org.joda.time
Class YearMonth

java.lang.Object
  org.joda.time.base.AbstractPartial
      org.joda.time.base.BasePartial
          org.joda.time.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:

Serialized Form

Nested Class Summary

static class

YearMonth.Property The property class for YearMonth.

Field Summary

static int	MONTH_OF_YEAR The index of the monthOfYear field in the field array
static int	YEAR The index of the year field in the field array

Constructor Summary

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

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

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

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

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.

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

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

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

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

Method Summary

static YearMonth	fromCalendarFields(Calendar calendar) Constructs a YearMonth from a java.util.Calendar using exactly the same field values avoiding any time zone effects.
static YearMonth	fromDateFields(Date date) Constructs a YearMonth from a java.util.Date using exactly the same field values avoiding any time zone effects.
protected DateTimeField	getField(int index, Chronology chrono) Gets the field for a specific index in the chronology specified.
DateTimeFieldType	getFieldType(int index) Gets the field type at the specified index.
DateTimeFieldType[]	getFieldTypes() Gets an array of the field type of each of the fields that this partial supports.
int	getMonthOfYear() Get the month of year field value.
int	getYear() Get the year field value.
YearMonth	minus(ReadablePeriod period) Returns a copy of this year-month with the specified period taken away.
YearMonth	minusMonths(int months) Returns a copy of this year-month minus the specified number of months.
YearMonth	minusYears(int years) Returns a copy of this year-month minus the specified number of years.
YearMonth.Property	monthOfYear() Get the month of year field property which provides access to advanced functionality.
static YearMonth	now() Obtains a YearMonth set to the current system millisecond time using ISOChronology in the default time zone.
static YearMonth	now(Chronology chronology) Obtains a YearMonth set to the current system millisecond time using the specified chronology.
static YearMonth	now(DateTimeZone zone) Obtains a YearMonth set to the current system millisecond time using ISOChronology in the specified time zone.
static YearMonth	parse(String str) Parses a YearMonth from the specified string.
static YearMonth	parse(String str, DateTimeFormatter formatter) Parses a YearMonth from the specified string using a formatter.
YearMonth	plus(ReadablePeriod period) Returns a copy of this year-month with the specified period added.
YearMonth	plusMonths(int months) Returns a copy of this year-month plus the specified number of months.
YearMonth	plusYears(int years) Returns a copy of this year-month plus the specified number of years.
YearMonth.Property	property(DateTimeFieldType type) Gets the property object for the specified type, which contains many useful methods.
int	size() Gets the number of fields in this partial, which is two.
Interval	toInterval() Converts this object to an Interval representing the whole month.
Interval	toInterval(DateTimeZone zone) Converts this object to an Interval representing the whole month.
LocalDate	toLocalDate(int dayOfMonth) Converts this object to a LocalDate with the same year-month and chronology.
String	toString() Output the year-month in ISO8601 format (yyyy-MM).
String	toString(String pattern) Output the year-month using the specified format pattern.
String	toString(String pattern, Locale locale) Output the year-month using the specified format pattern.
YearMonth	withChronologyRetainFields(Chronology newChronology) Returns a copy of this year-month with the specified chronology.
YearMonth	withField(DateTimeFieldType fieldType, int value) Returns a copy of this year-month with the specified field set to a new value.
YearMonth	withFieldAdded(DurationFieldType fieldType, int amount) Returns a copy of this year-month with the value of the specified field increased.
YearMonth	withMonthOfYear(int monthOfYear) Returns a copy of this year-month with the month of year field updated.
YearMonth	withPeriodAdded(ReadablePeriod period, int scalar) Returns a copy of this year-month with the specified period added.
YearMonth	withYear(int year) Returns a copy of this year-month with the year field updated.
YearMonth.Property	year() Get the year field property which provides access to advanced functionality.

Methods inherited from class org.joda.time.base.BasePartial

getChronology, getValue, getValues, setValue, setValues

Methods inherited from class org.joda.time.base.AbstractPartial

compareTo, equals, get, getField, getFields, hashCode, indexOf, indexOf, indexOfSupported, indexOfSupported, isAfter, isBefore, isEqual, isSupported, toDateTime, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.joda.time.ReadablePartial

equals, get, getChronology, getField, getValue, hashCode, isSupported, toDateTime

Methods inherited from interface java.lang.Comparable

compareTo

Field Detail

YEAR

public static final int YEAR

The index of the year field in the field array

See Also:

Constant Field Values

MONTH_OF_YEAR

public static final int MONTH_OF_YEAR

The index of the monthOfYear field in the field array

See Also:

Constant Field Values

Constructor Detail

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:

now()

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:

now(DateTimeZone)

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:

now(Chronology)

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 Detail

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

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

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

See Also:

DateTimeFormat

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

Throws:

IllegalArgumentException

See Also:

DateTimeFormat