Module java.base
Package java.time.chrono

Class JapaneseChronology

  • All Implemented Interfaces:
    Serializable, Comparable<Chronology>, Chronology

    public final class JapaneseChronology
extends AbstractChronology
implements Serializable
    The Japanese Imperial calendar system.

    This chronology defines the rules of the Japanese Imperial calendar system. 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.

    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.

    The supported ChronoField instances are:

    • DAY_OF_WEEK
    • DAY_OF_MONTH
    • DAY_OF_YEAR
    • EPOCH_DAY
    • MONTH_OF_YEAR
    • PROLEPTIC_MONTH
    • YEAR_OF_ERA
    • YEAR
    • ERA
    Implementation Requirements:
    This class is immutable and thread-safe.
    Since:
    1.8
    See Also:
    Serialized Form

    • Field Detail

      • INSTANCE

        public static final JapaneseChronology INSTANCE
        Singleton instance for Japanese chronology.

    • Method Detail

      • getId

        public String getId​()
        Gets the ID of the chronology - 'Japanese'.

        The ID uniquely identifies the Chronology. It can be used to lookup the Chronology using Chronology.of(String).

        Specified by:
        getId in interface Chronology
        Returns:
        the chronology ID - 'Japanese'
        See Also:
        getCalendarType()

      • getCalendarType

        public String getCalendarType​()
        Gets the calendar type of the underlying calendar system - 'japanese'.

        The calendar type is an identifier defined by the Unicode Locale Data Markup Language (LDML) specification. It can be used to lookup the Chronology using Chronology.of(String). It can also be used as part of a locale, accessible via Locale.getUnicodeLocaleType(String) with the key 'ca'.

        Specified by:
        getCalendarType in interface Chronology
        Returns:
        the calendar system type - 'japanese'
        See Also:
        getId()

      • date

        public JapaneseDate date​(Era era,
                         int yearOfEra,
                         int month,
                         int dayOfMonth)
        Obtains a local date in Japanese calendar system from the era, year-of-era, month-of-year and day-of-month fields.

        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
        Specified by:
        date in interface Chronology
        Parameters:
        era - the Japanese era, not null
        yearOfEra - the year-of-era
        month - the month-of-year
        dayOfMonth - the day-of-month
        Returns:
        the Japanese local date, not null
        Throws:
        DateTimeException - if unable to create the date
        ClassCastException - if the era is not a JapaneseEra

      • date

        public JapaneseDate date​(int prolepticYear,
                         int month,
                         int dayOfMonth)
        Obtains a local date in Japanese calendar system from the proleptic-year, month-of-year and day-of-month fields.

        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.

        Specified by:
        date in interface Chronology
        Parameters:
        prolepticYear - the proleptic-year
        month - the month-of-year
        dayOfMonth - the day-of-month
        Returns:
        the Japanese local date, not null
        Throws:
        DateTimeException - if unable to create the date

      • dateYearDay

        public JapaneseDate dateYearDay​(Era era,
                                int yearOfEra,
                                int dayOfYear)
        Obtains a local date in Japanese calendar system from the era, year-of-era and day-of-year fields.

        The day-of-year in this factory is expressed relative to the start of the year-of-era. This definition changes the normal meaning of day-of-year only in those years where the year-of-era is reset to one due to a change in the era. For example: 

          6th Jan Showa 64 = day-of-year 6
  7th Jan Showa 64 = day-of-year 7
  8th Jan Heisei 1 = day-of-year 1
  9th Jan Heisei 1 = day-of-year 2
        Specified by:
        dateYearDay in interface Chronology
        Parameters:
        era - the Japanese era, not null
        yearOfEra - the year-of-era
        dayOfYear - the day-of-year
        Returns:
        the Japanese local date, not null
        Throws:
        DateTimeException - if unable to create the date
        ClassCastException - if the era is not a JapaneseEra

      • dateYearDay

        public JapaneseDate dateYearDay​(int prolepticYear,
                                int dayOfYear)
        Obtains a local date in Japanese calendar system from the proleptic-year and day-of-year fields.

        The day-of-year in this factory is expressed relative to the start of the proleptic year. The Japanese proleptic year and day-of-year are the same as those in the ISO calendar system. They are not reset when the era changes.

        Specified by:
        dateYearDay in interface Chronology
        Parameters:
        prolepticYear - the proleptic-year
        dayOfYear - the day-of-year
        Returns:
        the Japanese local date, not null
        Throws:
        DateTimeException - if unable to create the date

      • dateEpochDay

        public JapaneseDate dateEpochDay​(long epochDay)
        Obtains a local date in the Japanese calendar system from the epoch-day.
        Specified by:
        dateEpochDay in interface Chronology
        Parameters:
        epochDay - the epoch day
        Returns:
        the Japanese local date, not null
        Throws:
        DateTimeException - if unable to create the date

      • dateNow

        public JapaneseDate dateNow​()
        Description copied from interface: Chronology
        Obtains the current local date in this chronology 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.

        Specified by:
        dateNow in interface Chronology
        Returns:
        the current local date using the system clock and default time-zone, not null

      • dateNow

        public JapaneseDate dateNow​(ZoneId zone)
        Description copied from interface: Chronology
        Obtains the current local date in this chronology 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.

        Specified by:
        dateNow in interface Chronology
        Parameters:
        zone - the zone ID to use, not null
        Returns:
        the current local date using the system clock, not null

      • dateNow

        public JapaneseDate dateNow​(Clock clock)
        Description copied from interface: Chronology
        Obtains the current local date in this chronology 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.

        Specified by:
        dateNow in interface Chronology
        Parameters:
        clock - the clock to use, not null
        Returns:
        the current local date, not null

      • date

        public JapaneseDate date​(TemporalAccessor temporal)
        Description copied from interface: Chronology
        Obtains a local date in this chronology from another temporal object.

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

        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, aChronology::date.

        Specified by:
        date in interface Chronology
        Parameters:
        temporal - the temporal object to convert, not null
        Returns:
        the local date in this chronology, not null
        See Also:
        ChronoLocalDate.from(TemporalAccessor)

      • localDateTime

        public ChronoLocalDateTime<JapaneseDate> localDateTime​(TemporalAccessor temporal)
        Description copied from interface: Chronology
        Obtains a local date-time in this chronology from another temporal object.

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

        The conversion extracts and combines the ChronoLocalDate and the LocalTime from the temporal object. Implementations are permitted to perform optimizations such as accessing those fields that are equivalent to the relevant objects. The result uses this chronology.

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

        Specified by:
        localDateTime in interface Chronology
        Parameters:
        temporal - the temporal object to convert, not null
        Returns:
        the local date-time in this chronology, not null
        See Also:
        ChronoLocalDateTime.from(TemporalAccessor)

      • zonedDateTime

        public ChronoZonedDateTime<JapaneseDate> zonedDateTime​(TemporalAccessor temporal)
        Description copied from interface: Chronology
        Obtains a ChronoZonedDateTime in this chronology from another temporal object.

        This obtains a zoned date-time in this chronology based on the specified temporal. A TemporalAccessor represents an arbitrary set of date and time information, which this factory converts to an instance of ChronoZonedDateTime.

        The conversion will first obtain a ZoneId from the temporal object, falling back to a ZoneOffset if necessary. It will then try to obtain an Instant, falling back to a ChronoLocalDateTime if necessary. The result will be either the combination of ZoneId or ZoneOffset with Instant or ChronoLocalDateTime. Implementations are permitted to perform optimizations such as accessing those fields that are equivalent to the relevant objects. The result uses this chronology.

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

        Specified by:
        zonedDateTime in interface Chronology
        Parameters:
        temporal - the temporal object to convert, not null
        Returns:
        the zoned date-time in this chronology, not null
        See Also:
        ChronoZonedDateTime.from(TemporalAccessor)

      • zonedDateTime

        public ChronoZonedDateTime<JapaneseDate> zonedDateTime​(Instant instant,
                                                       ZoneId zone)
        Description copied from interface: Chronology
        Obtains a ChronoZonedDateTime in this chronology from an Instant.

        This obtains a zoned date-time with the same instant as that specified.

        Specified by:
        zonedDateTime in interface Chronology
        Parameters:
        instant - the instant to create the date-time from, not null
        zone - the time-zone, not null
        Returns:
        the zoned date-time, not null

      • isLeapYear

        public boolean isLeapYear​(long prolepticYear)
        Checks if the specified year is a leap year.

        Japanese calendar leap years occur exactly in line with ISO leap years. This method does not validate the year passed in, and only has a well-defined result for years in the supported range.

        Specified by:
        isLeapYear in interface Chronology
        Parameters:
        prolepticYear - the proleptic-year to check, not validated for range
        Returns:
        true if the year is a leap year

      • prolepticYear

        public int prolepticYear​(Era era,
                         int yearOfEra)
        Description copied from interface: Chronology
        Calculates the proleptic-year given the era and year-of-era.

        This combines the era and year-of-era into the single proleptic-year field.

        If the chronology makes active use of eras, such as JapaneseChronology then the year-of-era will be validated against the era. For other chronologies, validation is optional.

        Specified by:
        prolepticYear in interface Chronology
        Parameters:
        era - the era of the correct type for the chronology, not null
        yearOfEra - the chronology year-of-era
        Returns:
        the proleptic-year

      • eras

        public List<Era> eras​()
        Description copied from interface: Chronology
        Gets the list of eras for the chronology.

        Most calendar systems have an era, within which the year has meaning. If the calendar system does not support the concept of eras, an empty list must be returned.

        Specified by:
        eras in interface Chronology
        Returns:
        the list of eras for the chronology, may be immutable, not null

      • range

        public ValueRange range​(ChronoField field)
        Description copied from interface: Chronology
        Gets the range of valid values for the specified field.

        All fields can be expressed as a long integer. This method returns an object that describes the valid range for that value.

        Note that the result only describes the minimum and maximum valid values and it is important not to read too much into them. For example, there could be values within the range that are invalid for the field.

        This method will return a result whether or not the chronology supports the field.

        Specified by:
        range in interface Chronology
        Parameters:
        field - the field to get the range for, not null
        Returns:
        the range of valid values for the field, not null

      • resolveDate

        public JapaneseDate resolveDate​(Map<TemporalField,Long> fieldValues,
                                ResolverStyle resolverStyle)
        Description copied from class: AbstractChronology
        Resolves parsed ChronoField values into a date during parsing.

        Most TemporalField implementations are resolved using the resolve method on the field. By contrast, the ChronoField class defines fields that only have meaning relative to the chronology. As such, ChronoField date fields are resolved here in the context of a specific chronology.

        ChronoField instances are resolved by this method, which may be overridden in subclasses.

        • EPOCH_DAY - If present, this is converted to a date and all other date fields are then cross-checked against the date.
        • PROLEPTIC_MONTH - If present, then it is split into the YEAR and MONTH_OF_YEAR. If the mode is strict or smart then the field is validated.
        • YEAR_OF_ERA and ERA - If both are present, then they are combined to form a YEAR. In lenient mode, the YEAR_OF_ERA range is not validated, in smart and strict mode it is. The ERA is validated for range in all three modes. If only the YEAR_OF_ERA is present, and the mode is smart or lenient, then the last available era is assumed. In strict mode, no era is assumed and the YEAR_OF_ERA is left untouched. If only the ERA is present, then it is left untouched.
        • YEAR, MONTH_OF_YEAR and DAY_OF_MONTH - If all three are present, then they are combined to form a date. In all three modes, the YEAR is validated. If the mode is smart or strict, then the month and day are validated. If the mode is lenient, then the date is combined in a manner equivalent to creating a date on the first day of the first month in the requested year, then adding the difference in months, then the difference in days. If the mode is smart, and the day-of-month is greater than the maximum for the year-month, then the day-of-month is adjusted to the last day-of-month. If the mode is strict, then the three fields must form a valid date.
        • YEAR and DAY_OF_YEAR - If both are present, then they are combined to form a date. In all three modes, the YEAR is validated. If the mode is lenient, then the date is combined in a manner equivalent to creating a date on the first day of the requested year, then adding the difference in days. If the mode is smart or strict, then the two fields must form a valid date.
        • YEAR, MONTH_OF_YEAR, ALIGNED_WEEK_OF_MONTH and ALIGNED_DAY_OF_WEEK_IN_MONTH - If all four are present, then they are combined to form a date. In all three modes, the YEAR is validated. If the mode is lenient, then the date is combined in a manner equivalent to creating a date on the first day of the first month in the requested year, then adding the difference in months, then the difference in weeks, then in days. If the mode is smart or strict, then the all four fields are validated to their outer ranges. The date is then combined in a manner equivalent to creating a date on the first day of the requested year and month, then adding the amount in weeks and days to reach their values. If the mode is strict, the date is additionally validated to check that the day and week adjustment did not change the month.
        • YEAR, MONTH_OF_YEAR, ALIGNED_WEEK_OF_MONTH and DAY_OF_WEEK - If all four are present, then they are combined to form a date. The approach is the same as described above for years, months and weeks in ALIGNED_DAY_OF_WEEK_IN_MONTH. The day-of-week is adjusted as the next or same matching day-of-week once the years, months and weeks have been handled.
        • YEAR, ALIGNED_WEEK_OF_YEAR and ALIGNED_DAY_OF_WEEK_IN_YEAR - If all three are present, then they are combined to form a date. In all three modes, the YEAR is validated. If the mode is lenient, then the date is combined in a manner equivalent to creating a date on the first day of the requested year, then adding the difference in weeks, then in days. If the mode is smart or strict, then the all three fields are validated to their outer ranges. The date is then combined in a manner equivalent to creating a date on the first day of the requested year, then adding the amount in weeks and days to reach their values. If the mode is strict, the date is additionally validated to check that the day and week adjustment did not change the year.
        • YEAR, ALIGNED_WEEK_OF_YEAR and DAY_OF_WEEK - If all three are present, then they are combined to form a date. The approach is the same as described above for years and weeks in ALIGNED_DAY_OF_WEEK_IN_YEAR. The day-of-week is adjusted as the next or same matching day-of-week once the years and weeks have been handled.

        The default implementation is suitable for most calendar systems. If ChronoField.YEAR_OF_ERA is found without an ChronoField.ERA then the last era in Chronology.eras() is used. The implementation assumes a 7 day week, that the first day-of-month has the value 1, that first day-of-year has the value 1, and that the first of the month and year always exists.

        Specified by:
        resolveDate in interface Chronology
        Overrides:
        resolveDate in class AbstractChronology
        Parameters:
        fieldValues - the map of fields to values, which can be updated, not null
        resolverStyle - the requested type of resolve, not null
        Returns:
        the resolved date, null if insufficient information to create a date