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java.time

public final Class MonthDay

extends Object
implements TemporalAccessor, TemporalAdjuster, Comparable<MonthDay>, Serializable
Class Inheritance
All Implemented Interfaces
java.io.Serializable, java.lang.Comparable, java.time.temporal.TemporalAdjuster, java.time.temporal.TemporalAccessor
Annotations
@ValueBased
Static Imports
java.time.temporal.ChronoField.DAY_OF_MONTH, .ChronoField.MONTH_OF_YEAR
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 Specification

This class is immutable and thread-safe.

Since
1.8

Field Summary

Modifier and TypeField and Description
private final transient byte
day

private final transient byte
month

private static final DateTimeFormatter
PARSER

Parser.

private static final ObjectStreamField[]
serialPersistentFields

For backward compatibility of the serialized MonthDay.class object, explicitly declare the types of the serialized fields as defined in Java SE 8.

private static final long
serialVersionUID

Serialization version.

Constructor Summary

AccessConstructor and Description
private
MonthDay(int
the month-of-year to represent, validated from 1 to 12
month, int
the day-of-month to represent, validated from 1 to 29-31
dayOfMonth)

Constructor, previously validated.

Method Summary

Modifier and TypeMethod and Description
public Temporal

Returns:

the adjusted object, not null
adjustInto(Temporal
the target object to be adjusted, not null
temporal)

Implements java.time.temporal.TemporalAdjuster.adjustInto.

Adjusts the specified temporal object to have this month-day.

public LocalDate

Returns:

the local date formed from this month-day and the specified year, not null
atYear(int
the year to use, from MIN_YEAR to MAX_YEAR
year)

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

public int

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
compareTo(MonthDay
the other month-day to compare to, not null
other)

Implements java.lang.Comparable.compareTo.

Compares this month-day to another month-day.

public boolean

Returns:

true if this is equal to the other month-day
equals(Object
the object to check, null returns false
obj)

Overrides java.lang.Object.equals.

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

public String

Returns:

the formatted month-day string, not null
format(DateTimeFormatter
the formatter to use, not null
formatter)

Formats this month-day using the specified formatter.

public static MonthDay

Returns:

the month-day, not null
from(TemporalAccessor
the temporal object to convert, not null
temporal)

Obtains an instance of MonthDay from a temporal object.

public int

Returns:

the value for the field
get(TemporalField
the field to get, not null
field)

Overrides default java.time.temporal.TemporalAccessor.get.

Gets the value of the specified field from this month-day as an int.

public int

Returns:

the day-of-month, from 1 to 31
getDayOfMonth()

Gets the day-of-month field.

public long

Returns:

the value for the field
getLong(TemporalField
the field to get, not null
field)

Implements java.time.temporal.TemporalAccessor.getLong.

Gets the value of the specified field from this month-day as a long.

public Month

Returns:

the month-of-year, not null
getMonth()

Gets the month-of-year field using the Month enum.

public int

Returns:

the month-of-year, from 1 to 12
getMonthValue()

Gets the month-of-year field from 1 to 12.

public int

Returns:

a suitable hash code
hashCode()

Overrides java.lang.Object.hashCode.

A hash code for this month-day.

public boolean

Returns:

true if this is after the specified month-day
isAfter(MonthDay
the other month-day to compare to, not null
other)

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

public boolean

Returns:

true if this point is before the specified month-day
isBefore(MonthDay
the other month-day to compare to, not null
other)

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

public boolean

Returns:

true if the field is supported on this month-day, false if not
isSupported(TemporalField
the field to check, null returns false
field)

Implements java.time.temporal.TemporalAccessor.isSupported.

Checks if the specified field is supported.

public boolean

Returns:

true if the year is valid for this month-day
isValidYear(int
the year to validate
year)

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

public static MonthDay

Returns:

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

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

public static MonthDay

Returns:

the current month-day using the system clock, not null
now(ZoneId
the zone ID to use, not null
zone)

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

public static MonthDay

Returns:

the current month-day, not null
now(Clock
the clock to use, not null
clock)

Obtains the current month-day from the specified clock.

public static MonthDay

Returns:

the month-day, not null
of(Month
the month-of-year to represent, not null
month, int
the day-of-month to represent, from 1 to 31
dayOfMonth)

Obtains an instance of MonthDay.

public static MonthDay

Returns:

the month-day, not null
of(int
the month-of-year to represent, from 1 (January) to 12 (December)
month, int
the day-of-month to represent, from 1 to 31
dayOfMonth)

Obtains an instance of MonthDay.

public static MonthDay

Returns:

the parsed month-day, not null
parse(CharSequence
the text to parse such as "--12-03", not null
text)

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

public static MonthDay

Returns:

the parsed month-day, not null
parse(CharSequence
the text to parse, not null
text, DateTimeFormatter
the formatter to use, not null
formatter)

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

public <
the type of the result
R> R

Returns:

the query result, null may be returned (defined by the query)
query(TemporalQuery<R>
the query to invoke, not null
query)

Overrides default java.time.temporal.TemporalAccessor.query.

Queries this month-day using the specified query.

public ValueRange

Returns:

the range of valid values for the field, not null
range(TemporalField
the field to query the range for, not null
field)

Overrides default java.time.temporal.TemporalAccessor.range.

Gets the range of valid values for the specified field.

pack-priv static MonthDay
readExternal(DataInput in)

private void
readObject(ObjectInputStream
the stream to read
s)

Defend against malicious streams.

public String

Returns:

a string representation of this month-day, not null
toString()

Overrides java.lang.Object.toString.

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

public MonthDay

Returns:

a MonthDay based on this month-day with the requested month, not null
with(Month
the month-of-year to set in the returned month-day, not null
month)

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

public MonthDay

Returns:

a MonthDay based on this month-day with the requested day, not null
withDayOfMonth(int
the day-of-month to set in the return month-day, from 1 to 31
dayOfMonth)

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

public MonthDay

Returns:

a MonthDay based on this month-day with the requested month, not null
withMonth(int
the month-of-year to set in the returned month-day, from 1 (January) to 12 (December)
month)

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

pack-priv void
writeExternal(DataOutput out)

private Object

Returns:

the instance of Ser, not null
writeReplace()

Writes the object using a dedicated serialized form.

Inherited from java.lang.Object:
clonefinalizegetClassnotifynotifyAllwaitwaitwait

Field Detail

dayback to summary
private final transient byte day
monthback to summary
private final transient byte month
PARSERback to summary
private static final DateTimeFormatter PARSER

Parser.

serialPersistentFieldsback to summary
private static final ObjectStreamField[] serialPersistentFields

For backward compatibility of the serialized MonthDay.class object, explicitly declare the types of the serialized fields as defined in Java SE 8. Instances of MonthDay are serialized using the dedicated serialized form by writeReplace.

Annotations
@Serial
Serial Fields:
month:int
The month-of-year.
day:int
The day-of-month.
serialVersionUIDback to summary
private static final long serialVersionUID

Serialization version.

Annotations
@Serial

Constructor Detail

MonthDayback to summary
private MonthDay(int month, int dayOfMonth)

Constructor, previously validated.

Parameters
month:int

the month-of-year to represent, validated from 1 to 12

dayOfMonth:int

the day-of-month to represent, validated from 1 to 29-31

Method Detail

adjustIntoback to summary
public Temporal adjustInto(Temporal temporal)

Implements java.time.temporal.TemporalAdjuster.adjustInto.

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.

Parameters
temporal:Temporal

the target object to be adjusted, not null

Returns:Temporal

the adjusted object, not null

Annotations
@Override
Exceptions
DateTimeException:
if unable to make the adjustment
ArithmeticException:
if numeric overflow occurs
atYearback to summary
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:int

the year to use, from MIN_YEAR to MAX_YEAR

Returns:LocalDate

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

Exceptions
DateTimeException:
if the year is outside the valid range of years
compareToback to summary
public int compareTo(MonthDay other)

Implements java.lang.Comparable.compareTo.

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.

Parameters
other:MonthDay

the other month-day to compare to, not null

Returns:int

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

Annotations
@Override
See Also
isBefore, isAfter
equalsback to summary
public boolean equals(Object obj)

Overrides java.lang.Object.equals.

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.

Parameters
obj:Object

the object to check, null returns false

Returns:boolean

true if this is equal to the other month-day

Annotations
@Override
formatback to summary
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:DateTimeFormatter

the formatter to use, not null

Returns:String

the formatted month-day string, not null

Exceptions
DateTimeException:
if an error occurs during printing
fromback to summary
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:TemporalAccessor

the temporal object to convert, not null

Returns:MonthDay

the month-day, not null

Exceptions
DateTimeException:
if unable to convert to a MonthDay
getback to summary
public int get(TemporalField field)

Overrides default java.time.temporal.TemporalAccessor.get.

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.

Parameters
field:TemporalField

the field to get, not null

Returns:int

the value for the field

Annotations
@Override
Exceptions
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
getDayOfMonthback to summary
public int getDayOfMonth()

Gets the day-of-month field.

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

Returns:int

the day-of-month, from 1 to 31

getLongback to summary
public long getLong(TemporalField field)

Implements java.time.temporal.TemporalAccessor.getLong.

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.

Parameters
field:TemporalField

the field to get, not null

Returns:long

the value for the field

Annotations
@Override
Exceptions
DateTimeException:
if a value for the field cannot be obtained
UnsupportedTemporalTypeException:
if the field is not supported
ArithmeticException:
if numeric overflow occurs
getMonthback to summary
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:Month

the month-of-year, not null

See Also
getMonthValue()
getMonthValueback to summary
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:int

the month-of-year, from 1 to 12

See Also
getMonth()
hashCodeback to summary
public int hashCode()

Overrides java.lang.Object.hashCode.

A hash code for this month-day.

Returns:int

a suitable hash code

Annotations
@Override
isAfterback to summary
public boolean isAfter(MonthDay other)

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

Parameters
other:MonthDay

the other month-day to compare to, not null

Returns:boolean

true if this is after the specified month-day

isBeforeback to summary
public boolean isBefore(MonthDay other)

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

Parameters
other:MonthDay

the other month-day to compare to, not null

Returns:boolean

true if this point is before the specified month-day

isSupportedback to summary
public boolean isSupported(TemporalField field)

Implements java.time.temporal.TemporalAccessor.isSupported.

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.

Parameters
field:TemporalField

the field to check, null returns false

Returns:boolean

true if the field is supported on this month-day, false if not

Annotations
@Override
isValidYearback to summary
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:int

the year to validate

Returns:boolean

true if the year is valid for this month-day

See Also
Year#isValidMonthDay(MonthDay)
nowback to summary
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:MonthDay

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

nowback to summary
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:ZoneId

the zone ID to use, not null

Returns:MonthDay

the current month-day using the system clock, not null

nowback to summary
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:Clock

the clock to use, not null

Returns:MonthDay

the current month-day, not null

ofback to summary
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:Month

the month-of-year to represent, not null

dayOfMonth:int

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

Returns:MonthDay

the month-day, not null

Exceptions
DateTimeException:
if the value of any field is out of range, or if the day-of-month is invalid for the month
ofback to summary
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:int

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

dayOfMonth:int

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

Returns:MonthDay

the month-day, not null

Exceptions
DateTimeException:
if the value of any field is out of range, or if the day-of-month is invalid for the month
parseback to summary
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:CharSequence

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

Returns:MonthDay

the parsed month-day, not null

Exceptions
DateTimeParseException:
if the text cannot be parsed
parseback to summary
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:CharSequence

the text to parse, not null

formatter:DateTimeFormatter

the formatter to use, not null

Returns:MonthDay

the parsed month-day, not null

Exceptions
DateTimeParseException:
if the text cannot be parsed
queryback to summary
public <R> R query(TemporalQuery<R> query)

Overrides default java.time.temporal.TemporalAccessor.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.

Parameters
<R>
the type of the result
query:TemporalQuery<R>

the query to invoke, not null

Returns:R

the query result, null may be returned (defined by the query)

Annotations
@SuppressWarnings:unchecked
@Override
Exceptions
DateTimeException:
if unable to query (defined by the query)
ArithmeticException:
if numeric overflow occurs (defined by the query)
rangeback to summary
public ValueRange range(TemporalField field)

Overrides default java.time.temporal.TemporalAccessor.range.

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.

Parameters
field:TemporalField

the field to query the range for, not null

Returns:ValueRange

the range of valid values for the field, not null

Annotations
@Override
Exceptions
DateTimeException:
if the range for the field cannot be obtained
UnsupportedTemporalTypeException:
if the field is not supported
readExternalback to summary
pack-priv static MonthDay readExternal(DataInput in) throws IOException
readObjectback to summary
private void readObject(ObjectInputStream s) throws InvalidObjectException

Defend against malicious streams.

Parameters
s:ObjectInputStream

the stream to read

Annotations
@Serial
Exceptions
InvalidObjectException:
always
toStringback to summary
public String toString()

Overrides java.lang.Object.toString.

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

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

Returns:String

a string representation of this month-day, not null

Annotations
@Override
withback to summary
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:Month

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

Returns:MonthDay

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

withDayOfMonthback to summary
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:int

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

Returns:MonthDay

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

Exceptions
DateTimeException:
if the day-of-month value is invalid, or if the day-of-month is invalid for the month
withMonthback to summary
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:int

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

Returns:MonthDay

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

Exceptions
DateTimeException:
if the month-of-year value is invalid
writeExternalback to summary
pack-priv void writeExternal(DataOutput out) throws IOException
writeReplaceback to summary
private Object writeReplace()

Writes the object using a dedicated serialized form.

Returns:Object

the instance of Ser, not null

Annotations
@Serial
Serial data 
 out.writeByte(13);  // identifies a MonthDay
 out.writeByte(month);
 out.writeByte(day);