Module java.base

Package java.time

Class MonthDay

java.lang.Object

java.time.MonthDay

All Implemented Interfaces:

Serializable, Comparable<MonthDay>, TemporalAccessor, TemporalAdjuster

public final class MonthDay
extends Object
implements TemporalAccessor, TemporalAdjuster, Comparable<MonthDay>, Serializable

A month-day in the ISO-8601 calendar system, such as --12-03.

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

This class does not store or represent a year, time or time-zone. For example, the value "December 3rd" can be stored in a MonthDay.

Since a MonthDay does not possess a year, the leap day of February 29th is considered valid.

This class implements TemporalAccessor rather than Temporal. This is because it is not possible to define whether February 29th is valid or not without external information, preventing the implementation of plus/minus. Related to this, MonthDay only provides access to query and set the fields MONTH_OF_YEAR and DAY_OF_MONTH.

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 month-day.
LocalDate	atYear(int year)	Combines this month-day with a year to create a LocalDate.
int	compareTo(MonthDay other)	Compares this month-day to another month-day.
boolean	equals(Object obj)	Checks if this month-day is equal to another month-day.
String	format(DateTimeFormatter formatter)	Formats this month-day using the specified formatter.
static MonthDay	from(TemporalAccessor temporal)	Obtains an instance of MonthDay from a temporal object.
int	get(TemporalField field)	Gets the value of the specified field from this month-day as an int.
int	getDayOfMonth()	Gets the day-of-month field.
long	getLong(TemporalField field)	Gets the value of the specified field from this month-day 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	hashCode()	A hash code for this month-day.
boolean	isAfter(MonthDay other)	Checks if this month-day is after the specified month-day.
boolean	isBefore(MonthDay other)	Checks if this month-day is before the specified month-day.
boolean	isSupported(TemporalField field)	Checks if the specified field is supported.
boolean	isValidYear(int year)	Checks if the year is valid for this month-day.
static MonthDay	now()	Obtains the current month-day from the system clock in the default time-zone.
static MonthDay	now(Clock clock)	Obtains the current month-day from the specified clock.
static MonthDay	now(ZoneId zone)	Obtains the current month-day from the system clock in the specified time-zone.
static MonthDay	of(int month, int dayOfMonth)	Obtains an instance of MonthDay.
static MonthDay	of(Month month, int dayOfMonth)	Obtains an instance of MonthDay.
static MonthDay	parse(CharSequence text)	Obtains an instance of MonthDay from a text string such as --12-03.
static MonthDay	parse(CharSequence text, DateTimeFormatter formatter)	Obtains an instance of MonthDay from a text string using a specific formatter.
<R> R	query(TemporalQuery<R> query)	Queries this month-day using the specified query.
ValueRange	range(TemporalField field)	Gets the range of valid values for the specified field.
String	toString()	Outputs this month-day as a String, such as --12-03.
MonthDay	with(Month month)	Returns a copy of this MonthDay with the month-of-year altered.
MonthDay	withDayOfMonth(int dayOfMonth)	Returns a copy of this MonthDay with the day-of-month altered.
MonthDay	withMonth(int month)	Returns a copy of this MonthDay with the month-of-year altered.

Methods declared in class java.lang.Object

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

Method Details

now

public static MonthDay now()

Obtains the current month-day from the system clock in the default time-zone.

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

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

Returns:

the current month-day using the system clock and default time-zone, not null

now

public static MonthDay now(ZoneId zone)

Obtains the current month-day from the system clock in the specified time-zone.

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

now

public static MonthDay now(Clock clock)

Obtains the current month-day from the specified clock.

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

of

public static MonthDay of(Month month,
 int dayOfMonth)

Obtains an instance of MonthDay.

The day-of-month must be valid for the month within a leap year. Hence, for February, day 29 is valid.

For example, passing in April and day 31 will throw an exception, as there can never be April 31st in any year. By contrast, passing in February 29th is permitted, as that month-day can sometimes be valid.

Parameters:

month - the month-of-year to represent, not null

dayOfMonth - the day-of-month to represent, from 1 to 31

Returns:

the month-day, not null

Throws:

DateTimeException - if the value of any field is out of range, or if the day-of-month is invalid for the month

of

public static MonthDay of(int month,
 int dayOfMonth)

Obtains an instance of MonthDay.

The day-of-month must be valid for the month within a leap year. Hence, for month 2 (February), day 29 is valid.

For example, passing in month 4 (April) and day 31 will throw an exception, as there can never be April 31st in any year. By contrast, passing in February 29th is permitted, as that month-day can sometimes be valid.

Parameters:

month - the month-of-year to represent, from 1 (January) to 12 (December)

dayOfMonth - the day-of-month to represent, from 1 to 31

Returns:

the month-day, not null

Throws:

DateTimeException - if the value of any field is out of range, or if the day-of-month is invalid for the month

from

public static MonthDay from(TemporalAccessor temporal)

Obtains an instance of MonthDay from a temporal object.

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

The conversion extracts the MONTH_OF_YEAR and DAY_OF_MONTH 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, MonthDay::from.

Parameters:

temporal - the temporal object to convert, not null

Returns:

the month-day, not null

Throws:

DateTimeException - if unable to convert to a MonthDay

parse

public static MonthDay parse(CharSequence text)

Obtains an instance of MonthDay from a text string such as --12-03.

The string must represent a valid month-day. The format is --MM-dd.

Parameters:

text - the text to parse such as "--12-03", not null

Returns:

the parsed month-day, not null

Throws:

DateTimeParseException - if the text cannot be parsed

parse

public static MonthDay parse(CharSequence text,
 DateTimeFormatter formatter)

Obtains an instance of MonthDay from a text string using a specific formatter.

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

Parameters:

text - the text to parse, not null

formatter - the formatter to use, not null

Returns:

the parsed month-day, 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 month-day can be queried for the specified field. If false, then calling the range and get methods will throw an exception.

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

• MONTH_OF_YEAR
• YEAR

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 month-day, 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 month-day 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 month-day as an int.

This queries this month-day 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 month-day. 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 month-day as a long.

This queries this month-day 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 month-day. 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

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()

getDayOfMonth

public int getDayOfMonth()

Gets the day-of-month field.

This method returns the primitive int value for the day-of-month.

Returns:

the day-of-month, from 1 to 31

isValidYear

public boolean isValidYear(int year)

Checks if the year is valid for this month-day.

This method checks whether this month and day and the input year form a valid date. This can only return false for February 29th.

Parameters:

year - the year to validate

Returns:

true if the year is valid for this month-day

See Also:

• Year.isValidMonthDay(MonthDay)

withMonth

public MonthDay withMonth(int month)

Returns a copy of this MonthDay with the month-of-year altered.

This returns a month-day with the specified month. If the day-of-month is invalid for the specified month, the day will be adjusted to the last valid day-of-month.

This instance is immutable and unaffected by this method call.

Parameters:

month - the month-of-year to set in the returned month-day, from 1 (January) to 12 (December)

Returns:

a MonthDay based on this month-day with the requested month, not null

Throws:

DateTimeException - if the month-of-year value is invalid

with

public MonthDay with(Month month)

Returns a copy of this MonthDay with the month-of-year altered.

This returns a month-day with the specified month. If the day-of-month is invalid for the specified month, the day will be adjusted to the last valid day-of-month.

This instance is immutable and unaffected by this method call.

Parameters:

month - the month-of-year to set in the returned month-day, not null

Returns:

a MonthDay based on this month-day with the requested month, not null

withDayOfMonth

public MonthDay withDayOfMonth(int dayOfMonth)

Returns a copy of this MonthDay with the day-of-month altered.

This returns a month-day with the specified day-of-month. If the day-of-month is invalid for the month, an exception is thrown.

This instance is immutable and unaffected by this method call.

Parameters:

dayOfMonth - the day-of-month to set in the return month-day, from 1 to 31

Returns:

a MonthDay based on this month-day with the requested day, not null

Throws:

DateTimeException - if the day-of-month value is invalid, or if the day-of-month is invalid for the month

query

public <R> R query(TemporalQuery<R> query)

Queries this month-day using the specified query.

This queries this month-day 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 month-day.

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

The adjustment is equivalent to using Temporal.with(TemporalField, long) twice, passing ChronoField.MONTH_OF_YEAR and ChronoField.DAY_OF_MONTH as the fields. 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 = thisMonthDay.adjustInto(temporal);
   temporal = temporal.with(thisMonthDay);
 

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

format

public String format(DateTimeFormatter formatter)

Formats this month-day using the specified formatter.

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

Parameters:

formatter - the formatter to use, not null

Returns:

the formatted month-day string, not null

Throws:

DateTimeException - if an error occurs during printing

atYear

public LocalDate atYear(int year)

Combines this month-day with a year to create a LocalDate.

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

A month-day of February 29th will be adjusted to February 28th in the resulting date if the year is not a leap year.

This instance is immutable and unaffected by this method call.

Parameters:

year - the year to use, from MIN_YEAR to MAX_YEAR

Returns:

the local date formed from this month-day and the specified year, not null

Throws:

DateTimeException - if the year is outside the valid range of years

compareTo

public int compareTo(MonthDay other)

Compares this month-day to another month-day.

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

Specified by:

compareTo in interface Comparable<MonthDay>

Parameters:

other - the other month-day to compare to, not null

Returns:

the comparator value, that is less than zero if this is before other, zero if they are equal, greater than zero if this is after other

See Also:

• isBefore(java.time.MonthDay)
• isAfter(java.time.MonthDay)

isAfter

public boolean isAfter(MonthDay other)

Checks if this month-day is after the specified month-day.

Parameters:

other - the other month-day to compare to, not null

Returns:

true if this is after the specified month-day

isBefore

public boolean isBefore(MonthDay other)

Checks if this month-day is before the specified month-day.

Parameters:

other - the other month-day to compare to, not null

Returns:

true if this point is before the specified month-day

equals

public boolean equals(Object obj)

Checks if this month-day is equal to another month-day.

The comparison is based on the time-line position of the month-day within a year.

Overrides:

equals in class Object

Parameters:

obj - the object to check, null returns false

Returns:

true if this is equal to the other month-day

See Also:

• Object.hashCode()
• HashMap

hashCode

public int hashCode()

A hash code for this month-day.

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 month-day as a String, such as --12-03.

The output will be in the format --MM-dd:

Overrides:

toString in class Object

Returns:

a string representation of this month-day, not null