Package org.joda.time

Class YearMonth

All Implemented Interfaces:
Serializable, Comparable<ReadablePartial>, ReadablePartial

public final class YearMonth extends BasePartial implements ReadablePartial, Serializable
YearMonth is an immutable partial supporting the year and monthOfYear fields.

NOTE: This class only supports the two fields listed above. It is impossible to query any other fields, such as dayOfWeek or centuryOfEra.

Calculations on YearMonth are performed using a Chronology. This chronology is set to be in the UTC time zone for all calculations.

One use case for this class is to store a credit card expiry date, as that only references the year and month. This class can be used as the gYearMonth type in XML Schema.

Each individual field can be queried in two ways:

  • getMonthOfYear()
  • monthOfYear().get()
The second technique also provides access to other useful methods on the field:
  • numeric value - monthOfYear().get()
  • text value - monthOfYear().getAsText()
  • short text value - monthOfYear().getAsShortText()
  • maximum/minimum values - monthOfYear().getMaximumValue()
  • add/subtract - monthOfYear().addToCopy()
  • set - monthOfYear().setCopy()

YearMonth is thread-safe and immutable, provided that the Chronology is as well. All standard Chronology classes supplied are thread-safe and immutable.

Since:
2.0
Author:
Stephen Colebourne
See Also:
  • Field Details

    • YEAR

      public static final int YEAR
      The index of the year field in the field array
      See Also:
    • MONTH_OF_YEAR

      public static final int MONTH_OF_YEAR
      The index of the monthOfYear field in the field array
      See Also:
  • Constructor Details

    • YearMonth

      public YearMonth()
      Constructs a YearMonth with the current year-month, using ISOChronology in the default zone to extract the fields.

      The constructor uses the default time zone, resulting in the local time being initialised. Once the constructor is complete, all further calculations are performed without reference to a time-zone (by switching to UTC).

      See Also:
    • YearMonth

      public YearMonth(DateTimeZone zone)
      Constructs a YearMonth with the current year-month, using ISOChronology in the specified zone to extract the fields.

      The constructor uses the specified time zone to obtain the current year-month. Once the constructor is complete, all further calculations are performed without reference to a time-zone (by switching to UTC).

      Parameters:
      zone - the zone to use, null means default zone
      See Also:
    • YearMonth

      public YearMonth(Chronology chronology)
      Constructs a YearMonth with the current year-month, using the specified chronology and zone to extract the fields.

      The constructor uses the time zone of the chronology specified. Once the constructor is complete, all further calculations are performed without reference to a time-zone (by switching to UTC).

      Parameters:
      chronology - the chronology, null means ISOChronology in the default zone
      See Also:
    • YearMonth

      public YearMonth(long instant)
      Constructs a YearMonth extracting the partial fields from the specified milliseconds using the ISOChronology in the default zone.

      The constructor uses the default time zone, resulting in the local time being initialised. Once the constructor is complete, all further calculations are performed without reference to a time-zone (by switching to UTC).

      Parameters:
      instant - the milliseconds from 1970-01-01T00:00:00Z
    • YearMonth

      public YearMonth(long instant, Chronology chronology)
      Constructs a YearMonth extracting the partial fields from the specified milliseconds using the chronology provided.

      The constructor uses the time zone of the chronology specified. Once the constructor is complete, all further calculations are performed without reference to a time-zone (by switching to UTC).

      Parameters:
      instant - the milliseconds from 1970-01-01T00:00:00Z
      chronology - the chronology, null means ISOChronology in the default zone
    • YearMonth

      public YearMonth(Object instant)
      Constructs a YearMonth from an Object that represents some form of time.

      The recognised object types are defined in ConverterManager and include ReadableInstant, String, Calendar and Date. The String formats are described by ISODateTimeFormat.localDateParser().

      The chronology used will be derived from the object, defaulting to ISO.

      Parameters:
      instant - the date-time object, null means now
      Throws:
      IllegalArgumentException - if the instant is invalid
    • YearMonth

      public YearMonth(Object instant, Chronology chronology)
      Constructs a YearMonth from an Object that represents some form of time, using the specified chronology.

      The recognised object types are defined in ConverterManager and include ReadableInstant, String, Calendar and Date. The String formats are described by ISODateTimeFormat.localDateParser().

      The constructor uses the time zone of the chronology specified. Once the constructor is complete, all further calculations are performed without reference to a time-zone (by switching to UTC). The specified chronology overrides that of the object.

      Parameters:
      instant - the date-time object, null means now
      chronology - the chronology, null means ISO default
      Throws:
      IllegalArgumentException - if the instant is invalid
    • YearMonth

      public YearMonth(int year, int monthOfYear)
      Constructs a YearMonth with specified year and month using ISOChronology.

      The constructor uses the no time zone initialising the fields as provided. Once the constructor is complete, all further calculations are performed without reference to a time-zone (by switching to UTC).

      Parameters:
      year - the year
      monthOfYear - the month of the year
    • YearMonth

      public YearMonth(int year, int monthOfYear, Chronology chronology)
      Constructs an instance set to the specified year and month using the specified chronology, whose zone is ignored.

      If the chronology is null, ISOChronology is used.

      The constructor uses the time zone of the chronology specified. Once the constructor is complete, all further calculations are performed without reference to a time-zone (by switching to UTC).

      Parameters:
      year - the year
      monthOfYear - the month of the year
      chronology - the chronology, null means ISOChronology in the default zone
  • Method Details

    • now

      public static YearMonth now()
      Obtains a YearMonth set to the current system millisecond time using ISOChronology in the default time zone. The resulting object does not use the zone.
      Returns:
      the current year-month, not null
      Since:
      2.0
    • now

      public static YearMonth now(DateTimeZone zone)
      Obtains a YearMonth set to the current system millisecond time using ISOChronology in the specified time zone. The resulting object does not use the zone.
      Parameters:
      zone - the time zone, not null
      Returns:
      the current year-month, not null
      Since:
      2.0
    • now

      public static YearMonth now(Chronology chronology)
      Obtains a YearMonth set to the current system millisecond time using the specified chronology. The resulting object does not use the zone.
      Parameters:
      chronology - the chronology, not null
      Returns:
      the current year-month, not null
      Since:
      2.0
    • parse

      public static YearMonth parse(String str)
      Parses a YearMonth from the specified string.

      This uses ISODateTimeFormat.localDateParser().

      Parameters:
      str - the string to parse, not null
      Returns:
      the parsed year-month, not null
      Since:
      2.0
    • parse

      public static YearMonth parse(String str, DateTimeFormatter formatter)
      Parses a YearMonth from the specified string using a formatter.
      Parameters:
      str - the string to parse, not null
      formatter - the formatter to use, not null
      Returns:
      the parsed year-month, not null
      Since:
      2.0
    • fromCalendarFields

      public static YearMonth fromCalendarFields(Calendar calendar)
      Constructs a YearMonth from a java.util.Calendar using exactly the same field values avoiding any time zone effects.

      Each field is queried from the Calendar and assigned to the YearMonth.

      This factory method ignores the type of the calendar and always creates a YearMonth with ISO chronology. It is expected that you will only pass in instances of GregorianCalendar however this is not validated.

      Parameters:
      calendar - the Calendar to extract fields from
      Returns:
      the created YearMonth, never null
      Throws:
      IllegalArgumentException - if the calendar is null
      IllegalArgumentException - if the year or month is invalid for the ISO chronology
    • fromDateFields

      public static YearMonth fromDateFields(Date date)
      Constructs a YearMonth from a java.util.Date using exactly the same field values avoiding any time zone effects.

      Each field is queried from the Date and assigned to the YearMonth.

      This factory method always creates a YearMonth with ISO chronology.

      Parameters:
      date - the Date to extract fields from
      Returns:
      the created YearMonth, never null
      Throws:
      IllegalArgumentException - if the calendar is null
      IllegalArgumentException - if the year or month is invalid for the ISO chronology
    • size

      public int size()
      Gets the number of fields in this partial, which is two. The supported fields are Year and MonthOfYear. Note that only these fields may be queried.
      Specified by:
      size in interface ReadablePartial
      Returns:
      the field count, two
    • getField

      protected DateTimeField getField(int index, Chronology chrono)
      Gets the field for a specific index in the chronology specified.

      This method must not use any instance variables.

      Specified by:
      getField in class AbstractPartial
      Parameters:
      index - the index to retrieve
      chrono - the chronology to use
      Returns:
      the field, never null
    • getFieldType

      public DateTimeFieldType getFieldType(int index)
      Gets the field type at the specified index.
      Specified by:
      getFieldType in interface ReadablePartial
      Overrides:
      getFieldType in class AbstractPartial
      Parameters:
      index - the index to retrieve
      Returns:
      the field at the specified index, never null
      Throws:
      IndexOutOfBoundsException - if the index is invalid
    • getFieldTypes

      public DateTimeFieldType[] getFieldTypes()
      Gets an array of the field type of each of the fields that this partial supports.

      The fields are returned largest to smallest, Year, Month.

      Overrides:
      getFieldTypes in class AbstractPartial
      Returns:
      the array of field types (cloned), largest to smallest, never null
    • withChronologyRetainFields

      public YearMonth withChronologyRetainFields(Chronology newChronology)
      Returns a copy of this year-month with the specified chronology. This instance is immutable and unaffected by this method call.

      This method retains the values of the fields, thus the result will typically refer to a different instant.

      The time zone of the specified chronology is ignored, as YearMonth operates without a time zone.

      Parameters:
      newChronology - the new chronology, null means ISO
      Returns:
      a copy of this year-month with a different chronology, never null
      Throws:
      IllegalArgumentException - if the values are invalid for the new chronology
    • withField

      public YearMonth withField(DateTimeFieldType fieldType, int value)
      Returns a copy of this year-month with the specified field set to a new value.

      For example, if the field type is monthOfYear then the month would be changed in the returned instance.

      These three lines are equivalent:

       YearMonth updated = ym.withField(DateTimeFieldType.monthOfYear(), 6);
       YearMonth updated = ym.monthOfYear().setCopy(6);
       YearMonth updated = ym.property(DateTimeFieldType.monthOfYear()).setCopy(6);
       
      Parameters:
      fieldType - the field type to set, not null
      value - the value to set
      Returns:
      a copy of this instance with the field set, never null
      Throws:
      IllegalArgumentException - if the value is null or invalid
    • withFieldAdded

      public YearMonth withFieldAdded(DurationFieldType fieldType, int amount)
      Returns a copy of this year-month with the value of the specified field increased.

      If the addition is zero, then this is returned.

      These three lines are equivalent:

       YearMonth added = ym.withFieldAdded(DurationFieldType.months(), 6);
       YearMonth added = ym.plusMonths(6);
       YearMonth added = ym.monthOfYear().addToCopy(6);
       
      Parameters:
      fieldType - the field type to add to, not null
      amount - the amount to add
      Returns:
      a copy of this instance with the field updated, never null
      Throws:
      IllegalArgumentException - if the value is null or invalid
      ArithmeticException - if the new date-time exceeds the capacity
    • withPeriodAdded

      public YearMonth withPeriodAdded(ReadablePeriod period, int scalar)
      Returns a copy of this year-month with the specified period added.

      If the addition is zero, then this is returned. Fields in the period that aren't present in the partial are ignored.

      This method is typically used to add multiple copies of complex period instances. Adding one field is best achieved using methods like withFieldAdded(DurationFieldType, int) or plusYears(int).

      Parameters:
      period - the period to add to this one, null means zero
      scalar - the amount of times to add, such as -1 to subtract once
      Returns:
      a copy of this instance with the period added, never null
      Throws:
      ArithmeticException - if the new date-time exceeds the capacity
    • plus

      public YearMonth plus(ReadablePeriod period)
      Returns a copy of this year-month with the specified period added.

      If the amount is zero or null, then this is returned.

      This method is typically used to add complex period instances. Adding one field is best achieved using methods like plusYears(int).

      Parameters:
      period - the duration to add to this one, null means zero
      Returns:
      a copy of this instance with the period added, never null
      Throws:
      ArithmeticException - if the new year-month exceeds the capacity
    • plusYears

      public YearMonth plusYears(int years)
      Returns a copy of this year-month plus the specified number of years.

      This year-month instance is immutable and unaffected by this method call.

      The following three lines are identical in effect:

       YearMonth added = ym.plusYears(6);
       YearMonth added = ym.plus(Period.years(6));
       YearMonth added = ym.withFieldAdded(DurationFieldType.years(), 6);
       
      Parameters:
      years - the amount of years to add, may be negative
      Returns:
      the new year-month plus the increased years, never null
    • plusMonths

      public YearMonth plusMonths(int months)
      Returns a copy of this year-month plus the specified number of months.

      This year-month instance is immutable and unaffected by this method call.

      The following three lines are identical in effect:

       YearMonth added = ym.plusMonths(6);
       YearMonth added = ym.plus(Period.months(6));
       YearMonth added = ym.withFieldAdded(DurationFieldType.months(), 6);
       
      Parameters:
      months - the amount of months to add, may be negative
      Returns:
      the new year-month plus the increased months, never null
    • minus

      public YearMonth minus(ReadablePeriod period)
      Returns a copy of this year-month with the specified period taken away.

      If the amount is zero or null, then this is returned.

      This method is typically used to subtract complex period instances. Subtracting one field is best achieved using methods like minusYears(int).

      Parameters:
      period - the period to reduce this instant by
      Returns:
      a copy of this instance with the period taken away, never null
      Throws:
      ArithmeticException - if the new year-month exceeds the capacity
    • minusYears

      public YearMonth minusYears(int years)
      Returns a copy of this year-month minus the specified number of years.

      This year-month instance is immutable and unaffected by this method call.

      The following three lines are identical in effect:

       YearMonth subtracted = ym.minusYears(6);
       YearMonth subtracted = ym.minus(Period.years(6));
       YearMonth subtracted = ym.withFieldAdded(DurationFieldType.years(), -6);
       
      Parameters:
      years - the amount of years to subtract, may be negative
      Returns:
      the new year-month minus the increased years, never null
    • minusMonths

      public YearMonth minusMonths(int months)
      Returns a copy of this year-month minus the specified number of months.

      This year-month instance is immutable and unaffected by this method call.

      The following three lines are identical in effect:

       YearMonth subtracted = ym.minusMonths(6);
       YearMonth subtracted = ym.minus(Period.months(6));
       YearMonth subtracted = ym.withFieldAdded(DurationFieldType.months(), -6);
       
      Parameters:
      months - the amount of months to subtract, may be negative
      Returns:
      the new year-month minus the increased months, never null
    • toLocalDate

      public LocalDate toLocalDate(int dayOfMonth)
      Converts this object to a LocalDate with the same year-month and chronology.
      Parameters:
      dayOfMonth - the day of month to use, valid for chronology, such as 1-31 for ISO
      Returns:
      a LocalDate with the same year-month and chronology, never null
    • toInterval

      public Interval toInterval()
      Converts this object to an Interval representing the whole month.

      The interval will use the chronology of the year-month in the default zone.

      This instance is immutable and unaffected by this method call.

      Returns:
      an interval over the month, never null
    • toInterval

      public Interval toInterval(DateTimeZone zone)
      Converts this object to an Interval representing the whole month.

      The interval will use the chronology of the year-month in the specified zone.

      This instance is immutable and unaffected by this method call.

      Parameters:
      zone - the zone to get the Interval in, null means default
      Returns:
      an interval over the month, never null
    • getYear

      public int getYear()
      Get the year field value.
      Returns:
      the year
    • getMonthOfYear

      public int getMonthOfYear()
      Get the month of year field value.
      Returns:
      the month of year
    • withYear

      public YearMonth withYear(int year)
      Returns a copy of this year-month with the year field updated.

      YearMonth is immutable, so there are no set methods. Instead, this method returns a new instance with the value of year changed.

      Parameters:
      year - the year to set
      Returns:
      a copy of this object with the field set, never null
      Throws:
      IllegalArgumentException - if the value is invalid
    • withMonthOfYear

      public YearMonth withMonthOfYear(int monthOfYear)
      Returns a copy of this year-month with the month of year field updated.

      YearMonth is immutable, so there are no set methods. Instead, this method returns a new instance with the value of month of year changed.

      Parameters:
      monthOfYear - the month of year to set
      Returns:
      a copy of this object with the field set, never null
      Throws:
      IllegalArgumentException - if the value is invalid
    • property

      public YearMonth.Property property(DateTimeFieldType type)
      Gets the property object for the specified type, which contains many useful methods.
      Parameters:
      type - the field type to get the property for
      Returns:
      the property object
      Throws:
      IllegalArgumentException - if the field is null or unsupported
    • year

      public YearMonth.Property year()
      Get the year field property which provides access to advanced functionality.
      Returns:
      the year property
    • monthOfYear

      public YearMonth.Property monthOfYear()
      Get the month of year field property which provides access to advanced functionality.
      Returns:
      the month of year property
    • toString

      public String toString()
      Output the year-month in ISO8601 format (yyyy-MM).
      Specified by:
      toString in interface ReadablePartial
      Overrides:
      toString in class Object
      Returns:
      ISO8601 time formatted string.
    • toString

      public String toString(String pattern)
      Output the year-month using the specified format pattern.
      Overrides:
      toString in class BasePartial
      Parameters:
      pattern - the pattern specification, null means use toString
      Returns:
      the formatted output, not null
      See Also:
    • toString

      public String toString(String pattern, Locale locale) throws IllegalArgumentException
      Output the year-month using the specified format pattern.
      Overrides:
      toString in class BasePartial
      Parameters:
      pattern - the pattern specification, null means use toString
      locale - Locale to use, null means default
      Returns:
      the formatted output, not null
      Throws:
      IllegalArgumentException - if the pattern is invalid
      See Also: