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JavaTM 2 Platform Std. Ed. v1.4.1 |
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java.lang.Object
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+--java.util.Calendar
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+--java.util.GregorianCalendar
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
to 6. 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:
// 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
Calendar,
TimeZone,
Serialized Form| Field Summary | |
static int |
AD
Value of the ERA field indicating
the common era (Anno Domini), also known as CE. |
static int |
BC
Value of the ERA field indicating
the period before the common era (before Christ), also known as BCE. |
| Fields inherited from class java.util.Calendar |
AM, AM_PM, APRIL, areFieldsSet, AUGUST, DATE, DAY_OF_MONTH, DAY_OF_WEEK, DAY_OF_WEEK_IN_MONTH, DAY_OF_YEAR, DECEMBER, DST_OFFSET, ERA, FEBRUARY, FIELD_COUNT, fields, FRIDAY, HOUR, HOUR_OF_DAY, isSet, isTimeSet, JANUARY, JULY, JUNE, MARCH, MAY, MILLISECOND, MINUTE, MONDAY, MONTH, NOVEMBER, OCTOBER, PM, SATURDAY, SECOND, SEPTEMBER, SUNDAY, THURSDAY, time, TUESDAY, UNDECIMBER, WEDNESDAY, WEEK_OF_MONTH, WEEK_OF_YEAR, YEAR, ZONE_OFFSET |
| Constructor Summary | |
GregorianCalendar()
Constructs a default GregorianCalendar using the current time in the default time zone with the default locale. |
|
GregorianCalendar(int year,
int month,
int date)
Constructs a GregorianCalendar with the given date set in the default time zone with the default locale. |
|
GregorianCalendar(int year,
int month,
int date,
int hour,
int minute)
Constructs a GregorianCalendar with the given date and time set for the default time zone with the default locale. |
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GregorianCalendar(int year,
int month,
int date,
int hour,
int minute,
int second)
Constructs a GregorianCalendar with the given date and time set for the default time zone with the default locale. |
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GregorianCalendar(Locale aLocale)
Constructs a GregorianCalendar based on the current time in the default time zone with the given locale. |
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GregorianCalendar(TimeZone zone)
Constructs a GregorianCalendar based on the current time in the given time zone with the default locale. |
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GregorianCalendar(TimeZone zone,
Locale aLocale)
Constructs a GregorianCalendar based on the current time in the given time zone with the given locale. |
|
| Method Summary | |
void |
add(int field,
int amount)
Adds the specified (signed) amount of time to the given time field, based on the calendar's rules. |
protected void |
computeFields()
Overrides Calendar Converts UTC as milliseconds to time field values. |
protected void |
computeTime()
Overrides Calendar Converts time field values to UTC as milliseconds. |
boolean |
equals(Object obj)
Compares this GregorianCalendar to an object reference. |
int |
getActualMaximum(int field)
Return the maximum value that this field could have, given the current date. |
int |
getActualMinimum(int field)
Return the minimum value that this field could have, given the current date. |
int |
getGreatestMinimum(int field)
Returns highest minimum value for the given field if varies. |
Date |
getGregorianChange()
Gets the Gregorian Calendar change date. |
int |
getLeastMaximum(int field)
Returns lowest maximum value for the given field if varies. |
int |
getMaximum(int field)
Returns maximum value for the given field. |
int |
getMinimum(int field)
Returns minimum value for the given field. |
int |
hashCode()
Override hashCode. |
boolean |
isLeapYear(int year)
Determines if the given year is a leap year. |
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)
Add to field a signed amount without changing larger fields. |
void |
setGregorianChange(Date date)
Sets the GregorianCalendar change date. |
| Methods inherited from class java.util.Calendar |
after, before, clear, clear, clone, complete, get, getAvailableLocales, getFirstDayOfWeek, getInstance, getInstance, getInstance, getInstance, getMinimalDaysInFirstWeek, getTime, getTimeInMillis, getTimeZone, internalGet, isLenient, isSet, set, set, set, set, setFirstDayOfWeek, setLenient, setMinimalDaysInFirstWeek, setTime, setTimeInMillis, setTimeZone, toString |
| Methods inherited from class java.lang.Object |
finalize, getClass, notify, notifyAll, wait, wait, wait |
| Field Detail |
public static final int BC
ERA field indicating
the period before the common era (before Christ), also known as BCE.
The sequence of years at the transition from BC to AD is
..., 2 BC, 1 BC, 1 AD, 2 AD,...
Calendar.ERA,
Constant Field Valuespublic static final int AD
ERA field indicating
the common era (Anno Domini), also known as CE.
The sequence of years at the transition from BC to AD is
..., 2 BC, 1 BC, 1 AD, 2 AD,...
Calendar.ERA,
Constant Field Values| Constructor Detail |
public GregorianCalendar()
public GregorianCalendar(TimeZone zone)
zone - the given time zone.public GregorianCalendar(Locale aLocale)
aLocale - the given locale.
public GregorianCalendar(TimeZone zone,
Locale aLocale)
zone - the given time zone.aLocale - the given locale.
public GregorianCalendar(int year,
int month,
int date)
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.
public GregorianCalendar(int year,
int month,
int date,
int hour,
int minute)
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.
public GregorianCalendar(int year,
int month,
int date,
int hour,
int minute,
int second)
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.| Method Detail |
public void setGregorianChange(Date date)
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).
date - the given Gregorian cutover date.public final Date getGregorianChange()
public boolean isLeapYear(int year)
year - the given year.
public boolean equals(Object obj)
equals in class Calendarobj - the object reference with which to compare
obj; false otherwisepublic int hashCode()
hashCode in class Calendar
public void add(int field,
int amount)
Add rule 1. The value of field
after the call minus the value of field before the
call is amount, modulo any overflow that has occurred in
field. 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 is changed, then its value is adjusted to be as close
as possible to its expected value. A smaller field represents a
smaller unit of time. HOUR is a smaller field than
DAY_OF_MONTH. No adjustment is made to smaller fields
that are not expected to be invariant. The calendar system
determines what fields are expected to be invariant.
add in class Calendarfield - the time field.amount - the amount of date or time to be added to the field.
IllegalArgumentException - if an unknown field is given.
public void roll(int field,
boolean up)
Example: Consider a GregorianCalendar
originally set to December 31, 1999. Calling roll(Calendar.MONTH, true)
sets the calendar to January 31, 1999. The Year field is unchanged
because it is a larger field than MONTH.
roll in class Calendarup - indicates if the value of the specified time field is to be
rolled up or rolled down. Use true if rolling up, false otherwise.field - the time field.
IllegalArgumentException - if an unknown field value is given.add(int, int),
Calendar.set(int, int)
public void roll(int field,
int amount)
Example: Consider a GregorianCalendar
originally set to August 31, 1999. Calling roll(Calendar.MONTH,
8) sets the calendar to April 30, 1999. Using a
GregorianCalendar, the DAY_OF_MONTH field cannot
be 31 in the month April. DAY_OF_MONTH is set to the closest possible
value, 30. The YEAR field maintains the value of 1999 because it
is a larger field than MONTH.
Example: Consider a GregorianCalendar
originally set to Sunday June 6, 1999. Calling
roll(Calendar.WEEK_OF_MONTH, -1) sets the calendar to
Tuesday June 1, 1999, whereas calling
add(Calendar.WEEK_OF_MONTH, -1) sets the calendar to
Sunday May 30, 1999. This is because the roll rule imposes an
additional constraint: The MONTH must not change when the
WEEK_OF_MONTH is rolled. Taken together with add rule 1,
the resultant date must be between Tuesday June 1 and Saturday June
5. According to add rule 2, the DAY_OF_WEEK, an invariant
when changing the WEEK_OF_MONTH, is set to Tuesday, the
closest possible value to Sunday (where Sunday is the first day of the
week).
roll in class Calendarfield - the time field.amount - the signed amount to add to field.add(int, int),
Calendar.set(int, int)public int getMinimum(int field)
getMinimum in class Calendarfield - the given time field.
public int getMaximum(int field)
getMaximum in class Calendarfield - the given time field.
public int getGreatestMinimum(int field)
getGreatestMinimum in class Calendarfield - the given time field.
public int getLeastMaximum(int field)
getLeastMaximum in class Calendarfield - the given time field.
public int getActualMinimum(int field)
getActualMinimum in class Calendarfield - the field to determine the minimum of
public int getActualMaximum(int field)
getActualMaximum in class Calendarfield - the field to determine the maximum of
protected void computeFields()
complete method.
computeFields in class CalendarCalendar.complete()protected void computeTime()
computeTime in class CalendarIllegalArgumentException - if any fields are invalid.
|
JavaTM 2 Platform Std. Ed. v1.4.1 |
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| PREV CLASS NEXT CLASS | FRAMES NO FRAMES | ||||||||||
| SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD | ||||||||||
Copyright 2002 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.