- * {@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 will query the {@link java.time.Clock#systemDefaultZone() system clock} in the default - * time-zone to obtain the current year-month. - * The zone and offset will be set based on the time-zone in the clock. - *
- * 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(java.time.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. - *
- * A {@code TemporalAccessor} represents some form of date and time information. - * This factory converts the arbitrary temporal object 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 in queries 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; - } - try { - if (ISOChrono.INSTANCE.equals(Chrono.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.getClass(), 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 yyyy-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} and - * {@link #get(TemporalField) get} methods will throw an exception. - *
- * 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 date-time. - * The supported fields are: - *
- * If the field is not a {@code ChronoField}, then the result of this method - * is obtained by invoking {@code TemporalField.doIsSupported(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 == EPOCH_MONTH || field == YEAR_OF_ERA || field == ERA; - } - return field != null && field.doIsSupported(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 a {@code DateTimeException}. - *
- * If the field is not a {@code ChronoField}, then the result of this method - * is obtained by invoking {@code TemporalField.doRange(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 - */ - @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 for 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 EPOCH_MONTH} which is too - * large to fit in an {@code int} and throw a {@code DateTimeException}. - * All other {@code ChronoField} instances will throw a {@code DateTimeException}. - *
- * If the field is not a {@code ChronoField}, then the result of this method - * is obtained by invoking {@code TemporalField.doGet(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 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 for 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 a {@code DateTimeException}. - *
- * If the field is not a {@code ChronoField}, then the result of this method - * is obtained by invoking {@code TemporalField.doGet(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 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 EPOCH_MONTH: return getEpochMonth(); - case YEAR_OF_ERA: return (year < 1 ? 1 - year : year); - case YEAR: return year; - case ERA: return (year < 1 ? 0 : 1); - } - throw new DateTimeException("Unsupported field: " + field.getName()); - } - return field.doGet(this); - } - - private long getEpochMonth() { - return ((year - 1970) * 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 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 - */ - 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 ISOChrono.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 new {@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 new {@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 a {@code DateTimeException}. - *
- * If the field is not a {@code ChronoField}, then the result of this method - * is obtained by invoking {@code TemporalField.doWith(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 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 EPOCH_MONTH: return plusMonths(newValue - getLong(EPOCH_MONTH)); - 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 DateTimeException("Unsupported field: " + field.getName()); - } - return field.doWith(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 period added. - *
- * This method returns a new year-month based on this year-month with the specified period added. - * The adder is typically {@link java.time.Period} but may be any other type implementing - * the {@link TemporalAdder} interface. - * The calculation is delegated to the specified adjuster, which typically calls - * back to {@link #plus(long, TemporalUnit)}. - *
- * This instance is immutable and unaffected by this method call. - * - * @param adder the adder to use, 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(TemporalAdder adder) { - return (YearMonth) adder.addTo(this); - } - - /** - * {@inheritDoc} - * @throws DateTimeException {@inheritDoc} - * @throws ArithmeticException {@inheritDoc} - */ - @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 DateTimeException("Unsupported unit: " + unit.getName()); - } - return unit.doPlus(this, amountToAdd); - } - - /** - * Returns a copy of this year-month with the specified period in 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 year-month with the specified period in 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 = (int)Math.floorMod(calcMonths, 12) + 1; - return with(newYear, newMonth); - } - - //----------------------------------------------------------------------- - /** - * Returns a copy of this year-month with the specified period subtracted. - *
- * This method returns a new year-month based on this year-month with the specified period subtracted. - * The subtractor is typically {@link java.time.Period} but may be any other type implementing - * the {@link TemporalSubtractor} interface. - * The calculation is delegated to the specified adjuster, which typically calls - * back to {@link #minus(long, TemporalUnit)}. - *
- * This instance is immutable and unaffected by this method call. - * - * @param subtractor the subtractor to use, 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(TemporalSubtractor subtractor) { - return (YearMonth) subtractor.subtractFrom(this); - } - - /** - * {@inheritDoc} - * @throws DateTimeException {@inheritDoc} - * @throws ArithmeticException {@inheritDoc} - */ - @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 year-month with the specified period in 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 year-month with the specified period in 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#EPOCH_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 (Chrono.from(temporal).equals(ISOChrono.INSTANCE) == false) {
- throw new DateTimeException("Adjustment only supported on ISO date-time");
- }
- return temporal.with(EPOCH_MONTH, getEpochMonth());
- }
-
- /**
- * Calculates the period between this year-month and another year-month in
- * terms of the specified unit.
- *
- * This calculates the period between two year-months in terms of a single unit.
- * 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 must be a {@code YearMonth}.
- * For example, the period in years between two year-months can be calculated
- * using {@code startYearMonth.periodUntil(endYearMonth, YEARS)}.
- *
- * The calculation returns a whole number, representing the number of
- * complete units between the two year-months.
- * For example, the period in decades between 2012-06 and 2032-05
- * will only be one decade as it is one month short of two decades.
- *
- * This method operates in association with {@link TemporalUnit#between}.
- * The result of this method is a {@code long} representing the amount of
- * the specified unit. By contrast, the result of {@code between} is an
- * object that can be used directly in addition/subtraction:
- *
- * 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 input temporal as
- * the second argument.
- *
- * This instance is immutable and unaffected by this method call.
- *
- * @param endYearMonth the end year-month, which must be a {@code YearMonth}, not null
- * @param unit the unit to measure the period in, not null
- * @return the amount of the period between this year-month and the end year-month
- * @throws DateTimeException if the period cannot be calculated
- * @throws ArithmeticException if numeric overflow occurs
- */
- @Override
- public long periodUntil(Temporal endYearMonth, TemporalUnit unit) {
- if (endYearMonth instanceof YearMonth == false) {
- Objects.requireNonNull(endYearMonth, "endYearMonth");
- throw new DateTimeException("Unable to calculate period between objects of two different types");
- }
- YearMonth end = (YearMonth) endYearMonth;
- if (unit instanceof ChronoUnit) {
- long monthsUntil = end.getEpochMonth() - getEpochMonth(); // 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 DateTimeException("Unsupported unit: " + unit.getName());
- }
- return unit.between(this, endYearMonth).getAmount();
- }
-
- //-----------------------------------------------------------------------
- /**
- * Returns a date formed from this year-month at the specified day-of-month.
- *
- * This combines this year-month and the specified day-of-month to form a {@code LocalDate}.
- * 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 instance is immutable and unaffected by this method call.
- *
- * @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 when the day is invalid for the year-month
- * @see #isValidDay(int)
- */
- public LocalDate atDay(int dayOfMonth) {
- return LocalDate.of(year, month, dayOfMonth);
- }
-
- //-----------------------------------------------------------------------
- /**
- * Compares this year-month to another year-month.
- *
- * 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;
- }
-
- /**
- * Is this year-month 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;
- }
-
- /**
- * Is this year-month 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 yyyy-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();
- }
-
- /**
- * Outputs this year-month as a {@code String} using the formatter.
- *
- * This year-month will be passed to the formatter
- * {@link DateTimeFormatter#print(TemporalAccessor) print method}.
- *
- * @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 toString(DateTimeFormatter formatter) {
- Objects.requireNonNull(formatter, "formatter");
- return formatter.print(this);
- }
-
- //-----------------------------------------------------------------------
- /**
- * Writes the object using a
- * dedicated serialized form.
- *
- * // these two lines are equivalent, but the second approach is recommended
- * temporal = thisYearMonth.adjustInto(temporal);
- * temporal = temporal.with(thisYearMonth);
- *
- *
- * long period = start.periodUntil(end, YEARS); // this method
- * dateTime.plus(YEARS.between(start, end)); // use in plus/minus
- *
- *
- * LocalDate date = year.atMonth(month).atDay(day);
- *
- *
- * out.writeByte(5); // identifies this as a Year
- * out.writeInt(year);
- * out.writeByte(month);
- *
- *
- * @return the instance of {@code Ser}, not null
- */
- private Object writeReplace() {
- return new Ser(Ser.YEAR_MONTH_TYPE, this);
- }
-
- /**
- * Defend against malicious streams.
- * @return never
- * @throws InvalidObjectException always
- */
- private Object readResolve() throws ObjectStreamException {
- 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);
- }
-
-}