Module java.base
Package java.time

Class YearMonth

java.lang.Object
java.time.YearMonth
All Implemented Interfaces:
Serializable, Comparable<YearMonth>, Temporal, TemporalAccessor, TemporalAdjuster
public final class YearMonth extends Object implements Temporal, TemporalAdjuster, Comparable<YearMonth>, Serializable
A year-month in the ISO-8601 calendar system, such as 2007-12.

YearMonth is an immutable date-time object that represents the combination of a year and month. Any field that can be derived from a year and month, such as quarter-of-year, can be obtained.

This class does not store or represent a day, time or time-zone. For example, the value "October 2007" can be stored in a YearMonth.

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 today's rules for leap years are applied for all time. For most applications written today, the ISO-8601 rules are entirely suitable. However, any application that makes use of historical dates, and requires them to be accurate will find the ISO-8601 approach unsuitable.

This is a value-based class; programmers should treat instances that are equal as interchangeable and should not use instances for synchronization, or unpredictable behavior may occur. For example, in a future release, synchronization may fail. 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
    Temporal
    adjustInto​(Temporal temporal)
    Adjusts the specified temporal object to have this year-month.
    LocalDate
    atDay​(int dayOfMonth)
    Combines this year-month with a day-of-month to create a LocalDate.
    LocalDate
    atEndOfMonth()
    Returns a LocalDate at the end of the month.
    int
    compareTo​(YearMonth other)
    Compares this year-month to another year-month.
    boolean
    equals​(Object obj)
    Checks if this year-month is equal to another year-month.
    String
    format​(DateTimeFormatter formatter)
    Formats this year-month using the specified formatter.
    static YearMonth
    from​(TemporalAccessor temporal)
    Obtains an instance of YearMonth from a temporal object.
    int
    get​(TemporalField field)
    Gets the value of the specified field from this year-month as an int.
    long
    getLong​(TemporalField field)
    Gets the value of the specified field from this year-month as a long.
    Month
    getMonth()
    Gets the month-of-year field using the Month enum.
    int
    getMonthValue()
    Gets the month-of-year field from 1 to 12.
    int
    getYear()
    Gets the year field.
    int
    hashCode()
    A hash code for this year-month.
    boolean
    isAfter​(YearMonth other)
    Checks if this year-month is after the specified year-month.
    boolean
    isBefore​(YearMonth other)
    Checks if this year-month is before the specified year-month.
    boolean
    isLeapYear()
    Checks if the year is a leap year, according to the ISO proleptic calendar system rules.
    boolean
    isSupported​(TemporalField field)
    Checks if the specified field is supported.
    boolean
    isSupported​(TemporalUnit unit)
    Checks if the specified unit is supported.
    boolean
    isValidDay​(int dayOfMonth)
    Checks if the day-of-month is valid for this year-month.
    int
    lengthOfMonth()
    Returns the length of the month, taking account of the year.
    int
    lengthOfYear()
    Returns the length of the year.
    YearMonth
    minus​(long amountToSubtract, TemporalUnit unit)
    Returns a copy of this year-month with the specified amount subtracted.
    YearMonth
    minus​(TemporalAmount amountToSubtract)
    Returns a copy of this year-month with the specified amount subtracted.
    YearMonth
    minusMonths​(long monthsToSubtract)
    Returns a copy of this YearMonth with the specified number of months subtracted.
    YearMonth
    minusYears​(long yearsToSubtract)
    Returns a copy of this YearMonth with the specified number of years subtracted.
    static YearMonth
    now()
    Obtains the current year-month from the system clock in the default time-zone.
    static YearMonth
    now​(Clock clock)
    Obtains the current year-month from the specified clock.
    static YearMonth
    now​(ZoneId zone)
    Obtains the current year-month from the system clock in the specified time-zone.
    static YearMonth
    of​(int year, int month)
    Obtains an instance of YearMonth from a year and month.
    static YearMonth
    of​(int year, Month month)
    Obtains an instance of YearMonth from a year and month.
    static YearMonth
    parse​(CharSequence text)
    Obtains an instance of YearMonth from a text string such as 2007-12.
    static YearMonth
    parse​(CharSequence text, DateTimeFormatter formatter)
    Obtains an instance of YearMonth from a text string using a specific formatter.
    YearMonth
    plus​(long amountToAdd, TemporalUnit unit)
    Returns a copy of this year-month with the specified amount added.
    YearMonth
    plus​(TemporalAmount amountToAdd)
    Returns a copy of this year-month with the specified amount added.
    YearMonth
    plusMonths​(long monthsToAdd)
    Returns a copy of this YearMonth with the specified number of months added.
    YearMonth
    plusYears​(long yearsToAdd)
    Returns a copy of this YearMonth with the specified number of years added.
    <R> R
    query​(TemporalQuery<R> query)
    Queries this year-month using the specified query.
    ValueRange
    range​(TemporalField field)
    Gets the range of valid values for the specified field.
    String
    toString()
    Outputs this year-month as a String, such as 2007-12.
    long
    until​(Temporal endExclusive, TemporalUnit unit)
    Calculates the amount of time until another year-month in terms of the specified unit.
    YearMonth
    with​(TemporalAdjuster adjuster)
    Returns an adjusted copy of this year-month.
    YearMonth
    with​(TemporalField field, long newValue)
    Returns a copy of this year-month with the specified field set to a new value.
    YearMonth
    withMonth​(int month)
    Returns a copy of this YearMonth with the month-of-year altered.
    YearMonth
    withYear​(int year)
    Returns a copy of this YearMonth with the year altered.

    Methods declared in class java.lang.Object

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

  • Method Details

    • now

      public static YearMonth now()
      Obtains the current year-month 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-month.

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

      Returns:
      the current year-month using the system clock and default time-zone, not null

    • now

      public static YearMonth now​(ZoneId zone)
      Obtains the current year-month from the system clock in the specified time-zone.

      This will query the system clock to obtain the current year-month. 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 year-month using the system clock, not null

    • now

      public static YearMonth now​(Clock clock)
      Obtains the current year-month from the specified clock.

      This will query the specified clock to obtain the current year-month. 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-month, not null

    • of

      public static YearMonth of​(int year, Month month)
      Obtains an instance of YearMonth from a year and month.
      Parameters:
      year - the year to represent, from MIN_YEAR to MAX_YEAR
      month - the month-of-year to represent, not null
      Returns:
      the year-month, not null
      Throws:
      DateTimeException - if the year value is invalid

    • of

      public static YearMonth of​(int year, int month)
      Obtains an instance of YearMonth from a year and month.
      Parameters:
      year - the year to represent, from MIN_YEAR to MAX_YEAR
      month - the month-of-year to represent, from 1 (January) to 12 (December)
      Returns:
      the year-month, not null
      Throws:
      DateTimeException - if either field value is invalid

    • from

      public static YearMonth from​(TemporalAccessor temporal)
      Obtains an instance of YearMonth from a temporal object.

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

      The conversion extracts the YEAR and MONTH_OF_YEAR fields. The extraction is only permitted if the temporal object has an ISO chronology, or can be converted to a LocalDate.

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

      Parameters:
      temporal - the temporal object to convert, not null
      Returns:
      the year-month, not null
      Throws:
      DateTimeException - if unable to convert to a YearMonth

    • parse

      public static YearMonth parse​(CharSequence text)
      Obtains an instance of YearMonth from a text string such as 2007-12.

      The string must represent a valid year-month. The format must be uuuu-MM. Years outside the range 0000 to 9999 must be prefixed by the plus or minus symbol.

      Parameters:
      text - the text to parse such as "2007-12", not null
      Returns:
      the parsed year-month, not null
      Throws:
      DateTimeParseException - if the text cannot be parsed

    • parse

      public static YearMonth parse​(CharSequence text, DateTimeFormatter formatter)
      Obtains an instance of YearMonth from a text string using a specific formatter.

      The text is parsed using the formatter, returning a year-month.

      Parameters:
      text - the text to parse, not null
      formatter - the formatter to use, not null
      Returns:
      the parsed year-month, not null
      Throws:
      DateTimeParseException - if the text cannot be parsed

    • isSupported

      public boolean isSupported​(TemporalField field)
      Checks if the specified field is supported.

      This checks if this year-month can be queried for the specified field. If false, then calling the range, get and with(TemporalField, long) methods will throw an exception.

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

      • 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 TemporalAccessor
      Parameters:
      field - the field to check, null returns false
      Returns:
      true if the field is supported on this year-month, false if not

    • isSupported

      public boolean isSupported​(TemporalUnit unit)
      Checks if the specified unit is supported.

      This checks if the specified unit can be added to, or subtracted from, this year-month. If false, then calling the plus(long, TemporalUnit) and minus methods will throw an exception.

      If the unit is a ChronoUnit then the query is implemented here. The supported units are:

      • MONTHS
      • YEARS
      • DECADES
      • CENTURIES
      • MILLENNIA
      • ERAS
      All other ChronoUnit instances will return false.

      If the unit is not a ChronoUnit, then the result of this method is obtained by invoking TemporalUnit.isSupportedBy(Temporal) passing this as the argument. Whether the unit is supported is determined by the unit.

      Specified by:
      isSupported in interface Temporal
      Parameters:
      unit - the unit to check, null returns false
      Returns:
      true if the unit can be added/subtracted, false if not

    • range

      public ValueRange range​(TemporalField field)
      Gets the range of valid values for the specified field.

      The range object expresses the minimum and maximum valid values for a field. This year-month is used to enhance the accuracy of the returned range. If it is not possible to return the range, because the field is not supported or for some other reason, an exception is thrown.

      If the field is a ChronoField then the query is implemented here. The supported fields will return appropriate range instances. All other ChronoField instances will throw an UnsupportedTemporalTypeException.

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

      Specified by:
      range in interface TemporalAccessor
      Parameters:
      field - the field to query the range for, not null
      Returns:
      the range of valid values for the field, not null
      Throws:
      DateTimeException - if the range for the field cannot be obtained
      UnsupportedTemporalTypeException - if the field is not supported

    • get

      public int get​(TemporalField field)
      Gets the value of the specified field from this year-month as an int.

      This queries this year-month for the value of the specified field. The returned value will always be within the valid range of values for the field. If it is not possible to return the value, because the field is not supported or for some other reason, an exception is thrown.

      If the field is a ChronoField then the query is implemented here. The supported fields will return valid values based on this year-month, except PROLEPTIC_MONTH which is too large to fit in an int and throw a DateTimeException. All other ChronoField instances will throw an UnsupportedTemporalTypeException.

      If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.getFrom(TemporalAccessor) passing this as the argument. Whether the value can be obtained, and what the value represents, is determined by the field.

      Specified by:
      get in interface TemporalAccessor
      Parameters:
      field - the field to get, not null
      Returns:
      the value for the field
      Throws:
      DateTimeException - if a value for the field cannot be obtained or the value is outside the range of valid values for the field
      UnsupportedTemporalTypeException - if the field is not supported or the range of values exceeds an int
      ArithmeticException - if numeric overflow occurs

    • getLong

      public long getLong​(TemporalField field)
      Gets the value of the specified field from this year-month as a long.

      This queries this year-month for the value of the specified field. If it is not possible to return the value, because the field is not supported or for some other reason, an exception is thrown.

      If the field is a ChronoField then the query is implemented here. The supported fields will return valid values based on this year-month. All other ChronoField instances will throw an UnsupportedTemporalTypeException.

      If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.getFrom(TemporalAccessor) passing this as the argument. Whether the value can be obtained, and what the value represents, is determined by the field.

      Specified by:
      getLong in interface TemporalAccessor
      Parameters:
      field - the field to get, not null
      Returns:
      the value for the field
      Throws:
      DateTimeException - if a value for the field cannot be obtained
      UnsupportedTemporalTypeException - if the field is not supported
      ArithmeticException - if numeric overflow occurs

    • getYear

      public int getYear()
      Gets the year field.

      This method returns the primitive int value for the year.

      The year returned by this method is proleptic as per get(YEAR).

      Returns:
      the year, from MIN_YEAR to MAX_YEAR

    • getMonthValue

      public int getMonthValue()
      Gets the month-of-year field from 1 to 12.

      This method returns the month as an int from 1 to 12. Application code is frequently clearer if the enum Month is used by calling getMonth().

      Returns:
      the month-of-year, from 1 to 12
      See Also:
      getMonth()

    • getMonth

      public Month getMonth()
      Gets the month-of-year field using the Month enum.

      This method returns the enum Month for the month. This avoids confusion as to what int values mean. If you need access to the primitive int value then the enum provides the int value.

      Returns:
      the month-of-year, not null
      See Also:
      getMonthValue()

    • isLeapYear

      public boolean isLeapYear()
      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 ISO-8601 standard.

      Returns:
      true if the year is leap, false otherwise

    • isValidDay

      public boolean isValidDay​(int dayOfMonth)
      Checks if the day-of-month is valid for this year-month.

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

      Parameters:
      dayOfMonth - the day-of-month to validate, from 1 to 31, invalid value returns false
      Returns:
      true if the day is valid for this year-month

    • lengthOfMonth

      public int lengthOfMonth()
      Returns the length of the month, taking account of the year.

      This returns the length of the month in days. For example, a date in January would return 31.

      Returns:
      the length of the month in days, from 28 to 31

    • lengthOfYear

      public int lengthOfYear()
      Returns the length of the year.

      This returns the length of the year in days, either 365 or 366.

      Returns:
      366 if the year is leap, 365 otherwise

    • with

      public YearMonth with​(TemporalAdjuster adjuster)
      Returns an adjusted copy of this year-month.

      This returns a YearMonth, based on this one, with the year-month adjusted. The adjustment takes place using the specified adjuster strategy object. Read the documentation of the adjuster to understand what adjustment will be made.

      A simple adjuster might simply set the one of the fields, such as the year field. A more complex adjuster might set the year-month to the next month that Halley's comet will pass the Earth.

      The result of this method is obtained by invoking the TemporalAdjuster.adjustInto(Temporal) method on the specified adjuster passing this as the argument.

      This instance is immutable and unaffected by this method call.

      Specified by:
      with in interface Temporal
      Parameters:
      adjuster - the adjuster to use, not null
      Returns:
      a YearMonth based on this with the adjustment made, not null
      Throws:
      DateTimeException - if the adjustment cannot be made
      ArithmeticException - if numeric overflow occurs

    • with

      public YearMonth with​(TemporalField field, long newValue)
      Returns a copy of this year-month with the specified field set to a new value.

      This returns a YearMonth, based on this one, with the value for the specified field changed. This can be used to change any supported field, such as the year or month. If it is not possible to set the value, because the field is not supported or for some other reason, an exception is thrown.

      If the field is a ChronoField then the adjustment is implemented here. The supported fields behave as follows:

      • MONTH_OF_YEAR - Returns a YearMonth with the specified month-of-year. The year will be unchanged.
      • PROLEPTIC_MONTH - Returns a YearMonth with the specified proleptic-month. This completely replaces the year and month of this object.
      • YEAR_OF_ERA - Returns a YearMonth with the specified year-of-era The month and era will be unchanged.
      • YEAR - Returns a YearMonth with the specified year. The month will be unchanged.
      • ERA - Returns a YearMonth with the specified era. The month and year-of-era will be unchanged.

      In all cases, if the new value is outside the valid range of values for the field then a DateTimeException will be thrown.

      All other ChronoField instances will throw an UnsupportedTemporalTypeException.

      If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.adjustInto(Temporal, long) passing this as the argument. In this case, the field determines whether and how to adjust the instant.

      This instance is immutable and unaffected by this method call.

      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:
      a YearMonth based on this with the specified field set, not null
      Throws:
      DateTimeException - if the field cannot be set
      UnsupportedTemporalTypeException - if the field is not supported
      ArithmeticException - if numeric overflow occurs

    • withYear

      public YearMonth withYear​(int year)
      Returns a copy of this YearMonth with the year altered.

      This instance is immutable and unaffected by this method call.

      Parameters:
      year - the year to set in the returned year-month, from MIN_YEAR to MAX_YEAR
      Returns:
      a YearMonth based on this year-month with the requested year, not null
      Throws:
      DateTimeException - if the year value is invalid

    • withMonth

      public YearMonth withMonth​(int month)
      Returns a copy of this YearMonth with the month-of-year altered.

      This instance is immutable and unaffected by this method call.

      Parameters:
      month - the month-of-year to set in the returned year-month, from 1 (January) to 12 (December)
      Returns:
      a YearMonth based on this year-month with the requested month, not null
      Throws:
      DateTimeException - if the month-of-year value is invalid

    • plus

      public YearMonth plus​(TemporalAmount amountToAdd)
      Returns a copy of this year-month with the specified amount added.

      This returns a YearMonth, based on this one, with the specified amount added. The amount is typically Period but may be any other type implementing the TemporalAmount interface.

      The calculation is delegated to the amount object by calling TemporalAmount.addTo(Temporal). The amount implementation is free to implement the addition in any way it wishes, however it typically calls back to plus(long, TemporalUnit). Consult the documentation of the amount implementation to determine if it can be successfully added.

      This instance is immutable and unaffected by this method call.

      Specified by:
      plus in interface Temporal
      Parameters:
      amountToAdd - the amount to add, not null
      Returns:
      a YearMonth based on this year-month with the addition made, not null
      Throws:
      DateTimeException - if the addition cannot be made
      ArithmeticException - if numeric overflow occurs

    • plus

      public YearMonth plus​(long amountToAdd, TemporalUnit unit)
      Returns a copy of this year-month with the specified amount added.

      This returns a YearMonth, based on this one, with the amount in terms of the unit added. If it is not possible to add the amount, because the unit is not supported or for some other reason, an exception is thrown.

      If the field is a ChronoUnit then the addition is implemented here. The supported fields behave as follows:

      • MONTHS - Returns a YearMonth with the specified number of months added. This is equivalent to plusMonths(long).
      • YEARS - Returns a YearMonth with the specified number of years added. This is equivalent to plusYears(long).
      • DECADES - Returns a YearMonth with the specified number of decades added. This is equivalent to calling plusYears(long) with the amount multiplied by 10.
      • CENTURIES - Returns a YearMonth with the specified number of centuries added. This is equivalent to calling plusYears(long) with the amount multiplied by 100.
      • MILLENNIA - Returns a YearMonth with the specified number of millennia added. This is equivalent to calling plusYears(long) with the amount multiplied by 1,000.
      • ERAS - Returns a YearMonth with the specified number of eras added. Only two eras are supported so the amount must be one, zero or minus one. If the amount is non-zero then the year is changed such that the year-of-era is unchanged.

      All other ChronoUnit instances will throw an UnsupportedTemporalTypeException.

      If the field is not a ChronoUnit, then the result of this method is obtained by invoking TemporalUnit.addTo(Temporal, long) passing this as the argument. In this case, the unit determines whether and how to perform the addition.

      This instance is immutable and unaffected by this method call.

      Specified by:
      plus in interface Temporal
      Parameters:
      amountToAdd - the amount of the unit to add to the result, may be negative
      unit - the unit of the amount to add, not null
      Returns:
      a YearMonth based on this year-month with the specified amount added, not null
      Throws:
      DateTimeException - if the addition cannot be made
      UnsupportedTemporalTypeException - if the unit is not supported
      ArithmeticException - if numeric overflow occurs

    • plusYears

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

      This instance is immutable and unaffected by this method call.

      Parameters:
      yearsToAdd - the years to add, may be negative
      Returns:
      a YearMonth based on this year-month with the years added, not null
      Throws:
      DateTimeException - if the result exceeds the supported range

    • plusMonths

      public YearMonth plusMonths​(long monthsToAdd)
      Returns a copy of this YearMonth with the specified number of months added.

      This instance is immutable and unaffected by this method call.

      Parameters:
      monthsToAdd - the months to add, may be negative
      Returns:
      a YearMonth based on this year-month with the months added, not null
      Throws:
      DateTimeException - if the result exceeds the supported range

    • minus

      public YearMonth minus​(TemporalAmount amountToSubtract)
      Returns a copy of this year-month with the specified amount subtracted.

      This returns a YearMonth, based on this one, with the specified amount subtracted. The amount is typically Period but may be any other type implementing the TemporalAmount interface.

      The calculation is delegated to the amount object by calling TemporalAmount.subtractFrom(Temporal). The amount implementation is free to implement the subtraction in any way it wishes, however it typically calls back to minus(long, TemporalUnit). Consult the documentation of the amount implementation to determine if it can be successfully subtracted.

      This instance is immutable and unaffected by this method call.

      Specified by:
      minus in interface Temporal
      Parameters:
      amountToSubtract - the amount to subtract, not null
      Returns:
      a YearMonth based on this year-month with the subtraction made, not null
      Throws:
      DateTimeException - if the subtraction cannot be made
      ArithmeticException - if numeric overflow occurs

    • minus

      public YearMonth minus​(long amountToSubtract, TemporalUnit unit)
      Returns a copy of this year-month with the specified amount subtracted.

      This returns a YearMonth, based on this one, with the amount in terms of the unit subtracted. If it is not possible to subtract the amount, because the unit is not supported or for some other reason, an exception is thrown.

      This method is equivalent to plus(long, TemporalUnit) with the amount negated. See that method for a full description of how addition, and thus subtraction, works.

      This instance is immutable and unaffected by this method call.

      Specified by:
      minus in interface Temporal
      Parameters:
      amountToSubtract - the amount of the unit to subtract from the result, may be negative
      unit - the unit of the amount to subtract, not null
      Returns:
      a YearMonth based on this year-month with the specified amount subtracted, not null
      Throws:
      DateTimeException - if the subtraction cannot be made
      UnsupportedTemporalTypeException - if the unit is not supported
      ArithmeticException - if numeric overflow occurs

    • minusYears

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

      This instance is immutable and unaffected by this method call.

      Parameters:
      yearsToSubtract - the years to subtract, may be negative
      Returns:
      a YearMonth based on this year-month with the years subtracted, not null
      Throws:
      DateTimeException - if the result exceeds the supported range

    • minusMonths

      public YearMonth minusMonths​(long monthsToSubtract)
      Returns a copy of this YearMonth with the specified number of months subtracted.

      This instance is immutable and unaffected by this method call.

      Parameters:
      monthsToSubtract - the months to subtract, may be negative
      Returns:
      a YearMonth based on this year-month with the months subtracted, not null
      Throws:
      DateTimeException - if the result exceeds the supported range

    • query

      public <R> R query​(TemporalQuery<R> query)
      Queries this year-month using the specified query.

      This queries this year-month using the specified query strategy object. The TemporalQuery object defines the logic to be used to obtain the result. Read the documentation of the query to understand what the result of this method will be.

      The result of this method is obtained by invoking the TemporalQuery.queryFrom(TemporalAccessor) method on the specified query passing this as the argument.

      Specified by:
      query in interface TemporalAccessor
      Type Parameters:
      R - the type of the result
      Parameters:
      query - the query to invoke, not null
      Returns:
      the query result, null may be returned (defined by the query)
      Throws:
      DateTimeException - if unable to query (defined by the query)
      ArithmeticException - if numeric overflow occurs (defined by the query)

    • adjustInto

      public Temporal adjustInto​(Temporal temporal)
      Adjusts the specified temporal object to have this year-month.

      This returns a temporal object of the same observable type as the input with the year and month changed to be the same as this.

      The adjustment is equivalent to using Temporal.with(TemporalField, long) passing ChronoField.PROLEPTIC_MONTH as the field. If the specified temporal object does not use the ISO calendar system then a DateTimeException is thrown.

      In most cases, it is clearer to reverse the calling pattern by using Temporal.with(TemporalAdjuster): 

         // these two lines are equivalent, but the second approach is recommended
   temporal = thisYearMonth.adjustInto(temporal);
   temporal = temporal.with(thisYearMonth);

      This instance is immutable and unaffected by this method call.

      Specified by:
      adjustInto in interface TemporalAdjuster
      Parameters:
      temporal - the target object to be adjusted, not null
      Returns:
      the adjusted object, not null
      Throws:
      DateTimeException - if unable to make the adjustment
      ArithmeticException - if numeric overflow occurs

    • until

      public long until​(Temporal endExclusive, TemporalUnit unit)
      Calculates the amount of time until another year-month in terms of the specified unit.

      This calculates the amount of time between two YearMonth objects in terms of a single TemporalUnit. The start and end points are this and the specified year-month. The result will be negative if the end is before the start. The Temporal passed to this method is converted to a YearMonth using from(TemporalAccessor). For example, the amount in years between two year-months can be calculated using startYearMonth.until(endYearMonth, YEARS).

      The calculation returns a whole number, representing the number of complete units between the two year-months. For example, the amount in decades between 2012-06 and 2032-05 will only be one decade as it is one month short of two decades.

      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 MONTHS, YEARS, DECADES, CENTURIES, MILLENNIA and ERAS are supported. 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 Temporal
      Parameters:
      endExclusive - the end date, exclusive, which is converted to a YearMonth, not null
      unit - the unit to measure the amount in, not null
      Returns:
      the amount of time between this year-month and the end year-month
      Throws:
      DateTimeException - if the amount cannot be calculated, or the end temporal cannot be converted to a YearMonth
      UnsupportedTemporalTypeException - if the unit is not supported
      ArithmeticException - if numeric overflow occurs

    • format

      public String format​(DateTimeFormatter formatter)
      Formats this year-month using the specified formatter.

      This year-month will be passed to the formatter to produce a string.

      Parameters:
      formatter - the formatter to use, not null
      Returns:
      the formatted year-month string, not null
      Throws:
      DateTimeException - if an error occurs during printing

    • atDay

      public LocalDate atDay​(int dayOfMonth)
      Combines this year-month with a day-of-month to create a LocalDate.

      This returns a LocalDate formed from this year-month and the specified day-of-month.

      The day-of-month value must be valid for the year-month.

      This method can be used as part of a chain to produce a date: 

        LocalDate date = year.atMonth(month).atDay(day);
      Parameters:
      dayOfMonth - the day-of-month to use, from 1 to 31
      Returns:
      the date formed from this year-month and the specified day, not null
      Throws:
      DateTimeException - if the day is invalid for the year-month
      See Also:
      isValidDay(int)

    • atEndOfMonth

      public LocalDate atEndOfMonth()
      Returns a LocalDate at the end of the month.

      This returns a LocalDate based on this year-month. The day-of-month is set to the last valid day of the month, taking into account leap years.

      This method can be used as part of a chain to produce a date: 

        LocalDate date = year.atMonth(month).atEndOfMonth();
      Returns:
      the last valid date of this year-month, not null

    • compareTo

      public int compareTo​(YearMonth other)
      Compares this year-month to another year-month.

      The comparison is based first on the value of the year, then on the value of the month. It is "consistent with equals", as defined by Comparable.

      Specified by:
      compareTo in interface Comparable<YearMonth>
      Parameters:
      other - the other year-month to compare to, not null
      Returns:
      the comparator value, negative if less, positive if greater

    • isAfter

      public boolean isAfter​(YearMonth other)
      Checks if this year-month is after the specified year-month.
      Parameters:
      other - the other year-month to compare to, not null
      Returns:
      true if this is after the specified year-month

    • isBefore

      public boolean isBefore​(YearMonth other)
      Checks if this year-month is before the specified year-month.
      Parameters:
      other - the other year-month to compare to, not null
      Returns:
      true if this point is before the specified year-month

    • equals

      public boolean equals​(Object obj)
      Checks if this year-month is equal to another year-month.

      The comparison is based on the time-line position of the year-months.

      Overrides:
      equals in class Object
      Parameters:
      obj - the object to check, null returns false
      Returns:
      true if this is equal to the other year-month
      See Also:
      Object.hashCode(), HashMap

    • hashCode

      public int hashCode()
      A hash code for this year-month.
      Overrides:
      hashCode in class Object
      Returns:
      a suitable hash code
      See Also:
      Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

    • toString

      public String toString()
      Outputs this year-month as a String, such as 2007-12.

      The output will be in the format uuuu-MM:

      Overrides:
      toString in class Object
      Returns:
      a string representation of this year-month, not null