ChineseCalendar
is a concrete subclass of
Calendar
that implements a traditional Chinese calendar. The traditional Chinese
calendar is a lunisolar calendar: Each month starts on a new moon, and
the months are numbered according to solar events, specifically, to
guarantee that month 11 always contains the winter solstice. In order
to accomplish this, leap months are inserted in certain years. Leap
months are numbered the same as the month they follow. The decision of
which month is a leap month depends on the relative movements of the sun
and moon.
This class defines one addition field beyond those defined by
Calendar
: The
IS_LEAP_MONTH
field takes the
value of 0 for normal months, or 1 for leap months.
All astronomical computations are performed with respect to a time
zone of GMT+8:00 and a longitude of 120 degrees east. Although some
calendars implement a historically more accurate convention of using
Beijing's local longitude (116 degrees 25 minutes east) and time zone
(GMT+7:45:40) for dates before 1929, we do not implement this here.
Years are counted in two different ways in the Chinese calendar. The
first method is by sequential numbering from the 61st year of the reign
of Huang Di, 2637 BCE, which is designated year 1 on the Chinese
calendar. The second method uses 60-year cycles from the same starting
point, which is designated year 1 of cycle 1. In this class, the
EXTENDED_YEAR
field contains the sequential year count.
The
ERA
field contains the cycle number, and the
YEAR
field contains the year of the cycle, a value between
1 and 60.
There is some variation in what is considered the starting point of
the calendar, with some sources starting in the first year of the reign
of Huang Di, rather than the 61st. This gives continuous year numbers
60 years greater and cycle numbers one greater than what this class
implements.
Because
ChineseCalendar
defines an additional field and
redefines the way the
ERA
field is used, it requires a new
format class,
ChineseDateFormat
. As always, use the
methods
DateFormat.getXxxInstance(Calendar cal,...)
to
obtain a formatter for this calendar.
References:
This class should not be subclassed.
ChineseCalendar usually should be instantiated using
Calendar.getInstance(ULocale)
passing in a
ULocale
with the tag
"@calendar=chinese"
.
add
public void add(int field,
int amount)
Override Calendar to handle leap months properly.
- add in interface Calendar
getFieldResolutionTable
protected int[][][] getFieldResolutionTable()
Override Calendar to add IS_LEAP_MONTH to the field resolution
table.
- getFieldResolutionTable in interface Calendar
getType
public String getType()
Return the current Calendar type.
- getType in interface Calendar
- type of calendar (gregorian, etc.)
handleComputeFields
protected void handleComputeFields(int julianDay)
Override Calendar to compute several fields specific to the Chinese
calendar system. These are:
- ERA
- YEAR
- MONTH
- DAY_OF_MONTH
- DAY_OF_YEAR
- EXTENDED_YEAR
The DAY_OF_WEEK and DOW_LOCAL fields are already set when this
method is called. The getGregorianXxx() methods return Gregorian
calendar equivalents for the given Julian day.
Compute the ChineseCalendar-specific field IS_LEAP_MONTH.
- handleComputeFields in interface Calendar
handleComputeMonthStart
protected int handleComputeMonthStart(int eyear,
int month,
boolean useMonth)
Return the Julian day number of day before the first day of the
given month in the given extended year.
Note: This method reads the IS_LEAP_MONTH field to determine
whether the given month is a leap month.
- handleComputeMonthStart in interface Calendar
eyear
- the extended yearmonth
- the zero-based month. The month is also determined
by reading the IS_LEAP_MONTH field.
- the Julian day number of the day before the first
day of the given month and year
handleCreateFields
protected int[] handleCreateFields()
Override Calendar to allocate our additional field.
- handleCreateFields in interface Calendar
handleGetDateFormat
protected DateFormat handleGetDateFormat(String pattern,
ULocale locale)
Framework method to create a calendar-specific DateFormat object
using the the given pattern. This method is responsible for
creating the calendar- specific DateFormat and DateFormatSymbols
objects as needed.
- handleGetDateFormat in interface Calendar
handleGetExtendedYear
protected int handleGetExtendedYear()
Implement abstract Calendar method to return the extended year
defined by the current fields. This will use either the ERA and
YEAR field as the cycle and year-of-cycle, or the EXTENDED_YEAR
field as the continuous year count, depending on which is newer.
- handleGetExtendedYear in interface Calendar
handleGetLimit
protected int handleGetLimit(int field,
int limitType)
Override Calendar to return the limit value for the given field.
- handleGetLimit in interface Calendar
handleGetMonthLength
protected int handleGetMonthLength(int extendedYear,
int month)
Override Calendar method to return the number of days in the given
extended year and month.
Note: This method also reads the IS_LEAP_MONTH field to determine
whether or not the given month is a leap month.
- handleGetMonthLength in interface Calendar
roll
public void roll(int field,
int amount)
Override Calendar to handle leap months properly.
- roll in interface Calendar