Module java.base

Package java.time.chrono

Class JapaneseDate

java.lang.Object

java.time.chrono.JapaneseDate

All Implemented Interfaces:

Serializable, Comparable<ChronoLocalDate>, ChronoLocalDate, Temporal, TemporalAccessor, TemporalAdjuster

public final class JapaneseDate
extends Object
implements ChronoLocalDate, Serializable

A date in the Japanese Imperial calendar system.

This date operates using the Japanese Imperial calendar. This calendar system is primarily used in Japan.

The Japanese Imperial calendar system is the same as the ISO calendar system apart from the era-based year numbering. The proleptic-year is defined to be equal to the ISO proleptic-year.

Japan introduced the Gregorian calendar starting with Meiji 6. Only Meiji and later eras are supported; dates before Meiji 6, January 1 are not supported.

For example, the Japanese year "Heisei 24" corresponds to ISO year "2012".
Calling japaneseDate.get(YEAR_OF_ERA) will return 24.
Calling japaneseDate.get(YEAR) will return 2012.
Calling japaneseDate.get(ERA) will return 2, corresponding to JapaneseChronology.ERA_HEISEI.

This is a value-based class; use of identity-sensitive operations (including reference equality (==), identity hash code, or synchronization) on instances of JapaneseDate may have unpredictable results and should be avoided. The equals method should be used for comparisons.

Implementation Requirements:

This class is immutable and thread-safe.

Since:

1.8

See Also:

Serialized Form

Method Summary

Modifier and Type	Method	Description
boolean	equals(Object obj)	Compares this date to another date, including the chronology.
static JapaneseDate	from(TemporalAccessor temporal)	Obtains a JapaneseDate from a temporal object.
JapaneseChronology	getChronology()	Gets the chronology of this date, which is the Japanese calendar system.
JapaneseEra	getEra()	Gets the era applicable at this date.
int	hashCode()	A hash code for this date.
boolean	isSupported(TemporalField field)	Checks if the specified field is supported.
int	lengthOfMonth()	Returns the length of the month represented by this date.
JapaneseDate	minus(TemporalAmount amount)	Returns an object of the same type as this object with an amount subtracted.
static JapaneseDate	now()	Obtains the current JapaneseDate from the system clock in the default time-zone.
static JapaneseDate	now(Clock clock)	Obtains the current JapaneseDate from the specified clock.
static JapaneseDate	now(ZoneId zone)	Obtains the current JapaneseDate from the system clock in the specified time-zone.
static JapaneseDate	of(int prolepticYear, int month, int dayOfMonth)	Obtains a JapaneseDate representing a date in the Japanese calendar system from the proleptic-year, month-of-year and day-of-month fields.
static JapaneseDate	of(JapaneseEra era, int yearOfEra, int month, int dayOfMonth)	Obtains a JapaneseDate representing a date in the Japanese calendar system from the era, year-of-era, month-of-year and day-of-month fields.
JapaneseDate	plus(TemporalAmount amount)	Returns an object of the same type as this object with an amount added.
String	toString()	Returns a string representation of the object.
long	until(Temporal endExclusive, TemporalUnit unit)	Calculates the amount of time until another date in terms of the specified unit.
JapaneseDate	with(TemporalAdjuster adjuster)	Returns an adjusted object of the same type as this object with the adjustment made.

Methods declared in class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods declared in interface java.time.chrono.ChronoLocalDate

adjustInto, atTime, compareTo, format, isAfter, isBefore, isEqual, isLeapYear, isSupported, lengthOfYear, minus, plus, query, toEpochDay, toString, until, until, with

Methods declared in interface java.time.temporal.TemporalAccessor

get, getLong, range

Method Detail

now

public static JapaneseDate now()

Obtains the current JapaneseDate from the system clock in the default time-zone.

This will query the system clock in the default time-zone to obtain the current date.

Using this method will prevent the ability to use an alternate clock for testing because the clock is hard-coded.

Returns:

the current date using the system clock and default time-zone, not null

now

public static JapaneseDate now(ZoneId zone)

Obtains the current JapaneseDate from the system clock in the specified time-zone.

This will query the system clock to obtain the current date. Specifying the time-zone avoids dependence on the default time-zone.

Using this method will prevent the ability to use an alternate clock for testing because the clock is hard-coded.

Parameters:

zone - the zone ID to use, not null

Returns:

the current date using the system clock, not null

now

public static JapaneseDate now(Clock clock)

Obtains the current JapaneseDate from the specified clock.

This will query the specified clock to obtain the current date - today. Using this method allows the use of an alternate clock for testing. The alternate clock may be introduced using dependency injection.

Parameters:

clock - the clock to use, not null

Returns:

the current date, not null

Throws:

DateTimeException - if the current date cannot be obtained

of

public static JapaneseDate of(JapaneseEra era,
                              int yearOfEra,
                              int month,
                              int dayOfMonth)

Obtains a JapaneseDate representing a date in the Japanese calendar system from the era, year-of-era, month-of-year and day-of-month fields.

This returns a JapaneseDate with the specified fields. The day must be valid for the year and month, otherwise an exception will be thrown.

The Japanese month and day-of-month are the same as those in the ISO calendar system. They are not reset when the era changes. For example:

  6th Jan Showa 64 = ISO 1989-01-06
  7th Jan Showa 64 = ISO 1989-01-07
  8th Jan Heisei 1 = ISO 1989-01-08
  9th Jan Heisei 1 = ISO 1989-01-09
 

Parameters:

era - the Japanese era, not null

yearOfEra - the Japanese year-of-era

month - the Japanese month-of-year, from 1 to 12

dayOfMonth - the Japanese day-of-month, from 1 to 31

Returns:

the date in Japanese calendar system, not null

Throws:

DateTimeException - if the value of any field is out of range, or if the day-of-month is invalid for the month-year, or if the date is not a Japanese era

of

public static JapaneseDate of(int prolepticYear,
                              int month,
                              int dayOfMonth)

Obtains a JapaneseDate representing a date in the Japanese calendar system from the proleptic-year, month-of-year and day-of-month fields.

This returns a JapaneseDate with the specified fields. The day must be valid for the year and month, otherwise an exception will be thrown.

The Japanese proleptic year, month and day-of-month are the same as those in the ISO calendar system. They are not reset when the era changes.

Parameters:

prolepticYear - the Japanese proleptic-year

month - the Japanese month-of-year, from 1 to 12

dayOfMonth - the Japanese day-of-month, from 1 to 31

Returns:

the date in Japanese calendar system, not null

Throws:

DateTimeException - if the value of any field is out of range, or if the day-of-month is invalid for the month-year

from

public static JapaneseDate from(TemporalAccessor temporal)

Obtains a JapaneseDate from a temporal object.

This obtains a date in the Japanese calendar system based on the specified temporal. A TemporalAccessor represents an arbitrary set of date and time information, which this factory converts to an instance of JapaneseDate.

The conversion typically uses the EPOCH_DAY field, which is standardized across calendar systems.

This method matches the signature of the functional interface TemporalQuery allowing it to be used as a query via method reference, JapaneseDate::from.

Parameters:

temporal - the temporal object to convert, not null

Returns:

the date in Japanese calendar system, not null

Throws:

DateTimeException - if unable to convert to a JapaneseDate

See Also:

Chronology.date(TemporalAccessor)

getChronology

public JapaneseChronology getChronology()

Gets the chronology of this date, which is the Japanese calendar system.

The Chronology represents the calendar system in use. The era and other fields in ChronoField are defined by the chronology.

Specified by:

getChronology in interface ChronoLocalDate

Returns:

the Japanese chronology, not null

getEra

public JapaneseEra getEra()

Gets the era applicable at this date.

The Japanese calendar system has multiple eras defined by JapaneseEra.

Specified by:

getEra in interface ChronoLocalDate

Returns:

the era applicable at this date, not null

lengthOfMonth

public int lengthOfMonth()

Returns the length of the month represented by this date.

This returns the length of the month in days. Month lengths match those of the ISO calendar system.

Specified by:

lengthOfMonth in interface ChronoLocalDate

Returns:

the length of the month in days

isSupported

public boolean isSupported(TemporalField field)

Checks if the specified field is supported.

This checks if this date can be queried for the specified field. If false, then calling the range and get methods will throw an exception.

If the field is a ChronoField then the query is implemented here. The supported fields are:

• DAY_OF_WEEK
• DAY_OF_MONTH
• DAY_OF_YEAR
• EPOCH_DAY
• MONTH_OF_YEAR
• PROLEPTIC_MONTH
• YEAR_OF_ERA
• YEAR
• ERA

All other ChronoField instances will return false.

If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.isSupportedBy(TemporalAccessor) passing this as the argument. Whether the field is supported is determined by the field.

Specified by:

isSupported in interface ChronoLocalDate

Specified by:

isSupported in interface TemporalAccessor

Parameters:

field - the field to check, null returns false

Returns:

true if the field is supported on this date, false if not

with

public JapaneseDate with(TemporalAdjuster adjuster)

Returns an adjusted object of the same type as this object with the adjustment made.

This adjusts this date-time according to the rules of the specified adjuster. A simple adjuster might simply set the one of the fields, such as the year field. A more complex adjuster might set the date to the last day of the month. A selection of common adjustments is provided in TemporalAdjusters. These include finding the "last day of the month" and "next Wednesday". The adjuster is responsible for handling special cases, such as the varying lengths of month and leap years.

Some example code indicating how and why this method is used:

  date = date.with(Month.JULY);        // most key classes implement TemporalAdjuster
  date = date.with(lastDayOfMonth());  // static import from Adjusters
  date = date.with(next(WEDNESDAY));   // static import from Adjusters and DayOfWeek
 

Specified by:

with in interface ChronoLocalDate

Specified by:

with in interface Temporal

Parameters:

adjuster - the adjuster to use, not null

Returns:

an object of the same type with the specified adjustment made, not null

Throws:

DateTimeException - if unable to make the adjustment

ArithmeticException - if numeric overflow occurs

plus

public JapaneseDate plus(TemporalAmount amount)

Returns an object of the same type as this object with an amount added.

This adjusts this temporal, adding according to the rules of the specified amount. The amount is typically a Period but may be any other type implementing the TemporalAmount interface, such as Duration.

Some example code indicating how and why this method is used:

  date = date.plus(period);                // add a Period instance
  date = date.plus(duration);              // add a Duration instance
  date = date.plus(workingDays(6));        // example user-written workingDays method
 

Note that calling plus followed by minus is not guaranteed to return the same date-time.

Specified by:

plus in interface ChronoLocalDate

Specified by:

plus in interface Temporal

Parameters:

amount - the amount to add, not null

Returns:

an object of the same type with the specified adjustment made, not null

Throws:

DateTimeException - if the addition cannot be made

ArithmeticException - if numeric overflow occurs

minus

public JapaneseDate minus(TemporalAmount amount)

Returns an object of the same type as this object with an amount subtracted.

This adjusts this temporal, subtracting according to the rules of the specified amount. The amount is typically a Period but may be any other type implementing the TemporalAmount interface, such as Duration.

Some example code indicating how and why this method is used:

  date = date.minus(period);               // subtract a Period instance
  date = date.minus(duration);             // subtract a Duration instance
  date = date.minus(workingDays(6));       // example user-written workingDays method
 

Note that calling plus followed by minus is not guaranteed to return the same date-time.

Specified by:

minus in interface ChronoLocalDate

Specified by:

minus in interface Temporal

Parameters:

amount - the amount to subtract, not null

Returns:

an object of the same type with the specified adjustment made, not null

Throws:

DateTimeException - if the subtraction cannot be made

ArithmeticException - if numeric overflow occurs

equals

public boolean equals(Object obj)

Compares this date to another date, including the chronology.

Compares this JapaneseDate with another ensuring that the date is the same.

Only objects of type JapaneseDate are compared, other types return false. To compare the dates of two TemporalAccessor instances, including dates in two different chronologies, use ChronoField.EPOCH_DAY as a comparator.

Specified by:

equals in interface ChronoLocalDate

Parameters:

obj - the object to check, null returns false

Returns:

true if this is equal to the other date

See Also:

Object.hashCode(), HashMap

hashCode

public int hashCode()

A hash code for this date.

Specified by:

hashCode in interface ChronoLocalDate

Returns:

a suitable hash code based only on the Chronology and the date

See Also:

Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

until

public long until(Temporal endExclusive,
                  TemporalUnit unit)

Description copied from interface: ChronoLocalDate

Calculates the amount of time until another date in terms of the specified unit.

This calculates the amount of time between two ChronoLocalDate objects in terms of a single TemporalUnit. The start and end points are this and the specified date. The result will be negative if the end is before the start. The Temporal passed to this method is converted to a ChronoLocalDate using Chronology.date(TemporalAccessor). The calculation returns a whole number, representing the number of complete units between the two dates. For example, the amount in days between two dates can be calculated using startDate.until(endDate, DAYS).

There are two equivalent ways of using this method. The first is to invoke this method. The second is to use TemporalUnit.between(Temporal, Temporal):

   // these two lines are equivalent
   amount = start.until(end, MONTHS);
   amount = MONTHS.between(start, end);
 

The choice should be made based on which makes the code more readable.

The calculation is implemented in this method for ChronoUnit. The units DAYS, WEEKS, MONTHS, YEARS, DECADES, CENTURIES, MILLENNIA and ERAS should be supported by all implementations. Other ChronoUnit values will throw an exception.

If the unit is not a ChronoUnit, then the result of this method is obtained by invoking TemporalUnit.between(Temporal, Temporal) passing this as the first argument and the converted input temporal as the second argument.

This instance is immutable and unaffected by this method call.

Specified by:

until in interface ChronoLocalDate

Specified by:

until in interface Temporal

Parameters:

endExclusive - the end date, exclusive, which is converted to a ChronoLocalDate in the same chronology, not null

unit - the unit to measure the amount in, not null

Returns:

the amount of time between this date and the end date

toString

public String toString()

Description copied from class: Object

Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

 getClass().getName() + '@' + Integer.toHexString(hashCode())
 

Specified by:

toString in interface ChronoLocalDate

Overrides:

toString in class Object

Returns:

a string representation of the object.