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

Author:

David Goldsmith, Mark Davis, Chen-Lieh Huang, Alan Liu

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.
private static int	EPOCH_JULIAN_DAY
private static int	EPOCH_YEAR
private long	gregorianCutover The point at which the Gregorian calendar rules are used, measured in milliseconds from the standard epoch.
private int	gregorianCutoverYear The year of the gregorianCutover, with 0 representing 1 BC, -1 representing 2 BC, etc.
private static int	JAN_1_1_JULIAN_DAY
private static int[]	LEAP_MONTH_LENGTH
private static int[]	LEAP_NUM_DAYS
private static int[]	LEAST_MAX_VALUES
private static int[]	MAX_VALUES
private static int[]	MIN_VALUES
private static int[]	MONTH_LENGTH
private long	normalizedGregorianCutover Midnight, local time (using this Calendar's TimeZone) at or before the gregorianCutover.
private static int[]	NUM_DAYS
private static long	ONE_DAY
private static int	ONE_HOUR
private static int	ONE_MINUTE
private static int	ONE_SECOND
private static long	ONE_WEEK
(package private) static long	serialVersionUID

Fields inherited from class java.util.Calendar

AM, AM_PM, APRIL, areAllFieldsSet, areFieldsSet, AUGUST, currentSerialVersion, 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, INTERNALLY_SET, isSet, isTimeSet, JANUARY, JULY, JUNE, MARCH, MAY, MILLISECOND, MINIMUM_USER_STAMP, MINUTE, MONDAY, MONTH, NOVEMBER, OCTOBER, PM, SATURDAY, SECOND, SEPTEMBER, stamp, SUNDAY, THURSDAY, time, TUESDAY, UNDECIMBER, UNSET, 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.
private static int	aggregateStamp(int stamp_a, int stamp_b) Return the pseudo-time-stamp for two fields, given their individual pseudo-time-stamps.
private boolean	boundsCheck(int value, int field) Validates the value of the given time field.
protected void	computeFields() Converts UTC as milliseconds to time field values.
private void	computeFieldsImpl() This computeFieldsImpl implements the conversion from UTC (a millisecond offset from 1970-01-01T00:00:00.000Z) to calendar field values.
private long	computeJulianDay(boolean isGregorian, int year, int[] fieldMaskParam) Compute the Julian day number under either the Gregorian or the Julian calendar, using the given year and the remaining fields.
protected void	computeTime() Overrides Calendar Converts time field values to UTC as milliseconds.
boolean	equals(Object obj) Compares this GregorianCalendar to an object reference.
private static int	floorDivide(int numerator, int denominator) Divide two integers, returning the floor of the quotient.
private static int	floorDivide(int numerator, int denominator, int[] remainder) Divide two integers, returning the floor of the quotient, and the modulus remainder.
private static int	floorDivide(long numerator, int denominator, int[] remainder) Divide two integers, returning the floor of the quotient, and the modulus remainder.
private static long	floorDivide(long numerator, long denominator) Divide two long integers, returning the floor of the quotient.
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.
private long	getEpochDay() Return the day number with respect to the epoch.
int	getGreatestMinimum(int field) Returns highest minimum value for the given field if varies.
Date	getGregorianChange() Gets the Gregorian Calendar change date.
(package private) int	getISOYear() Return the year that corresponds to the WEEK_OF_YEAR field.
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.
(package private) boolean	inDaylightTime() Return true if the current time for this Calendar is in Daylignt Savings Time.
private int	internalGetEra() Return the ERA.
boolean	isLeapYear(int year) Determines if the given year is a leap year.
private static int	julianDayToDayOfWeek(long julian)
private static long	julianDayToMillis(long julian) Converts Julian day to time as milliseconds.
private static long	millisToJulianDay(long millis) Converts time as milliseconds to Julian day.
private int	monthLength(int month)
private int	monthLength(int month, int year)
private void	pinDayOfMonth() After adjustments such as add(MONTH), add(YEAR), we don't want the month to jump around.
private int	prevMonthLength(int month) Returns the length of the previous month.
private void	readObject(ObjectInputStream stream) Updates internal state.
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.
private void	timeToFields(long theTime, boolean quick) Convert the time as milliseconds to the date fields.
private boolean	validateFields() Validates the values of the set time fields.
private int	weekNumber(int dayOfPeriod, int dayOfWeek) Return the week number of a day, within a period.
private int	yearLength()
private int	yearLength(int year)

Methods inherited from class java.util.Calendar

after, before, clear, clear, clone, complete, get, getAvailableLocales, getFirstDayOfWeek, getInstance, getInstance, getInstance, getInstance, getMinimalDaysInFirstWeek, getTime, getTimeInMillis, getTimeZone, internalClear, internalGet, internalSet, 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

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

JAN_1_1_JULIAN_DAY

private static final int JAN_1_1_JULIAN_DAY

See Also:

Constant Field Values

EPOCH_JULIAN_DAY

private static final int EPOCH_JULIAN_DAY

See Also:

Constant Field Values

EPOCH_YEAR

private static final int EPOCH_YEAR

See Also:

Constant Field Values

NUM_DAYS

private static final int[] NUM_DAYS

LEAP_NUM_DAYS

private static final int[] LEAP_NUM_DAYS

MONTH_LENGTH

private static final int[] MONTH_LENGTH

LEAP_MONTH_LENGTH

private static final int[] LEAP_MONTH_LENGTH

ONE_SECOND

private static final int ONE_SECOND

See Also:

Constant Field Values

ONE_MINUTE

private static final int ONE_MINUTE

See Also:

Constant Field Values

ONE_HOUR

private static final int ONE_HOUR

See Also:

Constant Field Values

ONE_DAY

private static final long ONE_DAY

See Also:

Constant Field Values

ONE_WEEK

private static final long ONE_WEEK

See Also:

Constant Field Values

MIN_VALUES

private static final int[] MIN_VALUES

LEAST_MAX_VALUES

private static final int[] LEAST_MAX_VALUES

MAX_VALUES

private static final int[] MAX_VALUES

gregorianCutover

private long gregorianCutover

The point at which the Gregorian calendar rules are used, measured in milliseconds from the standard epoch. Default is October 15, 1582 (Gregorian) 00:00:00 UTC or -12219292800000L. For this value, October 4, 1582 (Julian) is followed by October 15, 1582 (Gregorian). This corresponds to Julian day number 2299161.

normalizedGregorianCutover

private transient long normalizedGregorianCutover

Midnight, local time (using this Calendar's TimeZone) at or before the gregorianCutover. This is a pure date value with no time of day or timezone component.

gregorianCutoverYear

private transient int gregorianCutoverYear

The year of the gregorianCutover, with 0 representing 1 BC, -1 representing 2 BC, etc.

serialVersionUID

static final long serialVersionUID

See Also:

Constant Field Values

Constructor Detail

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.

Method Detail

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

inDaylightTime

boolean inDaylightTime()

Return true if the current time for this Calendar is in Daylignt Savings Time. Note -- MAKE THIS PUBLIC AT THE NEXT API CHANGE. POSSIBLY DEPRECATE AND REMOVE TimeZone.inDaylightTime().

getISOYear

int getISOYear()

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:

Calendar.WEEK_OF_YEAR

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()

computeFieldsImpl

private void computeFieldsImpl()

This computeFieldsImpl implements the conversion from UTC (a millisecond offset from 1970-01-01T00:00:00.000Z) to calendar field values.

timeToFields

private final void timeToFields(long theTime,
                                boolean quick)

Convert the time as milliseconds to the date fields. Millis must be given as local wall millis to get the correct local day. For example, if it is 11:30 pm Standard, and DST is in effect, the correct DST millis must be passed in to get the right date.

Fields that are completed by this method: ERA, YEAR, MONTH, DATE, DAY_OF_WEEK, DAY_OF_YEAR, WEEK_OF_YEAR, WEEK_OF_MONTH, DAY_OF_WEEK_IN_MONTH.

Parameters:

theTime - the wall-clock time in milliseconds (either Standard or DST), whichever is in effect

quick - if true, only compute the ERA, YEAR, MONTH, DATE, DAY_OF_WEEK, and DAY_OF_YEAR.

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.

computeJulianDay

private final long computeJulianDay(boolean isGregorian,
                                    int year,
                                    int[] fieldMaskParam)

Compute the Julian day number under either the Gregorian or the Julian calendar, using the given year and the remaining fields.

Parameters:

isGregorian - if true, use the Gregorian calendar

year - the adjusted year number, with 0 indicating the year 1 BC, -1 indicating 2 BC, etc.

fieldMaskParam - fieldMaskParam[0] is a bit mask to specify which fields have been used to determine the date. The value is updated upon return.

Returns:

the Julian day number

millisToJulianDay

private static final long millisToJulianDay(long millis)

Converts time as milliseconds to Julian day.

Parameters:

millis - the given milliseconds.

Returns:

the Julian day number.

julianDayToMillis

private static final long julianDayToMillis(long julian)

Converts Julian day to time as milliseconds.

Parameters:

julian - the given Julian day number.

Returns:

time as milliseconds.

julianDayToDayOfWeek

private static final int julianDayToDayOfWeek(long julian)

floorDivide

private static final long floorDivide(long numerator,
                                      long denominator)

Divide two long integers, returning the floor of the quotient.

Unlike the built-in division, this is mathematically well-behaved. E.g., -1/4 => 0 but floorDivide(-1,4) => -1.

Parameters:

numerator - the numerator

denominator - a divisor which must be > 0

Returns:

the floor of the quotient.

floorDivide

private static final int floorDivide(int numerator,
                                     int denominator)

Divide two integers, returning the floor of the quotient.

Unlike the built-in division, this is mathematically well-behaved. E.g., -1/4 => 0 but floorDivide(-1,4) => -1.

Parameters:

numerator - the numerator

denominator - a divisor which must be > 0

Returns:

the floor of the quotient.

floorDivide

private static final int floorDivide(int numerator,
                                     int denominator,
                                     int[] remainder)

Divide two integers, returning the floor of the quotient, and the modulus remainder.

Unlike the built-in division, this is mathematically well-behaved. E.g., -1/4 => 0 and -1%4 => -1, but floorDivide(-1,4) => -1 with remainder[0] => 3.

Parameters:

numerator - the numerator

denominator - a divisor which must be > 0

remainder - an array of at least one element in which the value numerator mod denominator is returned. Unlike numerator % denominator, this will always be non-negative.

Returns:

the floor of the quotient.

floorDivide

private static final int floorDivide(long numerator,
                                     int denominator,
                                     int[] remainder)

Divide two integers, returning the floor of the quotient, and the modulus remainder.

Unlike the built-in division, this is mathematically well-behaved. E.g., -1/4 => 0 and -1%4 => -1, but floorDivide(-1,4) => -1 with remainder[0] => 3.

Parameters:

numerator - the numerator

denominator - a divisor which must be > 0

remainder - an array of at least one element in which the value numerator mod denominator is returned. Unlike numerator % denominator, this will always be non-negative.

Returns:

the floor of the quotient.

aggregateStamp

private static final int aggregateStamp(int stamp_a,
                                        int stamp_b)

Return the pseudo-time-stamp for two fields, given their individual pseudo-time-stamps. If either of the fields is unset, then the aggregate is unset. Otherwise, the aggregate is the later of the two stamps.

weekNumber

private final int weekNumber(int dayOfPeriod,
                             int dayOfWeek)

Return the week number of a day, within a period. This may be the week number in a year, or the week number in a month. Usually this will be a value >= 1, but if some initial days of the period are excluded from week 1, because minimalDaysInFirstWeek is > 1, then the week number will be zero for those initial days. Requires the day of week for the given date in order to determine the day of week of the first day of the period.

Parameters:

dayOfPeriod - Day-of-year or day-of-month. Should be 1 for first day of period.

Returns:

Week number, one-based, or zero if the day falls in part of the month before the first week, when there are days before the first week because the minimum days in the first week is more than one.

monthLength

private final int monthLength(int month,
                              int year)

monthLength

private final int monthLength(int month)

prevMonthLength

private final int prevMonthLength(int month)

Returns the length of the previous month. For January, returns the arbitrary value 31, which will not be used: This value is passed to SimpleTimeZone.getOffset(), and if the month is -1 (the month before January), the day value will be ignored.

yearLength

private final int yearLength(int year)

yearLength

private final int yearLength()

pinDayOfMonth

private final void pinDayOfMonth()

After adjustments such as add(MONTH), add(YEAR), we don't want the month to jump around. E.g., we don't want Jan 31 + 1 month to go to Mar 3, we want it to go to Feb 28. Adjustments which might run into this problem call this method to retain the proper month.

validateFields

private boolean validateFields()

Validates the values of the set time fields.

boundsCheck

private final boolean boundsCheck(int value,
                                  int field)

Validates the value of the given time field.

getEpochDay

private final long getEpochDay()

Return the day number with respect to the epoch. January 1, 1970 (Gregorian) is day zero.

internalGetEra

private final int internalGetEra()

Return the ERA. We need a special method for this because the default ERA is AD, but a zero (unset) ERA is BC.

readObject

private void readObject(ObjectInputStream stream)
                 throws IOException,
                        ClassNotFoundException

Updates internal state.

Throws:

IOException

ClassNotFoundException