java::util::GregorianCalendar Class Reference

Inheritance diagram for java::util::GregorianCalendar:

Inheritance graph
java::util::Calendarjava::lang::Object
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Collaboration diagram for java::util::GregorianCalendar:

Collaboration graph
java::util::Calendarjava::lang::Object
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List of all members.


Detailed Description

GregorianCalendar is a concrete subclass of Calendar and provides the standard calendar used by most of the world.

The standard (Gregorian) calendar has 2 eras, BC and AD.

This implementation handles a single discontinuity, which corresponds by default to the date the Gregorian calendar was instituted (October 15, 1582 in some countries, later in others). The cutover date may be changed by the caller by calling setGregorianChange().

Historically, in those countries which adopted the Gregorian calendar first, October 4, 1582 was thus followed by October 15, 1582. This calendar models this correctly. Before the Gregorian cutover, GregorianCalendar implements the Julian calendar. The only difference between the Gregorian and the Julian calendar is the leap year rule. The Julian calendar specifies leap years every four years, whereas the Gregorian calendar omits century years which are not divisible by 400.

GregorianCalendar implements proleptic Gregorian and Julian calendars. That is, dates are computed by extrapolating the current rules indefinitely far backward and forward in time. As a result, GregorianCalendar may be used for all years to generate meaningful and consistent results. However, dates obtained using GregorianCalendar are historically accurate only from March 1, 4 AD onward, when modern Julian calendar rules were adopted. Before this date, leap year rules were applied irregularly, and before 45 BC the Julian calendar did not even exist.

Prior to the institution of the Gregorian calendar, New Year's Day was March 25. To avoid confusion, this calendar always uses January 1. A manual adjustment may be made if desired for dates that are prior to the Gregorian changeover and which fall between January 1 and March 24.

Values calculated for the WEEK_OF_YEAR field range from 1 to 53. Week 1 for a year is the earliest seven day period starting on getFirstDayOfWeek() that contains at least getMinimalDaysInFirstWeek() days from that year. It thus depends on the values of getMinimalDaysInFirstWeek(), getFirstDayOfWeek(), and the day of the week of January 1. Weeks between week 1 of one year and week 1 of the following year are numbered sequentially from 2 to 52 or 53 (as needed).

For example, January 1, 1998 was a Thursday. If getFirstDayOfWeek() is MONDAY and getMinimalDaysInFirstWeek() is 4 (these are the values reflecting ISO 8601 and many national standards), then week 1 of 1998 starts on December 29, 1997, and ends on January 4, 1998. If, however, getFirstDayOfWeek() is SUNDAY, then week 1 of 1998 starts on January 4, 1998, and ends on January 10, 1998; the first three days of 1998 then are part of week 53 of 1997.

Values calculated for the WEEK_OF_MONTH field range from 0 or 1 to 4 or 5. Week 1 of a month (the days with WEEK_OF_MONTH = 1) is the earliest set of at least getMinimalDaysInFirstWeek() contiguous days in that month, ending on the day before getFirstDayOfWeek(). Unlike week 1 of a year, week 1 of a month may be shorter than 7 days, need not start on getFirstDayOfWeek(), and will not include days of the previous month. Days of a month before week 1 have a WEEK_OF_MONTH of 0.

For example, if getFirstDayOfWeek() is SUNDAY and getMinimalDaysInFirstWeek() is 4, then the first week of January 1998 is Sunday, January 4 through Saturday, January 10. These days have a WEEK_OF_MONTH of 1. Thursday, January 1 through Saturday, January 3 have a WEEK_OF_MONTH of 0. If getMinimalDaysInFirstWeek() is changed to 3, then January 1 through January 3 have a WEEK_OF_MONTH of 1.

Example: <blockquote>

 // get the supported ids for GMT-08:00 (Pacific Standard Time)
 String[] ids = TimeZone.getAvailableIDs(-8 * 60 * 60 * 1000);
 // if no ids were returned, something is wrong. get out.
 if (ids.length == 0)
     System.exit(0);

  // begin output
 System.out.println("Current Time");

 // create a Pacific Standard Time time zone
 SimpleTimeZone pdt = new SimpleTimeZone(-8 * 60 * 60 * 1000, ids[0]);

 // set up rules for daylight savings time
 pdt.setStartRule(Calendar.APRIL, 1, Calendar.SUNDAY, 2 * 60 * 60 * 1000);
 pdt.setEndRule(Calendar.OCTOBER, -1, Calendar.SUNDAY, 2 * 60 * 60 * 1000);

 // create a GregorianCalendar with the Pacific Daylight time zone
 // and the current date and time
 Calendar calendar = new GregorianCalendar(pdt);
 Date trialTime = new Date();
 calendar.setTime(trialTime);

 // print out a bunch of interesting things
 System.out.println("ERA: " + calendar.get(Calendar.ERA));
 System.out.println("YEAR: " + calendar.get(Calendar.YEAR));
 System.out.println("MONTH: " + calendar.get(Calendar.MONTH));
 System.out.println("WEEK_OF_YEAR: " + calendar.get(Calendar.WEEK_OF_YEAR));
 System.out.println("WEEK_OF_MONTH: " + calendar.get(Calendar.WEEK_OF_MONTH));
 System.out.println("DATE: " + calendar.get(Calendar.DATE));
 System.out.println("DAY_OF_MONTH: " + calendar.get(Calendar.DAY_OF_MONTH));
 System.out.println("DAY_OF_YEAR: " + calendar.get(Calendar.DAY_OF_YEAR));
 System.out.println("DAY_OF_WEEK: " + calendar.get(Calendar.DAY_OF_WEEK));
 System.out.println("DAY_OF_WEEK_IN_MONTH: "
                    + calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH));
 System.out.println("AM_PM: " + calendar.get(Calendar.AM_PM));
 System.out.println("HOUR: " + calendar.get(Calendar.HOUR));
 System.out.println("HOUR_OF_DAY: " + calendar.get(Calendar.HOUR_OF_DAY));
 System.out.println("MINUTE: " + calendar.get(Calendar.MINUTE));
 System.out.println("SECOND: " + calendar.get(Calendar.SECOND));
 System.out.println("MILLISECOND: " + calendar.get(Calendar.MILLISECOND));
 System.out.println("ZONE_OFFSET: "
                    + (calendar.get(Calendar.ZONE_OFFSET)/(60*60*1000)));
 System.out.println("DST_OFFSET: "
                    + (calendar.get(Calendar.DST_OFFSET)/(60*60*1000)));
 System.out.println("Current Time, with hour reset to 3");
 calendar.clear(Calendar.HOUR_OF_DAY); // so doesn't override
 calendar.set(Calendar.HOUR, 3);
 System.out.println("ERA: " + calendar.get(Calendar.ERA));
 System.out.println("YEAR: " + calendar.get(Calendar.YEAR));
 System.out.println("MONTH: " + calendar.get(Calendar.MONTH));
 System.out.println("WEEK_OF_YEAR: " + calendar.get(Calendar.WEEK_OF_YEAR));
 System.out.println("WEEK_OF_MONTH: " + calendar.get(Calendar.WEEK_OF_MONTH));
 System.out.println("DATE: " + calendar.get(Calendar.DATE));
 System.out.println("DAY_OF_MONTH: " + calendar.get(Calendar.DAY_OF_MONTH));
 System.out.println("DAY_OF_YEAR: " + calendar.get(Calendar.DAY_OF_YEAR));
 System.out.println("DAY_OF_WEEK: " + calendar.get(Calendar.DAY_OF_WEEK));
 System.out.println("DAY_OF_WEEK_IN_MONTH: "
                    + calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH));
 System.out.println("AM_PM: " + calendar.get(Calendar.AM_PM));
 System.out.println("HOUR: " + calendar.get(Calendar.HOUR));
 System.out.println("HOUR_OF_DAY: " + calendar.get(Calendar.HOUR_OF_DAY));
 System.out.println("MINUTE: " + calendar.get(Calendar.MINUTE));
 System.out.println("SECOND: " + calendar.get(Calendar.SECOND));
 System.out.println("MILLISECOND: " + calendar.get(Calendar.MILLISECOND));
 System.out.println("ZONE_OFFSET: "
        + (calendar.get(Calendar.ZONE_OFFSET)/(60*60*1000))); // in hours
 System.out.println("DST_OFFSET: "
        + (calendar.get(Calendar.DST_OFFSET)/(60*60*1000))); // in hours
 
</blockquote>

See also:
Calendar

TimeZone

Version:
1.53
Author:
David Goldsmith, Mark Davis, Chen-Lieh Huang, Alan Liu
Since:
DK1.1

Public Types

enum  { BC = 0, AD }

Public Member Functions

 GregorianCalendar ()
 Constructs a default GregorianCalendar using the current time in the default time zone.
 GregorianCalendar (const TimeZone &zone)
 Constructs a GregorianCalendar based on the current time in the given time zone.
 GregorianCalendar (jint year, jint month, jint date)
 Constructs a GregorianCalendar with the given date set in the default time zone with the default locale.
 GregorianCalendar (jint year, jint month, jint date, jint hour, jint minute)
 Constructs a GregorianCalendar with the given date and time set for the default time zone with the default locale.
 GregorianCalendar (jint year, jint month, jint date, jint hour, jint minute, jint second)
 Constructs a GregorianCalendar with the given date and time set for the default time zone with the default locale.
void setGregorianChange (const Date &date)
 Sets the GregorianCalendar change date.
const Date getGregorianChange () const
 Gets the Gregorian Calendar change date.
virtual jboolean isLeapYear (jint year) const
 Determines if the given year is a leap year.
virtual jboolean equals (const Object &obj) const
 Compares this GregorianCalendar to an object reference.
virtual jint hashCode () const
 Override hashCode.
virtual void add (jint field, jint amount)
 Overrides Calendar Date Arithmetic function.
virtual void roll (jint field, jboolean up)
 Overrides Calendar Time Field Rolling function.
virtual void roll (jint field, jint amount)
 Roll a field by a signed amount.
virtual jint getMinimum (jint field) const
 Returns minimum value for the given field.
virtual jint getMaximum (jint field) const
 Returns maximum value for the given field.
virtual jint getGreatestMinimum (jint field) const
 Returns highest minimum value for the given field if varies.
virtual jint getLeastMaximum (jint field) const
 Returns lowest maximum value for the given field if varies.
virtual jint getActualMinimum (jint field) const
 Return the minimum value that this field could have, given the current date.
virtual jint getActualMaximum (jint field) const
 Return the maximum value that this field could have, given the current date.
virtual jboolean inDaylightTime () const
 Return true if the current time for this Calendar is in Daylignt Savings Time.
virtual jint getISOYear () const
 Return the year that corresponds to the WEEK_OF_YEAR field.

Protected Member Functions

virtual void computeFields ()
 Overrides Calendar Converts UTC as milliseconds to time field values.
virtual void computeTime ()
 Overrides Calendar Converts time field values to UTC as milliseconds.

Member Enumeration Documentation

anonymous enum

Enumerator:
BC  Useful constant for GregorianCalendar.
AD 


Constructor & Destructor Documentation

java::util::GregorianCalendar::GregorianCalendar (  ) 

Constructs a default GregorianCalendar using the current time in the default time zone.

java::util::GregorianCalendar::GregorianCalendar ( const TimeZone zone  ) 

Constructs a GregorianCalendar based on the current time in the given time zone.

Parameters:
zone the given time zone.

java::util::GregorianCalendar::GregorianCalendar ( jint  year,
jint  month,
jint  date 
)

Constructs a GregorianCalendar with the given date set in the default time zone with the default locale.

Parameters:
year the value used to set the YEAR time field in the calendar.
month the value used to set the MONTH time field in the calendar. Month value is 0-based. e.g., 0 for January.
date the value used to set the DATE time field in the calendar.

java::util::GregorianCalendar::GregorianCalendar ( jint  year,
jint  month,
jint  date,
jint  hour,
jint  minute 
)

Constructs a GregorianCalendar with the given date and time set for the default time zone with the default locale.

Parameters:
year the value used to set the YEAR time field in the calendar.
month the value used to set the MONTH time field in the calendar. Month value is 0-based. e.g., 0 for January.
date the value used to set the DATE time field in the calendar.
hour the value used to set the HOUR_OF_DAY time field in the calendar.
minute the value used to set the MINUTE time field in the calendar.

java::util::GregorianCalendar::GregorianCalendar ( jint  year,
jint  month,
jint  date,
jint  hour,
jint  minute,
jint  second 
)

Constructs a GregorianCalendar with the given date and time set for the default time zone with the default locale.

Parameters:
year the value used to set the YEAR time field in the calendar.
month the value used to set the MONTH time field in the calendar. Month value is 0-based. e.g., 0 for January.
date the value used to set the DATE time field in the calendar.
hour the value used to set the HOUR_OF_DAY time field in the calendar.
minute the value used to set the MINUTE time field in the calendar.
second the value used to set the SECOND time field in the calendar.


Member Function Documentation

void java::util::GregorianCalendar::setGregorianChange ( const Date date  ) 

Sets the GregorianCalendar change date.

This is the point when the switch from Julian dates to Gregorian dates occurred. Default is October 15, 1582. Previous to this, dates will be in the Julian calendar.

To obtain a pure Julian calendar, set the change date to Date(Long.MAX_VALUE). To obtain a pure Gregorian calendar, set the change date to Date(Long.MIN_VALUE).

Parameters:
date the given Gregorian cutover date.

const Date java::util::GregorianCalendar::getGregorianChange (  )  const

Gets the Gregorian Calendar change date.

This is the point when the switch from Julian dates to Gregorian dates occurred. Default is October 15, 1582. Previous to this, dates will be in the Julian calendar.

Returns:
the Gregorian cutover date for this calendar.

virtual jboolean java::util::GregorianCalendar::isLeapYear ( jint  year  )  const [virtual]

Determines if the given year is a leap year.

Returns true if the given year is a leap year.

Parameters:
year the given year.
Returns:
true if the given year is a leap year; false otherwise.

virtual jboolean java::util::GregorianCalendar::equals ( const Object obj  )  const [virtual]

Compares this GregorianCalendar to an object reference.

Parameters:
obj the object reference with which to compare
Returns:
true if this object is equal to obj; false otherwise

Reimplemented from java::util::Calendar.

virtual jint java::util::GregorianCalendar::hashCode (  )  const [virtual]

Override hashCode.

Generates the hash code for the GregorianCalendar object

Reimplemented from java::util::Calendar.

virtual void java::util::GregorianCalendar::add ( jint  field,
jint  amount 
) [virtual]

Overrides Calendar Date Arithmetic function.

Adds the specified (signed) amount of time to the given time field, based on the calendar's rules.

Parameters:
field the time field.
amount the amount of date or time to be added to the field.
Exceptions:
IllegalArgumentException if an unknown field is given.

Implements java::util::Calendar.

virtual void java::util::GregorianCalendar::roll ( jint  field,
jboolean  up 
) [virtual]

Overrides Calendar Time Field Rolling function.

Rolls (up/down) a single unit of time on the given time field.

Parameters:
field the time field.
up Indicates if rolling up or rolling down the field value.
Exceptions:
IllegalArgumentException if an unknown field value is given.

Implements java::util::Calendar.

virtual void java::util::GregorianCalendar::roll ( jint  field,
jint  amount 
) [virtual]

Roll a field by a signed amount.

Since:
1.2

Reimplemented from java::util::Calendar.

virtual jint java::util::GregorianCalendar::getMinimum ( jint  field  )  const [virtual]

Returns minimum value for the given field.

e.g. for Gregorian DAY_OF_MONTH, 1 Please see Calendar.getMinimum for descriptions on parameters and the return value.

Implements java::util::Calendar.

virtual jint java::util::GregorianCalendar::getMaximum ( jint  field  )  const [virtual]

Returns maximum value for the given field.

e.g. for Gregorian DAY_OF_MONTH, 31 Please see Calendar.getMaximum for descriptions on parameters and the return value.

Implements java::util::Calendar.

virtual jint java::util::GregorianCalendar::getGreatestMinimum ( jint  field  )  const [virtual]

Returns highest minimum value for the given field if varies.

Otherwise same as getMinimum(). For Gregorian, no difference. Please see Calendar.getGreatestMinimum for descriptions on parameters and the return value.

Implements java::util::Calendar.

virtual jint java::util::GregorianCalendar::getLeastMaximum ( jint  field  )  const [virtual]

Returns lowest maximum value for the given field if varies.

Otherwise same as getMaximum(). For Gregorian DAY_OF_MONTH, 28 Please see Calendar.getLeastMaximum for descriptions on parameters and the return value.

Implements java::util::Calendar.

virtual jint java::util::GregorianCalendar::getActualMinimum ( jint  field  )  const [virtual]

Return the minimum value that this field could have, given the current date.

For the Gregorian calendar, this is the same as getMinimum() and getGreatestMinimum().

Since:
1.2

Reimplemented from java::util::Calendar.

virtual jint java::util::GregorianCalendar::getActualMaximum ( jint  field  )  const [virtual]

Return the maximum value that this field could have, given the current date.

For example, with the date "Feb 3, 1997" and the DAY_OF_MONTH field, the actual maximum would be 28; for "Feb 3, 1996" it s 29. Similarly for a Hebrew calendar, for some years the actual maximum for MONTH is 12, and for others 13.

Since:
1.2

Reimplemented from java::util::Calendar.

virtual jboolean java::util::GregorianCalendar::inDaylightTime (  )  const [virtual]

Return true if the current time for this Calendar is in Daylignt Savings Time.

Implements java::util::Calendar.

virtual jint java::util::GregorianCalendar::getISOYear (  )  const [virtual]

Return the year that corresponds to the WEEK_OF_YEAR field.

This may be one year before or after the calendar year stored in the YEAR field. For example, January 1, 1999 is considered Friday of week 53 of 1998 (if minimal days in first week is 2 or less, and the first day of the week is Sunday). Given these same settings, the ISO year of January 1, 1999 is 1998.

Warning: This method will complete all fields.

Returns:
the year corresponding to the WEEK_OF_YEAR field, which may be one year before or after the YEAR field.
See also:
WEEK_OF_YEAR

virtual void java::util::GregorianCalendar::computeFields (  )  [protected, virtual]

Overrides Calendar Converts UTC as milliseconds to time field values.

The time is not recomputed first; to recompute the time, then the fields, call the complete method.

See also:
Calendar::complete

Implements java::util::Calendar.

virtual void java::util::GregorianCalendar::computeTime (  )  [protected, virtual]

Overrides Calendar Converts time field values to UTC as milliseconds.

Exceptions:
IllegalArgumentException if any fields are invalid.

Implements java::util::Calendar.


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