* {@code YearMonth} is an immutable date-time object that represents the combination * of a year and month. Any field that can be derived from a year and month, such as * quarter-of-year, can be obtained. *
* This class does not store or represent a day, time or time-zone. * For example, the value "October 2007" can be stored in a {@code YearMonth}. *
* The ISO-8601 calendar system is the modern civil calendar system used today * in most of the world. It is equivalent to the proleptic Gregorian calendar * system, in which today's rules for leap years are applied for all time. * For most applications written today, the ISO-8601 rules are entirely suitable. * However, any application that makes use of historical dates, and requires them * to be accurate will find the ISO-8601 approach unsuitable. * *
* This is a value-based
* class; use of identity-sensitive operations (including reference equality
* ({@code ==}), identity hash code, or synchronization) on instances of
* {@code YearMonth} may have unpredictable results and should be avoided.
* The {@code equals} method should be used for comparisons.
*
* @implSpec
* This class is immutable and thread-safe.
*
* @since 1.8
*/
public final class YearMonth
implements Temporal, TemporalAdjuster, Comparable
* This will query the {@link Clock#systemDefaultZone() system clock} in the default
* time-zone to obtain the current year-month.
*
* Using this method will prevent the ability to use an alternate clock for testing
* because the clock is hard-coded.
*
* @return the current year-month using the system clock and default time-zone, not null
*/
public static YearMonth now() {
return now(Clock.systemDefaultZone());
}
/**
* Obtains the current year-month from the system clock in the specified time-zone.
*
* This will query the {@link Clock#system(ZoneId) system clock} to obtain the current year-month.
* Specifying the time-zone avoids dependence on the default time-zone.
*
* Using this method will prevent the ability to use an alternate clock for testing
* because the clock is hard-coded.
*
* @param zone the zone ID to use, not null
* @return the current year-month using the system clock, not null
*/
public static YearMonth now(ZoneId zone) {
return now(Clock.system(zone));
}
/**
* Obtains the current year-month from the specified clock.
*
* This will query the specified clock to obtain the current year-month.
* Using this method allows the use of an alternate clock for testing.
* The alternate clock may be introduced using {@link Clock dependency injection}.
*
* @param clock the clock to use, not null
* @return the current year-month, not null
*/
public static YearMonth now(Clock clock) {
final LocalDate now = LocalDate.now(clock); // called once
return YearMonth.of(now.getYear(), now.getMonth());
}
//-----------------------------------------------------------------------
/**
* Obtains an instance of {@code YearMonth} from a year and month.
*
* @param year the year to represent, from MIN_YEAR to MAX_YEAR
* @param month the month-of-year to represent, not null
* @return the year-month, not null
* @throws DateTimeException if the year value is invalid
*/
public static YearMonth of(int year, Month month) {
Objects.requireNonNull(month, "month");
return of(year, month.getValue());
}
/**
* Obtains an instance of {@code YearMonth} from a year and month.
*
* @param year the year to represent, from MIN_YEAR to MAX_YEAR
* @param month the month-of-year to represent, from 1 (January) to 12 (December)
* @return the year-month, not null
* @throws DateTimeException if either field value is invalid
*/
public static YearMonth of(int year, int month) {
YEAR.checkValidValue(year);
MONTH_OF_YEAR.checkValidValue(month);
return new YearMonth(year, month);
}
//-----------------------------------------------------------------------
/**
* Obtains an instance of {@code YearMonth} from a temporal object.
*
* This obtains a year-month based on the specified temporal.
* A {@code TemporalAccessor} represents an arbitrary set of date and time information,
* which this factory converts to an instance of {@code YearMonth}.
*
* The conversion extracts the {@link ChronoField#YEAR YEAR} and
* {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} fields.
* The extraction is only permitted if the temporal object has an ISO
* chronology, or can be converted to a {@code LocalDate}.
*
* This method matches the signature of the functional interface {@link TemporalQuery}
* allowing it to be used as a query via method reference, {@code YearMonth::from}.
*
* @param temporal the temporal object to convert, not null
* @return the year-month, not null
* @throws DateTimeException if unable to convert to a {@code YearMonth}
*/
public static YearMonth from(TemporalAccessor temporal) {
if (temporal instanceof YearMonth) {
return (YearMonth) temporal;
}
Objects.requireNonNull(temporal, "temporal");
try {
if (IsoChronology.INSTANCE.equals(Chronology.from(temporal)) == false) {
temporal = LocalDate.from(temporal);
}
return of(temporal.get(YEAR), temporal.get(MONTH_OF_YEAR));
} catch (DateTimeException ex) {
throw new DateTimeException("Unable to obtain YearMonth from TemporalAccessor: " +
temporal + " of type " + temporal.getClass().getName(), ex);
}
}
//-----------------------------------------------------------------------
/**
* Obtains an instance of {@code YearMonth} from a text string such as {@code 2007-12}.
*
* The string must represent a valid year-month.
* The format must be {@code uuuu-MM}.
* Years outside the range 0000 to 9999 must be prefixed by the plus or minus symbol.
*
* @param text the text to parse such as "2007-12", not null
* @return the parsed year-month, not null
* @throws DateTimeParseException if the text cannot be parsed
*/
public static YearMonth parse(CharSequence text) {
return parse(text, PARSER);
}
/**
* Obtains an instance of {@code YearMonth} from a text string using a specific formatter.
*
* The text is parsed using the formatter, returning a year-month.
*
* @param text the text to parse, not null
* @param formatter the formatter to use, not null
* @return the parsed year-month, not null
* @throws DateTimeParseException if the text cannot be parsed
*/
public static YearMonth parse(CharSequence text, DateTimeFormatter formatter) {
Objects.requireNonNull(formatter, "formatter");
return formatter.parse(text, YearMonth::from);
}
//-----------------------------------------------------------------------
/**
* Constructor.
*
* @param year the year to represent, validated from MIN_YEAR to MAX_YEAR
* @param month the month-of-year to represent, validated from 1 (January) to 12 (December)
*/
private YearMonth(int year, int month) {
this.year = year;
this.month = month;
}
/**
* Returns a copy of this year-month with the new year and month, checking
* to see if a new object is in fact required.
*
* @param newYear the year to represent, validated from MIN_YEAR to MAX_YEAR
* @param newMonth the month-of-year to represent, validated not null
* @return the year-month, not null
*/
private YearMonth with(int newYear, int newMonth) {
if (year == newYear && month == newMonth) {
return this;
}
return new YearMonth(newYear, newMonth);
}
//-----------------------------------------------------------------------
/**
* Checks if the specified field is supported.
*
* This checks if this year-month can be queried for the specified field.
* If false, then calling the {@link #range(TemporalField) range},
* {@link #get(TemporalField) get} and {@link #with(TemporalField, long)}
* methods will throw an exception.
*
* If the field is a {@link ChronoField} then the query is implemented here.
* The supported fields are:
*
* If the field is not a {@code ChronoField}, then the result of this method
* is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)}
* passing {@code this} as the argument.
* Whether the field is supported is determined by the field.
*
* @param field the field to check, null returns false
* @return true if the field is supported on this year-month, false if not
*/
@Override
public boolean isSupported(TemporalField field) {
if (field instanceof ChronoField) {
return field == YEAR || field == MONTH_OF_YEAR ||
field == PROLEPTIC_MONTH || field == YEAR_OF_ERA || field == ERA;
}
return field != null && field.isSupportedBy(this);
}
/**
* Checks if the specified unit is supported.
*
* This checks if the specified unit can be added to, or subtracted from, this year-month.
* If false, then calling the {@link #plus(long, TemporalUnit)} and
* {@link #minus(long, TemporalUnit) minus} methods will throw an exception.
*
* If the unit is a {@link ChronoUnit} then the query is implemented here.
* The supported units are:
*
* If the unit is not a {@code ChronoUnit}, then the result of this method
* is obtained by invoking {@code TemporalUnit.isSupportedBy(Temporal)}
* passing {@code this} as the argument.
* Whether the unit is supported is determined by the unit.
*
* @param unit the unit to check, null returns false
* @return true if the unit can be added/subtracted, false if not
*/
@Override
public boolean isSupported(TemporalUnit unit) {
if (unit instanceof ChronoUnit) {
return unit == MONTHS || unit == YEARS || unit == DECADES || unit == CENTURIES || unit == MILLENNIA || unit == ERAS;
}
return unit != null && unit.isSupportedBy(this);
}
//-----------------------------------------------------------------------
/**
* Gets the range of valid values for the specified field.
*
* The range object expresses the minimum and maximum valid values for a field.
* This year-month is used to enhance the accuracy of the returned range.
* If it is not possible to return the range, because the field is not supported
* or for some other reason, an exception is thrown.
*
* If the field is a {@link ChronoField} then the query is implemented here.
* The {@link #isSupported(TemporalField) supported fields} will return
* appropriate range instances.
* All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
*
* If the field is not a {@code ChronoField}, then the result of this method
* is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)}
* passing {@code this} as the argument.
* Whether the range can be obtained is determined by the field.
*
* @param field the field to query the range for, not null
* @return the range of valid values for the field, not null
* @throws DateTimeException if the range for the field cannot be obtained
* @throws UnsupportedTemporalTypeException if the field is not supported
*/
@Override
public ValueRange range(TemporalField field) {
if (field == YEAR_OF_ERA) {
return (getYear() <= 0 ? ValueRange.of(1, Year.MAX_VALUE + 1) : ValueRange.of(1, Year.MAX_VALUE));
}
return Temporal.super.range(field);
}
/**
* Gets the value of the specified field from this year-month as an {@code int}.
*
* This queries this year-month for the value of the specified field.
* The returned value will always be within the valid range of values for the field.
* If it is not possible to return the value, because the field is not supported
* or for some other reason, an exception is thrown.
*
* If the field is a {@link ChronoField} then the query is implemented here.
* The {@link #isSupported(TemporalField) supported fields} will return valid
* values based on this year-month, except {@code PROLEPTIC_MONTH} which is too
* large to fit in an {@code int} and throw a {@code DateTimeException}.
* All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
*
* If the field is not a {@code ChronoField}, then the result of this method
* is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
* passing {@code this} as the argument. Whether the value can be obtained,
* and what the value represents, is determined by the field.
*
* @param field the field to get, not null
* @return 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
* @throws UnsupportedTemporalTypeException if the field is not supported or
* the range of values exceeds an {@code int}
* @throws ArithmeticException if numeric overflow occurs
*/
@Override // override for Javadoc
public int get(TemporalField field) {
return range(field).checkValidIntValue(getLong(field), field);
}
/**
* Gets the value of the specified field from this year-month as a {@code long}.
*
* This queries this year-month for the value of the specified field.
* If it is not possible to return the value, because the field is not supported
* or for some other reason, an exception is thrown.
*
* If the field is a {@link ChronoField} then the query is implemented here.
* The {@link #isSupported(TemporalField) supported fields} will return valid
* values based on this year-month.
* All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
*
* If the field is not a {@code ChronoField}, then the result of this method
* is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
* passing {@code this} as the argument. Whether the value can be obtained,
* and what the value represents, is determined by the field.
*
* @param field the field to get, not null
* @return the value for the field
* @throws DateTimeException if a value for the field cannot be obtained
* @throws UnsupportedTemporalTypeException if the field is not supported
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
public long getLong(TemporalField field) {
if (field instanceof ChronoField) {
switch ((ChronoField) field) {
case MONTH_OF_YEAR: return month;
case PROLEPTIC_MONTH: return getProlepticMonth();
case YEAR_OF_ERA: return (year < 1 ? 1 - year : year);
case YEAR: return year;
case ERA: return (year < 1 ? 0 : 1);
}
throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
}
return field.getFrom(this);
}
private long getProlepticMonth() {
return (year * 12L + month - 1);
}
//-----------------------------------------------------------------------
/**
* Gets the year field.
*
* This method returns the primitive {@code int} value for the year.
*
* The year returned by this method is proleptic as per {@code get(YEAR)}.
*
* @return the year, from MIN_YEAR to MAX_YEAR
*/
public int getYear() {
return year;
}
/**
* Gets the month-of-year field from 1 to 12.
*
* This method returns the month as an {@code int} from 1 to 12.
* Application code is frequently clearer if the enum {@link Month}
* is used by calling {@link #getMonth()}.
*
* @return the month-of-year, from 1 to 12
* @see #getMonth()
*/
public int getMonthValue() {
return month;
}
/**
* Gets the month-of-year field using the {@code Month} enum.
*
* This method returns the enum {@link Month} for the month.
* This avoids confusion as to what {@code int} values mean.
* If you need access to the primitive {@code int} value then the enum
* provides the {@link Month#getValue() int value}.
*
* @return the month-of-year, not null
* @see #getMonthValue()
*/
public Month getMonth() {
return Month.of(month);
}
//-----------------------------------------------------------------------
/**
* Checks if the year is a leap year, according to the ISO proleptic
* calendar system rules.
*
* This method applies the current rules for leap years across the whole time-line.
* In general, a year is a leap year if it is divisible by four without
* remainder. However, years divisible by 100, are not leap years, with
* the exception of years divisible by 400 which are.
*
* For example, 1904 is a leap year it is divisible by 4.
* 1900 was not a leap year as it is divisible by 100, however 2000 was a
* leap year as it is divisible by 400.
*
* The calculation is proleptic - applying the same rules into the far future and far past.
* This is historically inaccurate, but is correct for the ISO-8601 standard.
*
* @return true if the year is leap, false otherwise
*/
public boolean isLeapYear() {
return IsoChronology.INSTANCE.isLeapYear(year);
}
/**
* Checks if the day-of-month is valid for this year-month.
*
* This method checks whether this year and month and the input day form
* a valid date.
*
* @param dayOfMonth the day-of-month to validate, from 1 to 31, invalid value returns false
* @return true if the day is valid for this year-month
*/
public boolean isValidDay(int dayOfMonth) {
return dayOfMonth >= 1 && dayOfMonth <= lengthOfMonth();
}
/**
* Returns the length of the month, taking account of the year.
*
* This returns the length of the month in days.
* For example, a date in January would return 31.
*
* @return the length of the month in days, from 28 to 31
*/
public int lengthOfMonth() {
return getMonth().length(isLeapYear());
}
/**
* Returns the length of the year.
*
* This returns the length of the year in days, either 365 or 366.
*
* @return 366 if the year is leap, 365 otherwise
*/
public int lengthOfYear() {
return (isLeapYear() ? 366 : 365);
}
//-----------------------------------------------------------------------
/**
* Returns an adjusted copy of this year-month.
*
* This returns a {@code YearMonth}, based on this one, with the year-month adjusted.
* The adjustment takes place using the specified adjuster strategy object.
* Read the documentation of the adjuster to understand what adjustment will be made.
*
* A simple adjuster might simply set the one of the fields, such as the year field.
* A more complex adjuster might set the year-month to the next month that
* Halley's comet will pass the Earth.
*
* The result of this method is obtained by invoking the
* {@link TemporalAdjuster#adjustInto(Temporal)} method on the
* specified adjuster passing {@code this} as the argument.
*
* This instance is immutable and unaffected by this method call.
*
* @param adjuster the adjuster to use, not null
* @return a {@code YearMonth} based on {@code this} with the adjustment made, not null
* @throws DateTimeException if the adjustment cannot be made
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
public YearMonth with(TemporalAdjuster adjuster) {
return (YearMonth) adjuster.adjustInto(this);
}
/**
* Returns a copy of this year-month with the specified field set to a new value.
*
* This returns a {@code YearMonth}, based on this one, with the value
* for the specified field changed.
* This can be used to change any supported field, such as the year or month.
* If it is not possible to set the value, because the field is not supported or for
* some other reason, an exception is thrown.
*
* If the field is a {@link ChronoField} then the adjustment is implemented here.
* The supported fields behave as follows:
*
* In all cases, if the new value is outside the valid range of values for the field
* then a {@code DateTimeException} will be thrown.
*
* All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
*
* If the field is not a {@code ChronoField}, then the result of this method
* is obtained by invoking {@code TemporalField.adjustInto(Temporal, long)}
* passing {@code this} as the argument. In this case, the field determines
* whether and how to adjust the instant.
*
* This instance is immutable and unaffected by this method call.
*
* @param field the field to set in the result, not null
* @param newValue the new value of the field in the result
* @return a {@code YearMonth} based on {@code this} with the specified field set, not null
* @throws DateTimeException if the field cannot be set
* @throws UnsupportedTemporalTypeException if the field is not supported
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
public YearMonth with(TemporalField field, long newValue) {
if (field instanceof ChronoField) {
ChronoField f = (ChronoField) field;
f.checkValidValue(newValue);
switch (f) {
case MONTH_OF_YEAR: return withMonth((int) newValue);
case PROLEPTIC_MONTH: return plusMonths(newValue - getProlepticMonth());
case YEAR_OF_ERA: return withYear((int) (year < 1 ? 1 - newValue : newValue));
case YEAR: return withYear((int) newValue);
case ERA: return (getLong(ERA) == newValue ? this : withYear(1 - year));
}
throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
}
return field.adjustInto(this, newValue);
}
//-----------------------------------------------------------------------
/**
* Returns a copy of this {@code YearMonth} with the year altered.
*
* This instance is immutable and unaffected by this method call.
*
* @param year the year to set in the returned year-month, from MIN_YEAR to MAX_YEAR
* @return a {@code YearMonth} based on this year-month with the requested year, not null
* @throws DateTimeException if the year value is invalid
*/
public YearMonth withYear(int year) {
YEAR.checkValidValue(year);
return with(year, month);
}
/**
* Returns a copy of this {@code YearMonth} with the month-of-year altered.
*
* This instance is immutable and unaffected by this method call.
*
* @param month the month-of-year to set in the returned year-month, from 1 (January) to 12 (December)
* @return a {@code YearMonth} based on this year-month with the requested month, not null
* @throws DateTimeException if the month-of-year value is invalid
*/
public YearMonth withMonth(int month) {
MONTH_OF_YEAR.checkValidValue(month);
return with(year, month);
}
//-----------------------------------------------------------------------
/**
* Returns a copy of this year-month with the specified amount added.
*
* This returns a {@code YearMonth}, based on this one, with the specified amount added.
* The amount is typically {@link Period} but may be any other type implementing
* the {@link TemporalAmount} interface.
*
* The calculation is delegated to the amount object by calling
* {@link TemporalAmount#addTo(Temporal)}. The amount implementation is free
* to implement the addition in any way it wishes, however it typically
* calls back to {@link #plus(long, TemporalUnit)}. Consult the documentation
* of the amount implementation to determine if it can be successfully added.
*
* This instance is immutable and unaffected by this method call.
*
* @param amountToAdd the amount to add, not null
* @return a {@code YearMonth} based on this year-month with the addition made, not null
* @throws DateTimeException if the addition cannot be made
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
public YearMonth plus(TemporalAmount amountToAdd) {
return (YearMonth) amountToAdd.addTo(this);
}
/**
* Returns a copy of this year-month with the specified amount added.
*
* This returns a {@code YearMonth}, based on this one, with the amount
* in terms of the unit added. If it is not possible to add the amount, because the
* unit is not supported or for some other reason, an exception is thrown.
*
* If the field is a {@link ChronoUnit} then the addition is implemented here.
* The supported fields behave as follows:
*
* All other {@code ChronoUnit} instances will throw an {@code UnsupportedTemporalTypeException}.
*
* If the field is not a {@code ChronoUnit}, then the result of this method
* is obtained by invoking {@code TemporalUnit.addTo(Temporal, long)}
* passing {@code this} as the argument. In this case, the unit determines
* whether and how to perform the addition.
*
* This instance is immutable and unaffected by this method call.
*
* @param amountToAdd the amount of the unit to add to the result, may be negative
* @param unit the unit of the amount to add, not null
* @return a {@code YearMonth} based on this year-month with the specified amount added, not null
* @throws DateTimeException if the addition cannot be made
* @throws UnsupportedTemporalTypeException if the unit is not supported
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
public YearMonth plus(long amountToAdd, TemporalUnit unit) {
if (unit instanceof ChronoUnit) {
switch ((ChronoUnit) unit) {
case MONTHS: return plusMonths(amountToAdd);
case YEARS: return plusYears(amountToAdd);
case DECADES: return plusYears(Math.multiplyExact(amountToAdd, 10));
case CENTURIES: return plusYears(Math.multiplyExact(amountToAdd, 100));
case MILLENNIA: return plusYears(Math.multiplyExact(amountToAdd, 1000));
case ERAS: return with(ERA, Math.addExact(getLong(ERA), amountToAdd));
}
throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);
}
return unit.addTo(this, amountToAdd);
}
/**
* Returns a copy of this {@code YearMonth} with the specified number of years added.
*
* This instance is immutable and unaffected by this method call.
*
* @param yearsToAdd the years to add, may be negative
* @return a {@code YearMonth} based on this year-month with the years added, not null
* @throws DateTimeException if the result exceeds the supported range
*/
public YearMonth plusYears(long yearsToAdd) {
if (yearsToAdd == 0) {
return this;
}
int newYear = YEAR.checkValidIntValue(year + yearsToAdd); // safe overflow
return with(newYear, month);
}
/**
* Returns a copy of this {@code YearMonth} with the specified number of months added.
*
* This instance is immutable and unaffected by this method call.
*
* @param monthsToAdd the months to add, may be negative
* @return a {@code YearMonth} based on this year-month with the months added, not null
* @throws DateTimeException if the result exceeds the supported range
*/
public YearMonth plusMonths(long monthsToAdd) {
if (monthsToAdd == 0) {
return this;
}
long monthCount = year * 12L + (month - 1);
long calcMonths = monthCount + monthsToAdd; // safe overflow
int newYear = YEAR.checkValidIntValue(Math.floorDiv(calcMonths, 12));
int newMonth = Math.floorMod(calcMonths, 12) + 1;
return with(newYear, newMonth);
}
//-----------------------------------------------------------------------
/**
* Returns a copy of this year-month with the specified amount subtracted.
*
* This returns a {@code YearMonth}, based on this one, with the specified amount subtracted.
* The amount is typically {@link Period} but may be any other type implementing
* the {@link TemporalAmount} interface.
*
* The calculation is delegated to the amount object by calling
* {@link TemporalAmount#subtractFrom(Temporal)}. The amount implementation is free
* to implement the subtraction in any way it wishes, however it typically
* calls back to {@link #minus(long, TemporalUnit)}. Consult the documentation
* of the amount implementation to determine if it can be successfully subtracted.
*
* This instance is immutable and unaffected by this method call.
*
* @param amountToSubtract the amount to subtract, not null
* @return a {@code YearMonth} based on this year-month with the subtraction made, not null
* @throws DateTimeException if the subtraction cannot be made
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
public YearMonth minus(TemporalAmount amountToSubtract) {
return (YearMonth) amountToSubtract.subtractFrom(this);
}
/**
* Returns a copy of this year-month with the specified amount subtracted.
*
* This returns a {@code YearMonth}, based on this one, with the amount
* in terms of the unit subtracted. If it is not possible to subtract the amount,
* because the unit is not supported or for some other reason, an exception is thrown.
*
* This method is equivalent to {@link #plus(long, TemporalUnit)} with the amount negated.
* See that method for a full description of how addition, and thus subtraction, works.
*
* This instance is immutable and unaffected by this method call.
*
* @param amountToSubtract the amount of the unit to subtract from the result, may be negative
* @param unit the unit of the amount to subtract, not null
* @return a {@code YearMonth} based on this year-month with the specified amount subtracted, not null
* @throws DateTimeException if the subtraction cannot be made
* @throws UnsupportedTemporalTypeException if the unit is not supported
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
public YearMonth minus(long amountToSubtract, TemporalUnit unit) {
return (amountToSubtract == Long.MIN_VALUE ? plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit));
}
/**
* Returns a copy of this {@code YearMonth} with the specified number of years subtracted.
*
* This instance is immutable and unaffected by this method call.
*
* @param yearsToSubtract the years to subtract, may be negative
* @return a {@code YearMonth} based on this year-month with the years subtracted, not null
* @throws DateTimeException if the result exceeds the supported range
*/
public YearMonth minusYears(long yearsToSubtract) {
return (yearsToSubtract == Long.MIN_VALUE ? plusYears(Long.MAX_VALUE).plusYears(1) : plusYears(-yearsToSubtract));
}
/**
* Returns a copy of this {@code YearMonth} with the specified number of months subtracted.
*
* This instance is immutable and unaffected by this method call.
*
* @param monthsToSubtract the months to subtract, may be negative
* @return a {@code YearMonth} based on this year-month with the months subtracted, not null
* @throws DateTimeException if the result exceeds the supported range
*/
public YearMonth minusMonths(long monthsToSubtract) {
return (monthsToSubtract == Long.MIN_VALUE ? plusMonths(Long.MAX_VALUE).plusMonths(1) : plusMonths(-monthsToSubtract));
}
//-----------------------------------------------------------------------
/**
* Queries this year-month using the specified query.
*
* This queries this year-month using the specified query strategy object.
* The {@code 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
* {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the
* specified query passing {@code this} as the argument.
*
* @param
* This returns a temporal object of the same observable type as the input
* with the year and month changed to be the same as this.
*
* The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}
* passing {@link ChronoField#PROLEPTIC_MONTH} as the field.
* If the specified temporal object does not use the ISO calendar system then
* a {@code DateTimeException} is thrown.
*
* In most cases, it is clearer to reverse the calling pattern by using
* {@link Temporal#with(TemporalAdjuster)}:
*
* This instance is immutable and unaffected by this method call.
*
* @param temporal the target object to be adjusted, not null
* @return the adjusted object, not null
* @throws DateTimeException if unable to make the adjustment
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
public Temporal adjustInto(Temporal temporal) {
if (Chronology.from(temporal).equals(IsoChronology.INSTANCE) == false) {
throw new DateTimeException("Adjustment only supported on ISO date-time");
}
return temporal.with(PROLEPTIC_MONTH, getProlepticMonth());
}
/**
* Calculates the amount of time until another year-month in terms of the specified unit.
*
* This calculates the amount of time between two {@code YearMonth}
* objects in terms of a single {@code TemporalUnit}.
* The start and end points are {@code this} and the specified year-month.
* The result will be negative if the end is before the start.
* The {@code Temporal} passed to this method is converted to a
* {@code YearMonth} using {@link #from(TemporalAccessor)}.
* For example, the amount in years between two year-months can be calculated
* using {@code startYearMonth.until(endYearMonth, YEARS)}.
*
* The calculation returns a whole number, representing the number of
* complete units between the two year-months.
* For example, the amount in decades between 2012-06 and 2032-05
* will only be one decade as it is one month short of two decades.
*
* There are two equivalent ways of using this method.
* The first is to invoke this method.
* The second is to use {@link TemporalUnit#between(Temporal, Temporal)}:
*
* The calculation is implemented in this method for {@link ChronoUnit}.
* The units {@code MONTHS}, {@code YEARS}, {@code DECADES},
* {@code CENTURIES}, {@code MILLENNIA} and {@code ERAS} are supported.
* Other {@code ChronoUnit} values will throw an exception.
*
* If the unit is not a {@code ChronoUnit}, then the result of this method
* is obtained by invoking {@code TemporalUnit.between(Temporal, Temporal)}
* passing {@code this} as the first argument and the converted input temporal
* as the second argument.
*
* This instance is immutable and unaffected by this method call.
*
* @param endExclusive the end date, exclusive, which is converted to a {@code YearMonth}, not null
* @param unit the unit to measure the amount in, not null
* @return the amount of time between this year-month and the end year-month
* @throws DateTimeException if the amount cannot be calculated, or the end
* temporal cannot be converted to a {@code YearMonth}
* @throws UnsupportedTemporalTypeException if the unit is not supported
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
public long until(Temporal endExclusive, TemporalUnit unit) {
YearMonth end = YearMonth.from(endExclusive);
if (unit instanceof ChronoUnit) {
long monthsUntil = end.getProlepticMonth() - getProlepticMonth(); // no overflow
switch ((ChronoUnit) unit) {
case MONTHS: return monthsUntil;
case YEARS: return monthsUntil / 12;
case DECADES: return monthsUntil / 120;
case CENTURIES: return monthsUntil / 1200;
case MILLENNIA: return monthsUntil / 12000;
case ERAS: return end.getLong(ERA) - getLong(ERA);
}
throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);
}
return unit.between(this, end);
}
/**
* Formats this year-month using the specified formatter.
*
* This year-month will be passed to the formatter to produce a string.
*
* @param formatter the formatter to use, not null
* @return the formatted year-month string, not null
* @throws DateTimeException if an error occurs during printing
*/
public String format(DateTimeFormatter formatter) {
Objects.requireNonNull(formatter, "formatter");
return formatter.format(this);
}
//-----------------------------------------------------------------------
/**
* Combines this year-month with a day-of-month to create a {@code LocalDate}.
*
* This returns a {@code LocalDate} formed from this year-month and the specified day-of-month.
*
* The day-of-month value must be valid for the year-month.
*
* This method can be used as part of a chain to produce a date:
*
* This returns a {@code LocalDate} based on this year-month.
* The day-of-month is set to the last valid day of the month, taking
* into account leap years.
*
* This method can be used as part of a chain to produce a date:
*
* The comparison is based first on the value of the year, then on the value of the month.
* It is "consistent with equals", as defined by {@link Comparable}.
*
* @param other the other year-month to compare to, not null
* @return the comparator value, negative if less, positive if greater
*/
@Override
public int compareTo(YearMonth other) {
int cmp = (year - other.year);
if (cmp == 0) {
cmp = (month - other.month);
}
return cmp;
}
/**
* Checks if this year-month is after the specified year-month.
*
* @param other the other year-month to compare to, not null
* @return true if this is after the specified year-month
*/
public boolean isAfter(YearMonth other) {
return compareTo(other) > 0;
}
/**
* Checks if this year-month is before the specified year-month.
*
* @param other the other year-month to compare to, not null
* @return true if this point is before the specified year-month
*/
public boolean isBefore(YearMonth other) {
return compareTo(other) < 0;
}
//-----------------------------------------------------------------------
/**
* Checks if this year-month is equal to another year-month.
*
* The comparison is based on the time-line position of the year-months.
*
* @param obj the object to check, null returns false
* @return true if this is equal to the other year-month
*/
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj instanceof YearMonth) {
YearMonth other = (YearMonth) obj;
return year == other.year && month == other.month;
}
return false;
}
/**
* A hash code for this year-month.
*
* @return a suitable hash code
*/
@Override
public int hashCode() {
return year ^ (month << 27);
}
//-----------------------------------------------------------------------
/**
* Outputs this year-month as a {@code String}, such as {@code 2007-12}.
*
* The output will be in the format {@code uuuu-MM}:
*
* @return a string representation of this year-month, not null
*/
@Override
public String toString() {
int absYear = Math.abs(year);
StringBuilder buf = new StringBuilder(9);
if (absYear < 1000) {
if (year < 0) {
buf.append(year - 10000).deleteCharAt(1);
} else {
buf.append(year + 10000).deleteCharAt(0);
}
} else {
buf.append(year);
}
return buf.append(month < 10 ? "-0" : "-")
.append(month)
.toString();
}
//-----------------------------------------------------------------------
/**
* Writes the object using a
* dedicated serialized form.
* @serialData
*
*
* All other {@code ChronoField} instances will return false.
*
*
* All other {@code ChronoUnit} instances will return false.
*
*
*
*
*
* // these two lines are equivalent, but the second approach is recommended
* temporal = thisYearMonth.adjustInto(temporal);
* temporal = temporal.with(thisYearMonth);
*
*
* // these two lines are equivalent
* amount = start.until(end, MONTHS);
* amount = MONTHS.between(start, end);
*
* The choice should be made based on which makes the code more readable.
*
* LocalDate date = year.atMonth(month).atDay(day);
*
*
* @param dayOfMonth the day-of-month to use, from 1 to 31
* @return the date formed from this year-month and the specified day, not null
* @throws DateTimeException if the day is invalid for the year-month
* @see #isValidDay(int)
*/
public LocalDate atDay(int dayOfMonth) {
return LocalDate.of(year, month, dayOfMonth);
}
/**
* Returns a {@code LocalDate} at the end of the month.
*
* LocalDate date = year.atMonth(month).atEndOfMonth();
*
*
* @return the last valid date of this year-month, not null
*/
public LocalDate atEndOfMonth() {
return LocalDate.of(year, month, lengthOfMonth());
}
//-----------------------------------------------------------------------
/**
* Compares this year-month to another year-month.
*
* out.writeByte(12); // identifies a YearMonth
* out.writeInt(year);
* out.writeByte(month);
*
*
* @return the instance of {@code Ser}, not null
*/
@java.io.Serial
private Object writeReplace() {
return new Ser(Ser.YEAR_MONTH_TYPE, this);
}
/**
* Defend against malicious streams.
*
* @param s the stream to read
* @throws InvalidObjectException always
*/
@java.io.Serial
private void readObject(ObjectInputStream s) throws InvalidObjectException {
throw new InvalidObjectException("Deserialization via serialization delegate");
}
void writeExternal(DataOutput out) throws IOException {
out.writeInt(year);
out.writeByte(month);
}
static YearMonth readExternal(DataInput in) throws IOException {
int year = in.readInt();
byte month = in.readByte();
return YearMonth.of(year, month);
}
}