeZone()

Gets the time zone.

Returns:

the time zone object associated with this calendar.

See Also:

setTimeZone(java.util.TimeZone)

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.

computeTime

protected abstract void computeTime()

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