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JavaTM 2 Platform Std. Ed. v1.3.1 |
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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 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:
// 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. |
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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)
Overrides Calendar Date Arithmetic function. |
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)
Overrides Calendar Time Field Rolling function. |
void |
roll(int field,
int amount)
Roll a field by a signed amount. |
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.ERApublic 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| 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 compareobj; false otherwisepublic int hashCode()
hashCode in class Calendarjava.util.Calendar
public void add(int field,
int amount)
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)
roll in class Calendarfield - the time field.up - Indicates if rolling up or rolling down the field value.IllegalArgumentException - if an unknown field value is given.
public void roll(int field,
int amount)
roll in class Calendarpublic int getMinimum(int field)
getMinimum in class Calendarjava.util.Calendarfield - the given time field.public int getMaximum(int field)
getMaximum in class Calendarjava.util.Calendarfield - the given time field.public int getGreatestMinimum(int field)
getGreatestMinimum in class Calendarjava.util.Calendarfield - the given time field.public int getLeastMaximum(int field)
getLeastMaximum in class Calendarjava.util.Calendarfield - the given time field.public int getActualMinimum(int field)
getActualMinimum in class Calendarpublic int getActualMaximum(int field)
getActualMaximum in class Calendarprotected void computeFields()
complete method.computeFields in class CalendarCalendar.complete()protected void computeTime()
computeTime in class CalendarIllegalArgumentException - if any fields are invalid.
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JavaTM 2 Platform Std. Ed. v1.3.1 |
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