Class Year

  • All Implemented Interfaces:
    Serializable, Comparable<Year>, Calendrical, CalendricalMatcher, DateAdjuster

    public final class Year
    extends Object
    implements Calendrical, Comparable<Year>, Serializable, DateAdjuster, CalendricalMatcher
    A year in the ISO-8601 calendar system, such as 2007.

    Year is an immutable calendrical that represents a year. Any field that can be derived from a year can be obtained.

    Note that years in the ISO chronology only align with years in the Gregorian-Julian system for modern years. Parts of Russia did not switch to the modern Gregorian/ISO rules until 1920. As such, historical years must be treated with caution.

    This class does not store or represent a month, day, time or time-zone. Thus, for example, the value "2007" can be stored in a Year.

    Years represented by this class follow the ISO-8601 standard and use the proleptic numbering system. Year 1 is preceded by year 0, then by year -1.

    The ISO-8601 calendar system is the modern civil calendar system used today in most of the world. It is equivalent to the proleptic Gregorian calendar system, in which todays's rules for leap years are applied for all time. For most applications written today, the ISO-8601 rules are entirely suitable. Any application that uses historical dates should consider using HistoricDate.

    Year is immutable and thread-safe.

    Author:
    Michael Nascimento Santos, Stephen Colebourne
    See Also:
    Serialized Form
    • Field Summary

      Fields 
      Modifier and Type Field Description
      static int MAX_YEAR
      Constant for the maximum year on the proleptic ISO calendar system, 999,999,999.
      static int MIN_YEAR
      Constant for the minimum year on the proleptic ISO calendar system, -999,999,999.
    • Field Detail

      • MIN_YEAR

        public static final int MIN_YEAR
        Constant for the minimum year on the proleptic ISO calendar system, -999,999,999.
        See Also:
        Constant Field Values
      • MAX_YEAR

        public static final int MAX_YEAR
        Constant for the maximum year on the proleptic ISO calendar system, 999,999,999.
        See Also:
        Constant Field Values
    • Method Detail

      • rule

        public static DateTimeFieldRule<Integer> rule()
        Gets the rule that defines how the year field operates.

        The rule provides access to the minimum and maximum values, and a generic way to access values within a calendrical.

        Returns:
        the year rule, never null
      • now

        public static Year now()
        Obtains the current year from the system clock in the default time-zone.

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

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

        Returns:
        the current year using the system clock, never null
      • now

        public static Year now​(Clock clock)
        Obtains the current year from the specified clock.

        This will query the specified clock to obtain the current year. 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 year, never null
      • of

        public static Year of​(int isoYear)
        Obtains an instance of Year.

        This method accepts a year value from the proleptic ISO calendar system.

        The year 2AD/CE is represented by 2.
        The year 1AD/CE is represented by 1.
        The year 1BC/BCE is represented by 0.
        The year 2BC/BCE is represented by -1.

        Parameters:
        isoYear - the ISO proleptic year to represent, from MIN_YEAR to MAX_YEAR
        Returns:
        the created Year, never null
        Throws:
        IllegalCalendarFieldValueException - if the field is invalid
      • of

        public static Year of​(Calendrical calendrical)
        Obtains an instance of Year from a calendrical.

        This can be used extract the year value directly from any implementation of Calendrical, including those in other calendar systems.

        Parameters:
        calendrical - the calendrical to extract from, not null
        Returns:
        the Year instance, never null
        Throws:
        UnsupportedRuleException - if the year cannot be obtained
      • getValue

        public int getValue()
        Gets the year value.
        Returns:
        the year, from MIN_YEAR to MAX_YEAR
      • get

        public <T> T get​(CalendricalRule<T> rule)
        Gets the value of the specified calendrical rule.

        This method queries the value of the specified calendrical rule. If the value cannot be returned for the rule from this instance then null will be returned.

        Specified by:
        get in interface Calendrical
        Parameters:
        rule - the rule to use, not null
        Returns:
        the value for the rule, null if the value cannot be returned
      • isLeap

        public boolean isLeap()
        Checks if the year is a leap year, according to the ISO proleptic calendar system rules.

        This method applies the current rules for leap years across the whole time-line. In general, a year is a leap year if it is divisible by four without remainder. However, years divisible by 100, are not leap years, with the exception of years divisible by 400 which are.

        For example, 1904 is a leap year it is divisible by 4. 1900 was not a leap year as it is divisible by 100, however 2000 was a leap year as it is divisible by 400.

        The calculation is proleptic - applying the same rules into the far future and far past. This is historically inaccurate, but is correct for the ISO8601 standard.

        Returns:
        true if the year is leap, false otherwise
      • next

        public Year next()
        Returns the next year.
        Returns:
        the next year, never null
        Throws:
        CalendricalException - if the maximum year is reached
      • nextLeap

        public Year nextLeap()
        Returns the next leap year after the current year. The definition of a leap year is specified in isLeap().
        Returns:
        the next leap year after this year, never null
        Throws:
        CalendricalException - if the maximum year is reached
      • previous

        public Year previous()
        Returns the previous year.
        Returns:
        the previous year, never null
        Throws:
        CalendricalException - if the maximum year is reached
      • previousLeap

        public Year previousLeap()
        Returns the previous leap year before the current year. The definition of a leap year is specified in isLeap().
        Returns:
        the previous leap year after this year, never null
        Throws:
        CalendricalException - if the minimum year is reached
      • plus

        public Year plus​(PeriodProvider periodProvider)
        Returns a copy of this Year with the specified period added.

        This adds the specified period to this year, returning a new year. Before addition, the period is converted to a Period using Period.of(PeriodProvider). The calculation simply adds the amount of years from the specified period. ISO fields other than years are ignored.

        Note that no normalization is performed. Thus, adding 24 months has no effect. To take months into account, the period must be normalized by the caller.

        This instance is immutable and unaffected by this method call.

        Parameters:
        periodProvider - the period to add, not null
        Returns:
        a Year based on this year with the period added, never null
        Throws:
        CalendricalException - if the specified period cannot be converted to a Period
        ArithmeticException - if the result exceeds the supported year range
      • plusYears

        public Year plusYears​(long years)
        Returns a copy of this Year with the specified number of years added.

        This instance is immutable and unaffected by this method call.

        Parameters:
        years - the years to add
        Returns:
        a Year based on this year with the period added, never null
        Throws:
        CalendricalException - if the result exceeds the supported year range
      • minus

        public Year minus​(PeriodProvider periodProvider)
        Returns a copy of this Year with the specified period subtracted.

        This subtracts the specified period from this year, returning a new year. Before subtraction, the period is converted to a Period using Period.of(PeriodProvider). The calculation simply adds the amount of years from the specified period. ISO fields other than years are ignored.

        Note that no normalization is performed. Thus, subtracting 24 months has no effect. To take months into account, the period must be normalized by the caller.

        This instance is immutable and unaffected by this method call.

        Parameters:
        periodProvider - the period to subtract, not null
        Returns:
        a Year based on this year with the period subtracted, never null
        Throws:
        CalendricalException - if the specified period cannot be converted to a Period
        ArithmeticException - if the result exceeds the supported year range
      • minusYears

        public Year minusYears​(long years)
        Returns a copy of this Year with the specified number of years subtracted.

        This instance is immutable and unaffected by this method call.

        Parameters:
        years - the years to subtract
        Returns:
        a Year based on this year with the period subtracted, never null
        Throws:
        CalendricalException - if the result exceeds the supported year range
      • adjustDate

        public LocalDate adjustDate​(LocalDate date)
        Adjusts a date to have the value of this year, returning a new date.

        This method implements the DateAdjuster interface. It is intended that, instead of calling this method directly, it is used from an instance of LocalDate:

           date = date.with(year);
         

        This implementation handles the case where the date represents February 29 and this is not a leap year using the DateResolvers.previousValid() resolver.

        This instance is immutable and unaffected by this method call.

        Specified by:
        adjustDate in interface DateAdjuster
        Parameters:
        date - the date to be adjusted, not null
        Returns:
        the adjusted date, never null
      • adjustDate

        public LocalDate adjustDate​(LocalDate date,
                                    DateResolver resolver)
        Adjusts a date to have the value of this year, using a resolver to handle the case when the day-of-month becomes invalid.

        This instance is immutable and unaffected by this method call.

        Parameters:
        date - the date to be adjusted, not null
        resolver - the date resolver to use if the day-of-month becomes invalid, not null
        Returns:
        the adjusted date, never null
        Throws:
        IllegalCalendarFieldValueException - if the date cannot be resolved using the resolver
      • lengthInDays

        public int lengthInDays()
        Gets the length of this year in days.
        Returns:
        the length of this year in days, 365 or 366
      • isValidMonthDay

        public boolean isValidMonthDay​(MonthDay monthDay)
        Checks if the month-day is valid for this year.

        This method checks whether this year and the input month and day form a valid date.

        Parameters:
        monthDay - the month-day to validate, null returns false
        Returns:
        true if the month and day are valid for this year
      • atMonth

        public YearMonth atMonth​(MonthOfYear monthOfYear)
        Returns a year-month formed from this year at the specified month.

        This method merges this and the specified month to form an instance of YearMonth. This method can be used as part of a chain to produce a date:

         LocalDate date = year.atMonth(month).atDay(day);
         

        This instance is immutable and unaffected by this method call.

        Parameters:
        monthOfYear - the month-of-year to use, not null
        Returns:
        the year-month formed from this year and the specified month, never null
      • atMonth

        public YearMonth atMonth​(int monthOfYear)
        Returns a year-month formed from this year at the specified month.

        This method merges this and the specified month to form an instance of YearMonth. This method can be used as part of a chain to produce a date:

         LocalDate date = year.atMonth(month).atDay(day);
         

        This instance is immutable and unaffected by this method call.

        Parameters:
        monthOfYear - the month-of-year to use, from 1 (January) to 12 (December)
        Returns:
        the year-month formed from this year and the specified month, never null
      • atMonthDay

        public LocalDate atMonthDay​(MonthDay monthDay)
        Returns a date formed from this year at the specified month-day.

        This merges the two objects - this and the specified day - to form an instance of LocalDate.

         LocalDate date = year.atMonthDay(monthDay);
         

        This instance is immutable and unaffected by this method call.

        Parameters:
        monthDay - the month-day to use, not null
        Returns:
        the local date formed from this year and the specified month-day, never null
        Throws:
        InvalidCalendarFieldException - if the month-day is February 29th and this is not a leap year
      • atDay

        public LocalDate atDay​(int dayOfYear)
        Returns a date formed from this year at the specified day-of-year.

        This merges the two objects - this and the specified day - to form an instance of LocalDate.

         LocalDate date = year.atDay(dayOfYear);
         

        This instance is immutable and unaffected by this method call.

        Parameters:
        dayOfYear - the day-of-year to use, not null
        Returns:
        the local date formed from this year and the specified date of year, never null
        Throws:
        InvalidCalendarFieldException - if the day of year is 366 and this is not a leap year
      • compareTo

        public int compareTo​(Year other)
        Compares this year to another year.
        Specified by:
        compareTo in interface Comparable<Year>
        Parameters:
        other - the other year to compare to, not null
        Returns:
        the comparator value, negative if less, positive if greater
        Throws:
        NullPointerException - if other is null
      • isAfter

        public boolean isAfter​(Year other)
        Is this year after the specified year.
        Parameters:
        other - the other year to compare to, not null
        Returns:
        true if this is after the specified year
        Throws:
        NullPointerException - if other is null
      • isBefore

        public boolean isBefore​(Year other)
        Is this year before the specified year.
        Parameters:
        other - the other year to compare to, not null
        Returns:
        true if this point is before the specified year
        Throws:
        NullPointerException - if other is null
      • equals

        public boolean equals​(Object other)
        Is this year equal to the specified year.
        Overrides:
        equals in class Object
        Parameters:
        other - the other year to compare to, null returns false
        Returns:
        true if this point is equal to the specified year
      • hashCode

        public int hashCode()
        A hash code for this year.
        Overrides:
        hashCode in class Object
        Returns:
        a suitable hash code
      • toString

        public String toString()
        Outputs the string form of the year.
        Overrides:
        toString in class Object
        Returns:
        the string form of the year