JavaTM 2 Platform Std. Ed. v1.4.2
java.util
Class GregorianCalendar
java.lang.Object
java.util.Calendar
java.util.GregorianCalendar
- All Implemented Interfaces:
- Cloneable, Serializable
- public class GregorianCalendar
- extends Calendar
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
- Since:
- JDK1.1
- See Also:
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. |
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. |
GregorianCalendar(Locale aLocale)
Constructs a GregorianCalendar based on the current time
in the default time zone with the given locale. |
GregorianCalendar(TimeZone zone)
Constructs a GregorianCalendar based on the current time
in the given time zone with the default locale. |
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()
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 |
BC
public static final int BC
- Value of the
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,...
- See Also:
Calendar.ERA ,
Constant Field Values
AD
public static final int AD
- Value of the
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,...
- See Also:
Calendar.ERA ,
Constant Field Values
GregorianCalendar
public GregorianCalendar()
- Constructs a default GregorianCalendar using the current time
in the default time zone with the default locale.
GregorianCalendar
public GregorianCalendar(TimeZone zone)
- Constructs a GregorianCalendar based on the current time
in the given time zone with the default locale.
- Parameters:
zone - the given time zone.
GregorianCalendar
public GregorianCalendar(Locale aLocale)
- Constructs a GregorianCalendar based on the current time
in the default time zone with the given locale.
- Parameters:
aLocale - the given locale.
GregorianCalendar
public GregorianCalendar(TimeZone zone,
Locale aLocale)
- Constructs a GregorianCalendar based on the current time
in the given time zone with the given locale.
- Parameters:
zone - the given time zone.aLocale - the given locale.
GregorianCalendar
public GregorianCalendar(int year,
int month,
int 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.
GregorianCalendar
public 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.
- 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.
GregorianCalendar
public 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.
- 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.
setGregorianChange
public void setGregorianChange(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.
getGregorianChange
public final Date getGregorianChange()
- 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.
isLeapYear
public boolean isLeapYear(int year)
- 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.
equals
public boolean equals(Object obj)
- Compares this GregorianCalendar to an object reference.
- Overrides:
equals in class Calendar
- Parameters:
obj - the object reference with which to compare
- Returns:
- true if this object is equal to
obj ; false otherwise
hashCode
public int hashCode()
- Override hashCode.
Generates the hash code for the GregorianCalendar object
- Overrides:
hashCode in class Calendar
- Returns:
- a hash code value for this object.
add
public void add(int field,
int amount)
- Adds the specified (signed) amount of time to the given time field,
based on the calendar's rules.
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.
- Specified by:
add in class Calendar
- Parameters:
field - the time field.amount - the amount of date or time to be added to the field.
- Throws:
IllegalArgumentException - if an unknown field is given.
roll
public 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.
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 .
- Specified by:
roll in class Calendar
- Parameters:
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.field - the time field.
- Throws:
IllegalArgumentException - if an unknown field value is given.- See Also:
add(int, int) ,
Calendar.set(int, int)
roll
public void roll(int field,
int amount)
- Add to field a signed amount without changing larger fields.
A negative roll amount means to subtract from field without changing
larger fields.
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).
- Overrides:
roll in class Calendar
- Parameters:
field - the time field.amount - the signed amount to add to field .- Since:
- 1.2
- See Also:
add(int, int) ,
Calendar.set(int, int)
getMinimum
public int getMinimum(int field)
- 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.
- Specified by:
getMinimum in class Calendar
- Parameters:
field - the given time field.
- Returns:
- the minimum value for the given time field.
getMaximum
public int getMaximum(int field)
- 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.
- Specified by:
getMaximum in class Calendar
- Parameters:
field - the given time field.
- Returns:
- the maximum value for the given time field.
getGreatestMinimum
public int getGreatestMinimum(int field)
- 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.
- Specified by:
getGreatestMinimum in class Calendar
- Parameters:
field - the given time field.
- Returns:
- the highest minimum value for the given time field.
getLeastMaximum
public int getLeastMaximum(int field)
- 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.
- Specified by:
getLeastMaximum in class Calendar
- Parameters:
field - the given time field.
- Returns:
- the lowest maximum value for the given time field.
getActualMinimum
public int getActualMinimum(int field)
- 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().
- Overrides:
getActualMinimum in class Calendar
- Parameters:
field - the field to determine the minimum of
- Returns:
- the minimum of the given field for the current date of this Calendar
- Since:
- 1.2
getActualMaximum
public int getActualMaximum(int field)
- 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.
- Overrides:
getActualMaximum in class Calendar
- Parameters:
field - the field to determine the maximum of
- Returns:
- the maximum of the given field for the current date of this Calendar
- Since:
- 1.2
computeFields
protected void computeFields()
- 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.
- Specified by:
computeFields in class Calendar
- See Also:
Calendar.complete()
computeTime
protected void computeTime()
- Overrides Calendar
Converts time field values to UTC as milliseconds.
- Specified by:
computeTime in class Calendar
- Throws:
IllegalArgumentException - if any fields are invalid.
Copyright 2003 Sun Microsystems, Inc. All rights reserved
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