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public abstract class java.util.Calendar

(source file: Calendar.java)
java.lang.Object
   |
   +----java.util.Calendar
The pure class interface. 
public abstract class Calendar
  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 java.util.Date for information about the Date class.)

Subclasses of Calendar interpret a Date according to the rules of a specific calendar system. The JDK 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 GregorianCalendar 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).

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 historial 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. 24:00:00 "belongs" to the following day. That is, 23:59 on Dec 31, 1969 < 24:00 on Jan 1, 1970 < 24:01:00 on Jan 1, 1970
  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 java.text.DateFormat to format dates.

Calendar provides an API for field "rolling", where fields can be incremented or decremented, but wrap around. For example, rolling the month up in the date "September 12, 1996" results in "October 12, 1996".

Calendar also provides a date arithmetic function for adding the specified (signed) amount of time to a particular time field. For example, subtracting 5 days from the date "September 12, 1996" results in "September 7, 1996".

See also:
Date, GregorianCalendar, TimeZone, java.text.DateFormat

Constuctor Index

O Calendar(TimeZone, Locale)
Constructs a Calendar with the given time zone and locale.
O Calendar()
Constructs a Calendar with the default time zone as returned by TimeZone.getDefault(), and

Variables Index

O AM
Useful constant for hour in 12-hour clock
O AM_PM
Useful constant for date and time
O APRIL
Useful constant for month
O AUGUST
Useful constant for month
O DATE
Useful constant for date and time
O DAY_OF_MONTH
Useful constant for date and time
O DAY_OF_WEEK
Useful constant for date and time
O DAY_OF_WEEK_IN_MONTH
Useful constant for date and time
O DAY_OF_YEAR
Useful constant for date and time
O DECEMBER
Useful constant for month
O DST_OFFSET
Useful constant for date and time
O ERA
Useful constant for date and time
O FEBRUARY
Useful constant for month
O FIELD_COUNT
Useful constant for date and time. FIELD_COUNT is used for the time field array creation.
O FRIDAY
Useful constant for days of week
O HOUR
Useful constant for date and time
O HOUR_OF_DAY
Useful constant for date and time
O JANUARY
Useful constant for month
O JULY
Useful constant for month
O JUNE
Useful constant for month
O MARCH
Useful constant for month
O MAY
Useful constant for month
O MILLISECOND
Useful constant for date and time
O MINUTE
Useful constant for date and time
O MONDAY
Useful constant for days of week
O MONTH
Useful constant for date and time
O NOVEMBER
Useful constant for month
O OCTOBER
Useful constant for month
O PM
Useful constant for hour in 12-hour clock
O SATURDAY
Useful constant for days of week
O SECOND
Useful constant for date and time
O SEPTEMBER
Useful constant for month
O SUNDAY
Useful constant for days of week
O THURSDAY
Useful constant for days of week
O TUESDAY
Useful constant for days of week
O UNDECIMBER
Useful constant for month
O WEDNESDAY
Useful constant for days of week
O WEEK_OF_MONTH
Useful constant for date and time
O WEEK_OF_YEAR
Useful constant for date and time
O YEAR
Useful constant for date and time
O ZONE_OFFSET
Useful constant for date and time
O areFieldsSet
True if the fields are in sync with the currently set time of this Calendar. If false, then
O fields
The time fields containing values into which the millis is computed.
O isSet
The flags which tell if a specified time field for the calendar is set. A new object has no
O isTimeSet
The flag which indicates if the current time is set for the calendar. The time is made
O time
The current time set for the calendar.

Methods

O add(int, int)
Date Arithmetic function. Adds the specified (signed) amount of time to the given time
O after(Object)
Compares the time field records. Equivalent to comparing result of conversion to UTC.
O before(Object)
Compares the time field records. Equivalent to comparing result of conversion to UTC.
O clear(int)
Clears the value in the given time field.
O clear()
Clears the values of all the time fields.
O clone()
Overrides Cloneable
O complete()
Fills in any unset fields in the time field list.
O computeFields()
Converts UTC as milliseconds to time field values. This allows you to sync up the time
O computeTime()
Converts Calendar's time field values to UTC as milliseconds.
O equals(Object)
Compares this calendar to the specified object. The result is true if and only
O get(int)
Gets the value for a given time field.
O getAvailableLocales()
Gets the set of locales for which Calendars are installed.
O getFirstDayOfWeek()
Gets what the first day of the week is; e.g., Sunday in US, Monday in France.
O getGreatestMinimum(int)
Gets the highest minimum value for the given field if varies. Otherwise same as getMinimum()
O getInstance(Locale)
Gets a Calendar using the default timezone and given locale.
O getInstance(TimeZone, Locale)
Gets a Calendar using the given timezone and given locale.
O getInstance(TimeZone)
Gets a Calendar using the given timezone and default locale.
O getInstance()
Gets a Calendar using the default timezone and locale.
O getLeastMaximum(int)
Gets the lowest maximum value for the given field if varies. Otherwise same as getMaximum()
O getMaximum(int)
Gets the maximum value for the given time field. e.g
O getMinimalDaysInFirstWeek()
Gets what the minimal days required in the first week of the year are; e.g., if the first
O getMinimum(int)
Gets the minimum value for the given time field. e.g., for Gregorian DAY_OF_MONTH, 1.
O getTime()
Gets this Calendar's current time.
O getTimeInMillis()
Gets this Calendar's current time as a long.
O getTimeZone()
Gets the time zone.
O internalGet(int)
Gets the value for a given time field
O isLenient()
Tell whether date/time interpretation is to be lenient.
O isSet(int)
Determines if the given time field has a value set.
O roll(int, int)
Time Field Rolling function. Rolls up or down the specified number of units on the given
O roll(int, boolean)
Time Field Rolling function. Rolls (up/down) a single unit of time on the given time field
O set(int, int, int, int, int, int)
Sets the values for the fields year, month, date, hour, minute, and second. Previous values
O set(int, int, int, int, int)
Sets the values for the fields year, month, date, hour, and minute. Previous values of
O set(int, int, int)
Sets the values for the fields year, month, and date. Previous values of other fields are
O set(int, int)
Sets the time field with the given value.
O setFirstDayOfWeek(int)
Sets what the first day of the week is; e.g., Sunday in US, Monday in France.
O setLenient(boolean)
Specify whether or not date/time interpretation is to be lenient
O setMinimalDaysInFirstWeek(int)
Sets what the minimal days required in the first week of the year are; For example, if the
O setTime(Date)
Sets this Calendar's current time with the given Date.
O setTimeInMillis(long)
Sets this Calendar's current time from the given long value.
O setTimeZone(TimeZone)
Sets the time zone with the given time zone value.
O toString()
Return a string representation of this calendar.

Constructors

O Calendar
protected Calendar();
Constructs a Calendar with the default time zone as returned by TimeZone.getDefault(), and the default locale.

See also:
getDefault

O Calendar

protected Calendar(TimeZone zone,
                   Locale aLocale);
Constructs a Calendar with the given time zone and locale.

Parameters:
zone - the given time zone.

Variables

O ERA
public static final int ERA;
Useful constant for date and time. Used in time fields. ERA is calendar specific.

O YEAR

public static final int YEAR;
Useful constant for date and time. Used in time fields.

O MONTH

public static final int MONTH;
Useful constant for date and time. Used in time fields.

O WEEK_OF_YEAR

public static final int WEEK_OF_YEAR;
Useful constant for date and time. Used in time fields.

O WEEK_OF_MONTH

public static final int WEEK_OF_MONTH;
Useful constant for date and time. Used in time fields.

O DATE

public static final int DATE;
Useful constant for date and time. Used in time fields. This is a synonym for DAY_OF_MONTH.

O DAY_OF_MONTH

public static final int DAY_OF_MONTH;
Useful constant for date and time. Used in time fields. This is a synonym for DATE.

O DAY_OF_YEAR

public static final int DAY_OF_YEAR;
Useful constant for date and time. Used in time fields.

O DAY_OF_WEEK

public static final int DAY_OF_WEEK;
Useful constant for date and time. Used in time fields.

O DAY_OF_WEEK_IN_MONTH

public static final int DAY_OF_WEEK_IN_MONTH;
Useful constant for date and time. Used in time fields.

O AM_PM

public static final int AM_PM;
Useful constant for date and time. Used in time fields.

O HOUR

public static final int HOUR;
Useful constant for date and time. Used in time fields. HOUR is used for the 12-hour clock.

O HOUR_OF_DAY

public static final int HOUR_OF_DAY;
Useful constant for date and time. Used in time fields. HOUR_OF_DAY is used for the 24-hour clock.

O MINUTE

public static final int MINUTE;
Useful constant for date and time. Used in time fields.

O SECOND

public static final int SECOND;
Useful constant for date and time. Used in time fields.

O MILLISECOND

public static final int MILLISECOND;
Useful constant for date and time. Used in time fields.

O ZONE_OFFSET

public static final int ZONE_OFFSET;
Useful constant for date and time. Used in time fields.

O DST_OFFSET

public static final int DST_OFFSET;
Useful constant for date and time. Used in time fields.

O FIELD_COUNT

public static final int FIELD_COUNT;
Useful constant for date and time. FIELD_COUNT is used for the time field array creation.

O SUNDAY

public static final int SUNDAY;
Useful constant for days of week. Used in GregorianCalendar.

O MONDAY

public static final int MONDAY;
Useful constant for days of week. Used in GregorianCalendar.

O TUESDAY

public static final int TUESDAY;
Useful constant for days of week. Used in GregorianCalendar.

O WEDNESDAY

public static final int WEDNESDAY;
Useful constant for days of week. Used in GregorianCalendar.

O THURSDAY

public static final int THURSDAY;
Useful constant for days of week. Used in GregorianCalendar.

O FRIDAY

public static final int FRIDAY;
Useful constant for days of week. Used in GregorianCalendar.

O SATURDAY

public static final int SATURDAY;
Useful constant for days of week. Used in GregorianCalendar.

O JANUARY

public static final int JANUARY;
Useful constant for month. Used in GregorianCalendar. Note: Calendar month is now 0-based.

O FEBRUARY

public static final int FEBRUARY;
Useful constant for month. Used in GregorianCalendar.

O MARCH

public static final int MARCH;
Useful constant for month. Used in GregorianCalendar.

O APRIL

public static final int APRIL;
Useful constant for month. Used in GregorianCalendar.

O MAY

public static final int MAY;
Useful constant for month. Used in GregorianCalendar.

O JUNE

public static final int JUNE;
Useful constant for month. Used in GregorianCalendar.

O JULY

public static final int JULY;
Useful constant for month. Used in GregorianCalendar.

O AUGUST

public static final int AUGUST;
Useful constant for month. Used in GregorianCalendar.

O SEPTEMBER

public static final int SEPTEMBER;
Useful constant for month. Used in GregorianCalendar.

O OCTOBER

public static final int OCTOBER;
Useful constant for month. Used in GregorianCalendar.

O NOVEMBER

public static final int NOVEMBER;
Useful constant for month. Used in GregorianCalendar.

O DECEMBER

public static final int DECEMBER;
Useful constant for month. Used in GregorianCalendar.

O UNDECIMBER

public static final int UNDECIMBER;
Useful constant for month. Used in GregorianCalendar. UNDECIMBER is an artifical name. This 13th month is for lunar calendars.

O AM

public static final int AM;
Useful constant for hour in 12-hour clock. Used in GregorianCalendar.

O PM

public static final int PM;
Useful constant for hour in 12-hour clock. Used in GregorianCalendar.

O fields

protected int[] fields;
The time fields containing values into which the millis is computed.

O 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.

O time

protected long time;
The current time set for the calendar.

O isTimeSet

protected boolean isTimeSet;
The flag which indicates if the current time is set for the calendar. The time is made invalid by the user setting an individual field.

O areFieldsSet

protected boolean areFieldsSet;
True if the fields are in sync with the currently set time of this Calendar. 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 the time field. This should really be named areFieldsInSync, but the old name is retained for backward compatibility.

Methods

O getInstance
public static synchronized Calendar getInstance();
Gets a Calendar using the default timezone and locale.

Returns:
a Calendar.

O getInstance

public static synchronized Calendar getInstance(TimeZone zone);
Gets a Calendar using the given timezone and default locale.

Parameters:
zone - the given timezone.
Returns:
a Calendar.

O getInstance

public static synchronized Calendar getInstance(Locale aLocale);
Gets a Calendar using the default timezone and given locale.

Parameters:
aLocale - the given locale.
Returns:
a Calendar.

O getInstance

public static synchronized Calendar getInstance(TimeZone zone,
                                                Locale aLocale);
Gets a Calendar using the given timezone and given locale.

Parameters:
zone - the given timezone.
aLocale - the given locale.
Returns:
a Calendar.

O getAvailableLocales

public static synchronized Locale[] getAvailableLocales();
Gets the set of locales for which Calendars are installed.

Returns:
the set of locales for which Calendars are installed.

O computeTime

protected abstract void computeTime();
Converts Calendar's time field values to UTC as milliseconds.

O computeFields

protected abstract void computeFields();
Converts UTC as milliseconds to time field values. 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

O getTime

public final Date getTime();
Gets this Calendar's current time.

Returns:
the current time.

O setTime

public final void setTime(Date date);
Sets this Calendar's current time with the given Date.

Parameters:
date - the given Date.

O getTimeInMillis

protected long getTimeInMillis();
Gets this Calendar's current time as a long.

Returns:
the current time as UTC milliseconds from the epoch.

O setTimeInMillis

protected void setTimeInMillis(long millis);
Sets this Calendar's current time from the given long value.

Parameters:
date - the new time in UTC milliseconds from the epoch.

O get

public final 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.

O 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.

O 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.

O 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.

O 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.

O 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.

O clear

public final void clear();
Clears the values of all the time fields.

O clear

public final void clear(int field);
Clears the value in the given time field.

Parameters:
field - the time field to be cleared.

O 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.

O complete

protected void complete();
Fills in any unset fields in the time field list.

O 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.

Parameters:
obj - the object to compare with.
Returns:
true if the objects are the same; false otherwise.
Overrides:
equals in class Object

O 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.

O 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.

O 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.

O roll

public abstract void roll(int field,
                          boolean up);
Time Field Rolling function. Rolls (up/down) a single unit of time on the given time field. 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 03/02/96. 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.

O roll

public void roll(int field,
                 int amount);
Time Field Rolling function. Rolls up or down the specified number of units on the given time field. (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.

O setTimeZone

public void setTimeZone(TimeZone value);
Sets the time zone with the given time zone value.

Parameters:
value - the given time zone.

O getTimeZone

public TimeZone getTimeZone();
Gets the time zone.

Returns:
the time zone object associated with this calendar.

O 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:
setLenient

O isLenient

public boolean isLenient();
Tell whether date/time interpretation is to be lenient.

O 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.

O 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.

O 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.

O 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.

O 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.

O 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.

O 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.

O 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.

O clone

public Object clone();
Overrides Cloneable

Overrides:
clone in class Object

O toString

public String toString();
Return a string representation of this calendar.

Returns:
a string representation of this calendar.
Overrides:
toString in class Object

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