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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

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 * particular file as subject to the "Classpath" exception as provided

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 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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/*

 * This file is available under and governed by the GNU General Public

 * License version 2 only, as published by the Free Software Foundation.

 * However, the following notice accompanied the original version of this

 * file:

 *

 * Copyright (c) 2007-2012, Stephen Colebourne & Michael Nascimento Santos

 *

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions are met:

 *

 *  * Redistributions of source code must retain the above copyright notice,

 *    this list of conditions and the following disclaimer.

 *

 *  * Redistributions in binary form must reproduce the above copyright notice,

 *    this list of conditions and the following disclaimer in the documentation

 *    and/or other materials provided with the distribution.

 *

 *  * Neither the name of JSR-310 nor the names of its contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

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 */

package java.time;

import static java.time.temporal.ChronoField.ERA;

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.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 in the ISO-8601 calendar system, such as {@code 2007}.

 * <p>

 * {@code Year} is an immutable date-time object that represents a year.

 * Any field that can be derived from a year can be obtained.

 * <p>

 * <b>Note that years in the ISO chronology only align with years in the

 * Gregorian-Julian system for modern years. Parts of Russia did not switch to the

 * modern Gregorian/ISO rules until 1920.

 * As such, historical years must be treated with caution.</b>

 * <p>

 * This class does not store or represent a month, day, time or time-zone.

 * For example, the value "2007" can be stored in a {@code Year}.

 * <p>

 * Years represented by this class follow the ISO-8601 standard and use

 * the proleptic numbering system. Year 1 is preceded by year 0, then by year -1.

 * <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</a>

 * class; use of identity-sensitive operations (including reference equality

 * ({@code ==}), identity hash code, or synchronization) on instances of

 * {@code Year} 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 Year

        implements Temporal, TemporalAdjuster, Comparable<Year>, Serializable {

    /**

     * The minimum supported year, '-999,999,999'.

     */

    public static final int MIN_VALUE = -999_999_999;

    /**

     * The maximum supported year, '+999,999,999'.

     */

    public static final int MAX_VALUE = 999_999_999;

    /**

     * Serialization version.

     */

    private static final long serialVersionUID = -23038383694477807L;

    /**

     * Parser.

     */

    private static final DateTimeFormatter PARSER = new DateTimeFormatterBuilder()

        .appendValue(YEAR, 4, 10, SignStyle.EXCEEDS_PAD)

        .toFormatter();

    /**

     * The year being represented.

     */

    private final int year;

    //-----------------------------------------------------------------------

    /**

     * Obtains the current year from the system clock in the default time-zone.

     * <p>

     * This will query the {@link Clock#systemDefaultZone() system clock} in the default

     * time-zone to obtain the current year.

     * <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 using the system clock and default time-zone, not null

     */

    public static Year now() {

        return now(Clock.systemDefaultZone());

    }

    /**

     * Obtains the current year from the system clock in the specified time-zone.

     * <p>

     * This will query the {@link Clock#system(ZoneId) system clock} to obtain the current year.

     * 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 using the system clock, not null

     */

    public static Year now(ZoneId zone) {

        return now(Clock.system(zone));

    }

    /**

     * Obtains the current year from the specified clock.

     * <p>

     * This will query the specified clock to obtain the current year.

     * 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, not null

     */

    public static Year now(Clock clock) {

        final LocalDate now = LocalDate.now(clock);  // called once

        return Year.of(now.getYear());

    }

    //-----------------------------------------------------------------------

    /**

     * Obtains an instance of {@code Year}.

     * <p>

     * This method accepts a year value from the proleptic ISO calendar system.

     * <p>

     * The year 2AD/CE is represented by 2.<br>

     * The year 1AD/CE is represented by 1.<br>

     * The year 1BC/BCE is represented by 0.<br>

     * The year 2BC/BCE is represented by -1.<br>

     *

     * @param isoYear  the ISO proleptic year to represent, from {@code MIN_VALUE} to {@code MAX_VALUE}

     * @return the year, not null

     * @throws DateTimeException if the field is invalid

     */

    public static Year of(int isoYear) {

        YEAR.checkValidValue(isoYear);

        return new Year(isoYear);

    }

    //-----------------------------------------------------------------------

    /**

     * Obtains an instance of {@code Year} from a temporal object.

     * <p>

     * This obtains a year 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 Year}.

     * <p>

     * The conversion extracts the {@link ChronoField#YEAR year} field.

     * 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 as a query via method reference, {@code Year::from}.

     *

     * @param temporal  the temporal object to convert, not null

     * @return the year, not null

     * @throws DateTimeException if unable to convert to a {@code Year}

     */

    public static Year from(TemporalAccessor temporal) {

        if (temporal instanceof Year) {

            return (Year) temporal;

        }

        Objects.requireNonNull(temporal, "temporal");

        try {

            if (IsoChronology.INSTANCE.equals(Chronology.from(temporal)) == false) {

                temporal = LocalDate.from(temporal);

            }

            return of(temporal.get(YEAR));

        } catch (DateTimeException ex) {

            throw new DateTimeException("Unable to obtain Year from TemporalAccessor: " +

                    temporal + " of type " + temporal.getClass().getName(), ex);

        }

    }

    //-----------------------------------------------------------------------

    /**

     * Obtains an instance of {@code Year} from a text string such as {@code 2007}.

     * <p>

     * The string must represent a valid year.

     * 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", not null

     * @return the parsed year, not null

     * @throws DateTimeParseException if the text cannot be parsed

     */

    public static Year parse(CharSequence text) {

        return parse(text, PARSER);

    }

    /**

     * Obtains an instance of {@code Year} from a text string using a specific formatter.

     * <p>

     * The text is parsed using the formatter, returning a year.

     *

     * @param text  the text to parse, not null

     * @param formatter  the formatter to use, not null

     * @return the parsed year, not null

     * @throws DateTimeParseException if the text cannot be parsed

     */

    public static Year parse(CharSequence text, DateTimeFormatter formatter) {

        Objects.requireNonNull(formatter, "formatter");

        return formatter.parse(text, Year::from);

    }

    //-------------------------------------------------------------------------

    /**

     * 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.

     *

     * @param year  the year to check

     * @return true if the year is leap, false otherwise

     */

    public static boolean isLeap(long year) {

        return ((year & 3) == 0) && ((year % 100) != 0 || (year % 400) == 0);

    }

    //-----------------------------------------------------------------------

    /**

     * Constructor.

     *

     * @param year  the year to represent

     */

    private Year(int year) {

        this.year = year;

    }

    //-----------------------------------------------------------------------

    /**

     * Gets the year value.

     * <p>

     * The year returned by this method is proleptic as per {@code get(YEAR)}.

     *

     * @return the year, {@code MIN_VALUE} to {@code MAX_VALUE}

     */

    public int getValue() {

        return year;

    }

    //-----------------------------------------------------------------------

    /**

     * Checks if the specified field is supported.

     * <p>

     * This checks if this year 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 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, false if not

     */

    @Override

    public boolean isSupported(TemporalField field) {

        if (field instanceof ChronoField) {

            return field == YEAR || 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 year.

     * 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 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 == 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 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 (year <= 0 ? ValueRange.of(1, MAX_VALUE + 1) : ValueRange.of(1, MAX_VALUE));

        }

        return Temporal.super.range(field);

    }

    /**

     * Gets the value of the specified field from this year as an {@code int}.

     * <p>

     * This queries this year 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.

     * <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.

     * 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 as a {@code long}.

     * <p>

     * This queries this year 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.

     * <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.

     * 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 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);

    }

    //-----------------------------------------------------------------------

    /**

     * 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>