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 Details

    • 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​(TemporalField field, long newValue)
      Description copied from interface: ChronoLocalDate
      Returns an object of the same type as this object with the specified field altered.

      This returns a new object based on this one with the value for the specified field changed. For example, on a LocalDate, this could be used to set the year, month or day-of-month. The returned object will have the same observable type as this object.

      In some cases, changing a field is not fully defined. For example, if the target object is a date representing the 31st January, then changing the month to February would be unclear. In cases like this, the field is responsible for resolving the result. Typically it will choose the previous valid date, which would be the last valid day of February in this example.

      Specified by:
      with in interface ChronoLocalDate
      Specified by:
      with in interface Temporal
      Parameters:
      field - the field to set in the result, not null
      newValue - the new value of the field in the result
      Returns:
      an object of the same type with the specified field set, not null

    • 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

    • plus

      public JapaneseDate plus​(long amountToAdd, TemporalUnit unit)
      Description copied from interface: ChronoLocalDate
      Returns an object of the same type as this object with the specified period added.

      This method returns a new object based on this one with the specified period added. For example, on a LocalDate, this could be used to add a number of years, months or days. The returned object will have the same observable type as this object.

      In some cases, changing a field is not fully defined. For example, if the target object is a date representing the 31st January, then adding one month would be unclear. In cases like this, the field is responsible for resolving the result. Typically it will choose the previous valid date, which would be the last valid day of February in this example.

      Specified by:
      plus in interface ChronoLocalDate
      Specified by:
      plus in interface Temporal
      Parameters:
      amountToAdd - the amount of the specified unit to add, may be negative
      unit - the unit of the amount to add, not null
      Returns:
      an object of the same type with the specified period added, not null

    • minus

      public JapaneseDate minus​(long amountToAdd, TemporalUnit unit)
      Description copied from interface: ChronoLocalDate
      Returns an object of the same type as this object with the specified period subtracted.

      This method returns a new object based on this one with the specified period subtracted. For example, on a LocalDate, this could be used to subtract a number of years, months or days. The returned object will have the same observable type as this object.

      In some cases, changing a field is not fully defined. For example, if the target object is a date representing the 31st March, then subtracting one month would be unclear. In cases like this, the field is responsible for resolving the result. Typically it will choose the previous valid date, which would be the last valid day of February in this example.

      Specified by:
      minus in interface ChronoLocalDate
      Specified by:
      minus in interface Temporal
      Parameters:
      amountToAdd - the amount of the specified unit to subtract, may be negative
      unit - the unit of the amount to subtract, not null
      Returns:
      an object of the same type with the specified period subtracted, not null

    • atTime

      public final ChronoLocalDateTime<JapaneseDate> atTime​(LocalTime localTime)
      Description copied from interface: ChronoLocalDate
      Combines this date with a time to create a ChronoLocalDateTime.

      This returns a ChronoLocalDateTime formed from this date at the specified time. All possible combinations of date and time are valid.

      Specified by:
      atTime in interface ChronoLocalDate
      Parameters:
      localTime - the local time to use, not null
      Returns:
      the local date-time formed from this date and the specified time, not null

    • 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.