Java example source code file (YearMonth.java)
The YearMonth.java Java example source code
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* Copyright (c) 2007-2012, Stephen Colebourne & Michael Nascimento Santos
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package java.time;
import static java.time.temporal.ChronoField.ERA;
import static java.time.temporal.ChronoField.MONTH_OF_YEAR;
import static java.time.temporal.ChronoField.PROLEPTIC_MONTH;
import static java.time.temporal.ChronoField.YEAR;
import static java.time.temporal.ChronoField.YEAR_OF_ERA;
import static java.time.temporal.ChronoUnit.CENTURIES;
import static java.time.temporal.ChronoUnit.DECADES;
import static java.time.temporal.ChronoUnit.ERAS;
import static java.time.temporal.ChronoUnit.MILLENNIA;
import static java.time.temporal.ChronoUnit.MONTHS;
import static java.time.temporal.ChronoUnit.YEARS;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.time.chrono.Chronology;
import java.time.chrono.IsoChronology;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeFormatterBuilder;
import java.time.format.DateTimeParseException;
import java.time.format.SignStyle;
import java.time.temporal.ChronoField;
import java.time.temporal.ChronoUnit;
import java.time.temporal.Temporal;
import java.time.temporal.TemporalAccessor;
import java.time.temporal.TemporalAdjuster;
import java.time.temporal.TemporalAmount;
import java.time.temporal.TemporalField;
import java.time.temporal.TemporalQueries;
import java.time.temporal.TemporalQuery;
import java.time.temporal.TemporalUnit;
import java.time.temporal.UnsupportedTemporalTypeException;
import java.time.temporal.ValueRange;
import java.util.Objects;
/**
* A year-month in the ISO-8601 calendar system, such as {@code 2007-12}.
* <p>
* {@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.
* <p>
* 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}.
* <p>
* 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.
*
* <p>
* This is a <a href="{@docRoot}/java/lang/doc-files/ValueBased.html">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<YearMonth>, Serializable {
/**
* Serialization version.
*/
private static final long serialVersionUID = 4183400860270640070L;
/**
* Parser.
*/
private static final DateTimeFormatter PARSER = new DateTimeFormatterBuilder()
.appendValue(YEAR, 4, 10, SignStyle.EXCEEDS_PAD)
.appendLiteral('-')
.appendValue(MONTH_OF_YEAR, 2)
.toFormatter();
/**
* The year.
*/
private final int year;
/**
* The month-of-year, not null.
*/
private final int month;
//-----------------------------------------------------------------------
/**
* Obtains the current year-month from the system clock in the default time-zone.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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}.
* <p>
* 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}.
* <p>
* 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;
}
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}.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* If the field is a {@link ChronoField} then the query is implemented here.
* The supported fields are:
* <ul>
* <li>{@code MONTH_OF_YEAR}
* <li>{@code PROLEPTIC_MONTH}
* <li>{@code YEAR_OF_ERA}
* <li>{@code YEAR}
* <li>{@code ERA}
* </ul>
* All other {@code ChronoField} instances will return false.
* <p>
* 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.
* <p>
* This checks if the specified unit can be added to, or subtracted from, this date-time.
* If false, then calling the {@link #plus(long, TemporalUnit)} and
* {@link #minus(long, TemporalUnit) minus} methods will throw an exception.
* <p>
* If the unit is a {@link ChronoUnit} then the query is implemented here.
* The supported units are:
* <ul>
* <li>{@code MONTHS}
* <li>{@code YEARS}
* <li>{@code DECADES}
* <li>{@code CENTURIES}
* <li>{@code MILLENNIA}
* <li>{@code ERAS}
* </ul>
* All other {@code ChronoUnit} instances will return false.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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}.
* <p>
* 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}.
* <p>
* 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.
* <p>
* 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}.
* <p>
* 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}.
* <p>
* 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.
* <p>
* 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}.
* <p>
* 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.
* <p>
* This method returns the primitive {@code int} value for the year.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* If the field is a {@link ChronoField} then the adjustment is implemented here.
* The supported fields behave as follows:
* <ul>
* <li>{@code MONTH_OF_YEAR} -
* Returns a {@code YearMonth} with the specified month-of-year.
* The year will be unchanged.
* <li>{@code PROLEPTIC_MONTH} -
* Returns a {@code YearMonth} with the specified proleptic-month.
* This completely replaces the year and month of this object.
* <li>{@code YEAR_OF_ERA} -
* Returns a {@code YearMonth} with the specified year-of-era
* The month and era will be unchanged.
* <li>{@code YEAR} -
* Returns a {@code YearMonth} with the specified year.
* The month will be unchanged.
* <li>{@code ERA} -
* Returns a {@code YearMonth} with the specified era.
* The month and year-of-era will be unchanged.
* </ul>
* <p>
* In all cases, if the new value is outside the valid range of values for the field
* then a {@code DateTimeException} will be thrown.
* <p>
* All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* If the field is a {@link ChronoUnit} then the addition is implemented here.
* The supported fields behave as follows:
* <ul>
* <li>{@code MONTHS} -
* Returns a {@code YearMonth} with the specified number of months added.
* This is equivalent to {@link #plusMonths(long)}.
* <li>{@code YEARS} -
* Returns a {@code YearMonth} with the specified number of years added.
* This is equivalent to {@link #plusYears(long)}.
* <li>{@code DECADES} -
* Returns a {@code YearMonth} with the specified number of decades added.
* This is equivalent to calling {@link #plusYears(long)} with the amount
* multiplied by 10.
* <li>{@code CENTURIES} -
* Returns a {@code YearMonth} with the specified number of centuries added.
* This is equivalent to calling {@link #plusYears(long)} with the amount
* multiplied by 100.
* <li>{@code MILLENNIA} -
* Returns a {@code YearMonth} with the specified number of millennia added.
* This is equivalent to calling {@link #plusYears(long)} with the amount
* multiplied by 1,000.
* <li>{@code ERAS} -
* Returns a {@code YearMonth} with the specified number of eras added.
* Only two eras are supported so the amount must be one, zero or minus one.
* If the amount is non-zero then the year is changed such that the year-of-era
* is unchanged.
* </ul>
* <p>
* All other {@code ChronoUnit} instances will throw an {@code UnsupportedTemporalTypeException}.
* <p>
* 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.
* <p>
* 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 year-month with the specified period in years added.
* <p>
* 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.
* <p>
* 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 amount subtracted.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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 year-month with the specified period in years subtracted.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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 <R> the type of the result
* @param query the query to invoke, not null
* @return the query result, null may be returned (defined by the query)
* @throws DateTimeException if unable to query (defined by the query)
* @throws ArithmeticException if numeric overflow occurs (defined by the query)
*/
@SuppressWarnings("unchecked")
@Override
public <R> R query(TemporalQuery
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