https://openjdk.java.net/ 
/*
 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * 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
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 * 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) 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
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package java.time.chrono;

import static java.time.temporal.ChronoField.ALIGNED_DAY_OF_WEEK_IN_MONTH;
import static java.time.temporal.ChronoField.ALIGNED_DAY_OF_WEEK_IN_YEAR;
import static java.time.temporal.ChronoField.ALIGNED_WEEK_OF_MONTH;
import static java.time.temporal.ChronoField.ALIGNED_WEEK_OF_YEAR;
import static java.time.temporal.ChronoField.DAY_OF_MONTH;
import static java.time.temporal.ChronoField.DAY_OF_WEEK;
import static java.time.temporal.ChronoField.DAY_OF_YEAR;
import static java.time.temporal.ChronoField.EPOCH_DAY;
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.DAYS;
import static java.time.temporal.ChronoUnit.MONTHS;
import static java.time.temporal.ChronoUnit.WEEKS;
import static java.time.temporal.TemporalAdjusters.nextOrSame;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectStreamException;
import java.io.Serializable;
import java.time.DateTimeException;
import java.time.DayOfWeek;
import java.time.format.ResolverStyle;
import java.time.temporal.ChronoField;
import java.time.temporal.TemporalAdjusters;
import java.time.temporal.TemporalField;
import java.time.temporal.ValueRange;
import java.util.Comparator;
import java.util.HashSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Objects;
import java.util.ServiceLoader;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

import sun.util.logging.PlatformLogger;


An abstract implementation of a calendar system, used to organize and identify dates.


The main date and time API is built on the ISO calendar system.
The chronology operates behind the scenes to represent the general concept of a calendar system.

 See Chronology for more details. 
Implementation Requirements: This class is separated from the Chronology interface so that the static methods are not inherited. While Chronology can be implemented directly, it is strongly recommended to extend this abstract class instead. 

This class must be implemented with care to ensure other classes operate correctly.
All implementations that can be instantiated must be final, immutable and thread-safe.
Subclasses should be Serializable wherever possible.
Since:1.8
/**
 * An abstract implementation of a calendar system, used to organize and identify dates.
 * <p>
 * The main date and time API is built on the ISO calendar system.
 * The chronology operates behind the scenes to represent the general concept of a calendar system.
 * <p>
 * See {@link Chronology} for more details.
 *
 * @implSpec
 * This class is separated from the {@code Chronology} interface so that the static methods
 * are not inherited. While {@code Chronology} can be implemented directly, it is strongly
 * recommended to extend this abstract class instead.
 * <p>
 * This class must be implemented with care to ensure other classes operate correctly.
 * All implementations that can be instantiated must be final, immutable and thread-safe.
 * Subclasses should be Serializable wherever possible.
 *
 * @since 1.8
 */
public abstract class AbstractChronology implements Chronology {

    
Map of available calendars by ID.

/**
     * Map of available calendars by ID.
     */
    private static final ConcurrentHashMap<String, Chronology> CHRONOS_BY_ID = new ConcurrentHashMap<>();
    
Map of available calendars by calendar type.

/**
     * Map of available calendars by calendar type.
     */
    private static final ConcurrentHashMap<String, Chronology> CHRONOS_BY_TYPE = new ConcurrentHashMap<>();

    
Register a Chronology by its ID and type for lookup by of(String). Chronologies must not be registered until they are completely constructed. Specifically, not in the constructor of Chronology. 
Params:
  • chrono – the chronology to register; not null
Returns:the already registered Chronology if any, may be null
/**
     * Register a Chronology by its ID and type for lookup by {@link #of(String)}.
     * Chronologies must not be registered until they are completely constructed.
     * Specifically, not in the constructor of Chronology.
     *
     * @param chrono the chronology to register; not null
     * @return the already registered Chronology if any, may be null
     */
    static Chronology registerChrono(Chronology chrono) {
        return registerChrono(chrono, chrono.getId());
    }

    
Register a Chronology by ID and type for lookup by of(String). Chronos must not be registered until they are completely constructed. Specifically, not in the constructor of Chronology. 
Params:
  • chrono – the chronology to register; not null
  • id – the ID to register the chronology; not null
Returns:the already registered Chronology if any, may be null
/**
     * Register a Chronology by ID and type for lookup by {@link #of(String)}.
     * Chronos must not be registered until they are completely constructed.
     * Specifically, not in the constructor of Chronology.
     *
     * @param chrono the chronology to register; not null
     * @param id the ID to register the chronology; not null
     * @return the already registered Chronology if any, may be null
     */
    static Chronology registerChrono(Chronology chrono, String id) {
        Chronology prev = CHRONOS_BY_ID.putIfAbsent(id, chrono);
        if (prev == null) {
            String type = chrono.getCalendarType();
            if (type != null) {
                CHRONOS_BY_TYPE.putIfAbsent(type, chrono);
            }
        }
        return prev;
    }

    
Initialization of the maps from id and type to Chronology. The ServiceLoader is used to find and register any implementations of AbstractChronology found in the bootclass loader. The built-in chronologies are registered explicitly. Calendars configured via the Thread's context classloader are local to that thread and are ignored. 

The initialization is done only once using the registration
of the IsoChronology as the test and the final step.
Multiple threads may perform the initialization concurrently.
Only the first registration of each Chronology is retained by the
ConcurrentHashMap.

Returns:true if the cache was initialized
/**
     * Initialization of the maps from id and type to Chronology.
     * The ServiceLoader is used to find and register any implementations
     * of {@link java.time.chrono.AbstractChronology} found in the bootclass loader.
     * The built-in chronologies are registered explicitly.
     * Calendars configured via the Thread's context classloader are local
     * to that thread and are ignored.
     * <p>
     * The initialization is done only once using the registration
     * of the IsoChronology as the test and the final step.
     * Multiple threads may perform the initialization concurrently.
     * Only the first registration of each Chronology is retained by the
     * ConcurrentHashMap.
     * @return true if the cache was initialized
     */
    private static boolean initCache() {
        if (CHRONOS_BY_ID.get("ISO") == null) {
            // Initialization is incomplete

            // Register built-in Chronologies
            registerChrono(HijrahChronology.INSTANCE);
            registerChrono(JapaneseChronology.INSTANCE);
            registerChrono(MinguoChronology.INSTANCE);
            registerChrono(ThaiBuddhistChronology.INSTANCE);

            // Register Chronologies from the ServiceLoader
            @SuppressWarnings("rawtypes")
            ServiceLoader<AbstractChronology> loader =  ServiceLoader.load(AbstractChronology.class, null);
            for (AbstractChronology chrono : loader) {
                String id = chrono.getId();
                if (id.equals("ISO") || registerChrono(chrono) != null) {
                    // Log the attempt to replace an existing Chronology
                    PlatformLogger logger = PlatformLogger.getLogger("java.time.chrono");
                    logger.warning("Ignoring duplicate Chronology, from ServiceLoader configuration "  + id);
                }
            }

            // finally, register IsoChronology to mark initialization is complete
            registerChrono(IsoChronology.INSTANCE);
            return true;
        }
        return false;
    }

    //-----------------------------------------------------------------------
    
Obtains an instance of Chronology from a locale. 
 See Chronology.ofLocale(Locale). 
Params:
  • locale –  the locale to use to obtain the calendar system, not null
Throws:
Returns:the calendar system associated with the locale, not null
/**
     * Obtains an instance of {@code Chronology} from a locale.
     * <p>
     * See {@link Chronology#ofLocale(Locale)}.
     *
     * @param locale  the locale to use to obtain the calendar system, not null
     * @return the calendar system associated with the locale, not null
     * @throws java.time.DateTimeException if the locale-specified calendar cannot be found
     */
    static Chronology ofLocale(Locale locale) {
        Objects.requireNonNull(locale, "locale");
        String type = locale.getUnicodeLocaleType("ca");
        if (type == null || "iso".equals(type) || "iso8601".equals(type)) {
            return IsoChronology.INSTANCE;
        }
        // Not pre-defined; lookup by the type
        do {
            Chronology chrono = CHRONOS_BY_TYPE.get(type);
            if (chrono != null) {
                return chrono;
            }
            // If not found, do the initialization (once) and repeat the lookup
        } while (initCache());

        // Look for a Chronology using ServiceLoader of the Thread's ContextClassLoader
        // Application provided Chronologies must not be cached
        @SuppressWarnings("rawtypes")
        ServiceLoader<Chronology> loader = ServiceLoader.load(Chronology.class);
        for (Chronology chrono : loader) {
            if (type.equals(chrono.getCalendarType())) {
                return chrono;
            }
        }
        throw new DateTimeException("Unknown calendar system: " + type);
    }

    //-----------------------------------------------------------------------
    
Obtains an instance of Chronology from a chronology ID or calendar system type. 
 See Chronology.of(String). 
Params:
  • id –  the chronology ID or calendar system type, not null
Throws:
Returns:the chronology with the identifier requested, not null
/**
     * Obtains an instance of {@code Chronology} from a chronology ID or
     * calendar system type.
     * <p>
     * See {@link Chronology#of(String)}.
     *
     * @param id  the chronology ID or calendar system type, not null
     * @return the chronology with the identifier requested, not null
     * @throws java.time.DateTimeException if the chronology cannot be found
     */
    static Chronology of(String id) {
        Objects.requireNonNull(id, "id");
        do {
            Chronology chrono = of0(id);
            if (chrono != null) {
                return chrono;
            }
            // If not found, do the initialization (once) and repeat the lookup
        } while (initCache());

        // Look for a Chronology using ServiceLoader of the Thread's ContextClassLoader
        // Application provided Chronologies must not be cached
        @SuppressWarnings("rawtypes")
        ServiceLoader<Chronology> loader = ServiceLoader.load(Chronology.class);
        for (Chronology chrono : loader) {
            if (id.equals(chrono.getId()) || id.equals(chrono.getCalendarType())) {
                return chrono;
            }
        }
        throw new DateTimeException("Unknown chronology: " + id);
    }

    
Obtains an instance of Chronology from a chronology ID or calendar system type. 
Params:
  • id –  the chronology ID or calendar system type, not null
Returns:the chronology with the identifier requested, or null if not found
/**
     * Obtains an instance of {@code Chronology} from a chronology ID or
     * calendar system type.
     *
     * @param id  the chronology ID or calendar system type, not null
     * @return the chronology with the identifier requested, or {@code null} if not found
     */
    private static Chronology of0(String id) {
        Chronology chrono = CHRONOS_BY_ID.get(id);
        if (chrono == null) {
            chrono = CHRONOS_BY_TYPE.get(id);
        }
        return chrono;
    }

    
Returns the available chronologies.

 Each returned Chronology is available for use in the system. The set of chronologies includes the system chronologies and any chronologies provided by the application via ServiceLoader configuration. 
Returns:the independent, modifiable set of the available chronology IDs, not null
/**
     * Returns the available chronologies.
     * <p>
     * Each returned {@code Chronology} is available for use in the system.
     * The set of chronologies includes the system chronologies and
     * any chronologies provided by the application via ServiceLoader
     * configuration.
     *
     * @return the independent, modifiable set of the available chronology IDs, not null
     */
    static Set<Chronology> getAvailableChronologies() {
        initCache();       // force initialization
        HashSet<Chronology> chronos = new HashSet<>(CHRONOS_BY_ID.values());

        /// Add in Chronologies from the ServiceLoader configuration
        @SuppressWarnings("rawtypes")
        ServiceLoader<Chronology> loader = ServiceLoader.load(Chronology.class);
        for (Chronology chrono : loader) {
            chronos.add(chrono);
        }
        return chronos;
    }

    //-----------------------------------------------------------------------
    
Creates an instance.

/**
     * Creates an instance.
     */
    protected AbstractChronology() {
    }

    //-----------------------------------------------------------------------
    
Resolves parsed ChronoField values into a date during parsing. 
 Most TemporalField implementations are resolved using the resolve method on the field. By contrast, the ChronoField class defines fields that only have meaning relative to the chronology. As such, ChronoField date fields are resolved here in the context of a specific chronology. 
 ChronoField instances are resolved by this method, which may be overridden in subclasses. 
    

  • EPOCH_DAY - If present, this is converted to a date and all other date fields are then cross-checked against the date. 
  • PROLEPTIC_MONTH - If present, then it is split into the YEAR and MONTH_OF_YEAR. If the mode is strict or smart then the field is validated. 
  • YEAR_OF_ERA and ERA - If both are present, then they are combined to form a YEAR. In lenient mode, the YEAR_OF_ERA range is not validated, in smart and strict mode it is. The ERA is validated for range in all three modes. If only the YEAR_OF_ERA is present, and the mode is smart or lenient, then the last available era is assumed. In strict mode, no era is assumed and the YEAR_OF_ERA is left untouched. If only the ERA is present, then it is left untouched. 
  • YEAR, MONTH_OF_YEAR and DAY_OF_MONTH - If all three are present, then they are combined to form a date. In all three modes, the YEAR is validated. If the mode is smart or strict, then the month and day are validated. If the mode is lenient, then the date is combined in a manner equivalent to creating a date on the first day of the first month in the requested year, then adding the difference in months, then the difference in days. If the mode is smart, and the day-of-month is greater than the maximum for the year-month, then the day-of-month is adjusted to the last day-of-month. If the mode is strict, then the three fields must form a valid date. 
  • YEAR and DAY_OF_YEAR - If both are present, then they are combined to form a date. In all three modes, the YEAR is validated. If the mode is lenient, then the date is combined in a manner equivalent to creating a date on the first day of the requested year, then adding the difference in days. If the mode is smart or strict, then the two fields must form a valid date. 
  • YEAR, MONTH_OF_YEAR, ALIGNED_WEEK_OF_MONTH and ALIGNED_DAY_OF_WEEK_IN_MONTH - If all four are present, then they are combined to form a date. In all three modes, the YEAR is validated. If the mode is lenient, then the date is combined in a manner equivalent to creating a date on the first day of the first month in the requested year, then adding the difference in months, then the difference in weeks, then in days. If the mode is smart or strict, then the all four fields are validated to their outer ranges. The date is then combined in a manner equivalent to creating a date on the first day of the requested year and month, then adding the amount in weeks and days to reach their values. If the mode is strict, the date is additionally validated to check that the day and week adjustment did not change the month. 
  • YEAR, MONTH_OF_YEAR, ALIGNED_WEEK_OF_MONTH and DAY_OF_WEEK - If all four are present, then they are combined to form a date. The approach is the same as described above for years, months and weeks in ALIGNED_DAY_OF_WEEK_IN_MONTH. The day-of-week is adjusted as the next or same matching day-of-week once the years, months and weeks have been handled. 
  • YEAR, ALIGNED_WEEK_OF_YEAR and ALIGNED_DAY_OF_WEEK_IN_YEAR - If all three are present, then they are combined to form a date. In all three modes, the YEAR is validated. If the mode is lenient, then the date is combined in a manner equivalent to creating a date on the first day of the requested year, then adding the difference in weeks, then in days. If the mode is smart or strict, then the all three fields are validated to their outer ranges. The date is then combined in a manner equivalent to creating a date on the first day of the requested year, then adding the amount in weeks and days to reach their values. If the mode is strict, the date is additionally validated to check that the day and week adjustment did not change the year. 
  • YEAR, ALIGNED_WEEK_OF_YEAR and DAY_OF_WEEK - If all three are present, then they are combined to form a date. The approach is the same as described above for years and weeks in ALIGNED_DAY_OF_WEEK_IN_YEAR. The day-of-week is adjusted as the next or same matching day-of-week once the years and weeks have been handled. 


 The default implementation is suitable for most calendar systems. If ChronoField.YEAR_OF_ERA is found without an ChronoField.ERA then the last era in Chronology.eras() is used. The implementation assumes a 7 day week, that the first day-of-month has the value 1, that first day-of-year has the value 1, and that the first of the month and year always exists. 
Params:
  • fieldValues –  the map of fields to values, which can be updated, not null
  • resolverStyle –  the requested type of resolve, not null
Throws:
  • DateTimeException – if the date cannot be resolved, typically
 because of a conflict in the input data
Returns:the resolved date, null if insufficient information to create a date
/**
     * Resolves parsed {@code ChronoField} values into a date during parsing.
     * <p>
     * Most {@code TemporalField} implementations are resolved using the
     * resolve method on the field. By contrast, the {@code ChronoField} class
     * defines fields that only have meaning relative to the chronology.
     * As such, {@code ChronoField} date fields are resolved here in the
     * context of a specific chronology.
     * <p>
     * {@code ChronoField} instances are resolved by this method, which may
     * be overridden in subclasses.
     * <ul>
     * <li>{@code EPOCH_DAY} - If present, this is converted to a date and
     *  all other date fields are then cross-checked against the date.
     * <li>{@code PROLEPTIC_MONTH} - If present, then it is split into the
     *  {@code YEAR} and {@code MONTH_OF_YEAR}. If the mode is strict or smart
     *  then the field is validated.
     * <li>{@code YEAR_OF_ERA} and {@code ERA} - If both are present, then they
     *  are combined to form a {@code YEAR}. In lenient mode, the {@code YEAR_OF_ERA}
     *  range is not validated, in smart and strict mode it is. The {@code ERA} is
     *  validated for range in all three modes. If only the {@code YEAR_OF_ERA} is
     *  present, and the mode is smart or lenient, then the last available era
     *  is assumed. In strict mode, no era is assumed and the {@code YEAR_OF_ERA} is
     *  left untouched. If only the {@code ERA} is present, then it is left untouched.
     * <li>{@code YEAR}, {@code MONTH_OF_YEAR} and {@code DAY_OF_MONTH} -
     *  If all three are present, then they are combined to form a date.
     *  In all three modes, the {@code YEAR} is validated.
     *  If the mode is smart or strict, then the month and day are validated.
     *  If the mode is lenient, then the date is combined in a manner equivalent to
     *  creating a date on the first day of the first month in the requested year,
     *  then adding the difference in months, then the difference in days.
     *  If the mode is smart, and the day-of-month is greater than the maximum for
     *  the year-month, then the day-of-month is adjusted to the last day-of-month.
     *  If the mode is strict, then the three fields must form a valid date.
     * <li>{@code YEAR} and {@code DAY_OF_YEAR} -
     *  If both are present, then they are combined to form a date.
     *  In all three modes, the {@code YEAR} is validated.
     *  If the mode is lenient, then the date is combined in a manner equivalent to
     *  creating a date on the first day of the requested year, then adding
     *  the difference in days.
     *  If the mode is smart or strict, then the two fields must form a valid date.
     * <li>{@code YEAR}, {@code MONTH_OF_YEAR}, {@code ALIGNED_WEEK_OF_MONTH} and
     *  {@code ALIGNED_DAY_OF_WEEK_IN_MONTH} -
     *  If all four are present, then they are combined to form a date.
     *  In all three modes, the {@code YEAR} is validated.
     *  If the mode is lenient, then the date is combined in a manner equivalent to
     *  creating a date on the first day of the first month in the requested year, then adding
     *  the difference in months, then the difference in weeks, then in days.
     *  If the mode is smart or strict, then the all four fields are validated to
     *  their outer ranges. The date is then combined in a manner equivalent to
     *  creating a date on the first day of the requested year and month, then adding
     *  the amount in weeks and days to reach their values. If the mode is strict,
     *  the date is additionally validated to check that the day and week adjustment
     *  did not change the month.
     * <li>{@code YEAR}, {@code MONTH_OF_YEAR}, {@code ALIGNED_WEEK_OF_MONTH} and
     *  {@code DAY_OF_WEEK} - If all four are present, then they are combined to
     *  form a date. The approach is the same as described above for
     *  years, months and weeks in {@code ALIGNED_DAY_OF_WEEK_IN_MONTH}.
     *  The day-of-week is adjusted as the next or same matching day-of-week once
     *  the years, months and weeks have been handled.
     * <li>{@code YEAR}, {@code ALIGNED_WEEK_OF_YEAR} and {@code ALIGNED_DAY_OF_WEEK_IN_YEAR} -
     *  If all three are present, then they are combined to form a date.
     *  In all three modes, the {@code YEAR} is validated.
     *  If the mode is lenient, then the date is combined in a manner equivalent to
     *  creating a date on the first day of the requested year, then adding
     *  the difference in weeks, then in days.
     *  If the mode is smart or strict, then the all three fields are validated to
     *  their outer ranges. The date is then combined in a manner equivalent to
     *  creating a date on the first day of the requested year, then adding
     *  the amount in weeks and days to reach their values. If the mode is strict,
     *  the date is additionally validated to check that the day and week adjustment
     *  did not change the year.
     * <li>{@code YEAR}, {@code ALIGNED_WEEK_OF_YEAR} and {@code DAY_OF_WEEK} -
     *  If all three are present, then they are combined to form a date.
     *  The approach is the same as described above for years and weeks in
     *  {@code ALIGNED_DAY_OF_WEEK_IN_YEAR}. The day-of-week is adjusted as the
     *  next or same matching day-of-week once the years and weeks have been handled.
     * </ul>
     * <p>
     * The default implementation is suitable for most calendar systems.
     * If {@link java.time.temporal.ChronoField#YEAR_OF_ERA} is found without an {@link java.time.temporal.ChronoField#ERA}
     * then the last era in {@link #eras()} is used.
     * The implementation assumes a 7 day week, that the first day-of-month
     * has the value 1, that first day-of-year has the value 1, and that the
     * first of the month and year always exists.
     *
     * @param fieldValues  the map of fields to values, which can be updated, not null
     * @param resolverStyle  the requested type of resolve, not null
     * @return the resolved date, null if insufficient information to create a date
     * @throws java.time.DateTimeException if the date cannot be resolved, typically
     *  because of a conflict in the input data
     */
    @Override
    public ChronoLocalDate resolveDate(Map<TemporalField, Long> fieldValues, ResolverStyle resolverStyle) {
        // check epoch-day before inventing era
        if (fieldValues.containsKey(EPOCH_DAY)) {
            return dateEpochDay(fieldValues.remove(EPOCH_DAY));
        }

        // fix proleptic month before inventing era
        resolveProlepticMonth(fieldValues, resolverStyle);

        // invent era if necessary to resolve year-of-era
        ChronoLocalDate resolved = resolveYearOfEra(fieldValues, resolverStyle);
        if (resolved != null) {
            return resolved;
        }

        // build date
        if (fieldValues.containsKey(YEAR)) {
            if (fieldValues.containsKey(MONTH_OF_YEAR)) {
                if (fieldValues.containsKey(DAY_OF_MONTH)) {
                    return resolveYMD(fieldValues, resolverStyle);
                }
                if (fieldValues.containsKey(ALIGNED_WEEK_OF_MONTH)) {
                    if (fieldValues.containsKey(ALIGNED_DAY_OF_WEEK_IN_MONTH)) {
                        return resolveYMAA(fieldValues, resolverStyle);
                    }
                    if (fieldValues.containsKey(DAY_OF_WEEK)) {
                        return resolveYMAD(fieldValues, resolverStyle);
                    }
                }
            }
            if (fieldValues.containsKey(DAY_OF_YEAR)) {
                return resolveYD(fieldValues, resolverStyle);
            }
            if (fieldValues.containsKey(ALIGNED_WEEK_OF_YEAR)) {
                if (fieldValues.containsKey(ALIGNED_DAY_OF_WEEK_IN_YEAR)) {
                    return resolveYAA(fieldValues, resolverStyle);
                }
                if (fieldValues.containsKey(DAY_OF_WEEK)) {
                    return resolveYAD(fieldValues, resolverStyle);
                }
            }
        }
        return null;
    }

    void resolveProlepticMonth(Map<TemporalField, Long> fieldValues, ResolverStyle resolverStyle) {
        Long pMonth = fieldValues.remove(PROLEPTIC_MONTH);
        if (pMonth != null) {
            if (resolverStyle != ResolverStyle.LENIENT) {
                PROLEPTIC_MONTH.checkValidValue(pMonth);
            }
            // first day-of-month is likely to be safest for setting proleptic-month
            // cannot add to year zero, as not all chronologies have a year zero
            ChronoLocalDate chronoDate = dateNow()
                    .with(DAY_OF_MONTH, 1).with(PROLEPTIC_MONTH, pMonth);
            addFieldValue(fieldValues, MONTH_OF_YEAR, chronoDate.get(MONTH_OF_YEAR));
            addFieldValue(fieldValues, YEAR, chronoDate.get(YEAR));
        }
    }

    ChronoLocalDate resolveYearOfEra(Map<TemporalField, Long> fieldValues, ResolverStyle resolverStyle) {
        Long yoeLong = fieldValues.remove(YEAR_OF_ERA);
        if (yoeLong != null) {
            Long eraLong = fieldValues.remove(ERA);
            int yoe;
            if (resolverStyle != ResolverStyle.LENIENT) {
                yoe = range(YEAR_OF_ERA).checkValidIntValue(yoeLong, YEAR_OF_ERA);
            } else {
                yoe = Math.toIntExact(yoeLong);
            }
            if (eraLong != null) {
                Era eraObj = eraOf(range(ERA).checkValidIntValue(eraLong, ERA));
                addFieldValue(fieldValues, YEAR, prolepticYear(eraObj, yoe));
            } else {
                if (fieldValues.containsKey(YEAR)) {
                    int year = range(YEAR).checkValidIntValue(fieldValues.get(YEAR), YEAR);
                    ChronoLocalDate chronoDate = dateYearDay(year, 1);
                    addFieldValue(fieldValues, YEAR, prolepticYear(chronoDate.getEra(), yoe));
                } else if (resolverStyle == ResolverStyle.STRICT) {
                    // do not invent era if strict
                    // reinstate the field removed earlier, no cross-check issues
                    fieldValues.put(YEAR_OF_ERA, yoeLong);
                } else {
                    List<Era> eras = eras();
                    if (eras.isEmpty()) {
                        addFieldValue(fieldValues, YEAR, yoe);
                    } else {
                        Era eraObj = eras.get(eras.size() - 1);
                        addFieldValue(fieldValues, YEAR, prolepticYear(eraObj, yoe));
                    }
                }
            }
        } else if (fieldValues.containsKey(ERA)) {
            range(ERA).checkValidValue(fieldValues.get(ERA), ERA);  // always validated
        }
        return null;
    }

    ChronoLocalDate resolveYMD(Map<TemporalField, Long> fieldValues, ResolverStyle resolverStyle) {
        int y = range(YEAR).checkValidIntValue(fieldValues.remove(YEAR), YEAR);
        if (resolverStyle == ResolverStyle.LENIENT) {
            long months = Math.subtractExact(fieldValues.remove(MONTH_OF_YEAR), 1);
            long days = Math.subtractExact(fieldValues.remove(DAY_OF_MONTH), 1);
            return date(y, 1, 1).plus(months, MONTHS).plus(days, DAYS);
        }
        int moy = range(MONTH_OF_YEAR).checkValidIntValue(fieldValues.remove(MONTH_OF_YEAR), MONTH_OF_YEAR);
        ValueRange domRange = range(DAY_OF_MONTH);
        int dom = domRange.checkValidIntValue(fieldValues.remove(DAY_OF_MONTH), DAY_OF_MONTH);
        if (resolverStyle == ResolverStyle.SMART) {  // previous valid
            try {
                return date(y, moy, dom);
            } catch (DateTimeException ex) {
                return date(y, moy, 1).with(TemporalAdjusters.lastDayOfMonth());
            }
        }
        return date(y, moy, dom);
    }

    ChronoLocalDate resolveYD(Map<TemporalField, Long> fieldValues, ResolverStyle resolverStyle) {
        int y = range(YEAR).checkValidIntValue(fieldValues.remove(YEAR), YEAR);
        if (resolverStyle == ResolverStyle.LENIENT) {
            long days = Math.subtractExact(fieldValues.remove(DAY_OF_YEAR), 1);
            return dateYearDay(y, 1).plus(days, DAYS);
        }
        int doy = range(DAY_OF_YEAR).checkValidIntValue(fieldValues.remove(DAY_OF_YEAR), DAY_OF_YEAR);
        return dateYearDay(y, doy);  // smart is same as strict
    }

    ChronoLocalDate resolveYMAA(Map<TemporalField, Long> fieldValues, ResolverStyle resolverStyle) {
        int y = range(YEAR).checkValidIntValue(fieldValues.remove(YEAR), YEAR);
        if (resolverStyle == ResolverStyle.LENIENT) {
            long months = Math.subtractExact(fieldValues.remove(MONTH_OF_YEAR), 1);
            long weeks = Math.subtractExact(fieldValues.remove(ALIGNED_WEEK_OF_MONTH), 1);
            long days = Math.subtractExact(fieldValues.remove(ALIGNED_DAY_OF_WEEK_IN_MONTH), 1);
            return date(y, 1, 1).plus(months, MONTHS).plus(weeks, WEEKS).plus(days, DAYS);
        }
        int moy = range(MONTH_OF_YEAR).checkValidIntValue(fieldValues.remove(MONTH_OF_YEAR), MONTH_OF_YEAR);
        int aw = range(ALIGNED_WEEK_OF_MONTH).checkValidIntValue(fieldValues.remove(ALIGNED_WEEK_OF_MONTH), ALIGNED_WEEK_OF_MONTH);
        int ad = range(ALIGNED_DAY_OF_WEEK_IN_MONTH).checkValidIntValue(fieldValues.remove(ALIGNED_DAY_OF_WEEK_IN_MONTH), ALIGNED_DAY_OF_WEEK_IN_MONTH);
        ChronoLocalDate date = date(y, moy, 1).plus((aw - 1) * 7 + (ad - 1), DAYS);
        if (resolverStyle == ResolverStyle.STRICT && date.get(MONTH_OF_YEAR) != moy) {
            throw new DateTimeException("Strict mode rejected resolved date as it is in a different month");
        }
        return date;
    }

    ChronoLocalDate resolveYMAD(Map<TemporalField, Long> fieldValues, ResolverStyle resolverStyle) {
        int y = range(YEAR).checkValidIntValue(fieldValues.remove(YEAR), YEAR);
        if (resolverStyle == ResolverStyle.LENIENT) {
            long months = Math.subtractExact(fieldValues.remove(MONTH_OF_YEAR), 1);
            long weeks = Math.subtractExact(fieldValues.remove(ALIGNED_WEEK_OF_MONTH), 1);
            long dow = Math.subtractExact(fieldValues.remove(DAY_OF_WEEK), 1);
            return resolveAligned(date(y, 1, 1), months, weeks, dow);
        }
        int moy = range(MONTH_OF_YEAR).checkValidIntValue(fieldValues.remove(MONTH_OF_YEAR), MONTH_OF_YEAR);
        int aw = range(ALIGNED_WEEK_OF_MONTH).checkValidIntValue(fieldValues.remove(ALIGNED_WEEK_OF_MONTH), ALIGNED_WEEK_OF_MONTH);
        int dow = range(DAY_OF_WEEK).checkValidIntValue(fieldValues.remove(DAY_OF_WEEK), DAY_OF_WEEK);
        ChronoLocalDate date = date(y, moy, 1).plus((aw - 1) * 7, DAYS).with(nextOrSame(DayOfWeek.of(dow)));
        if (resolverStyle == ResolverStyle.STRICT && date.get(MONTH_OF_YEAR) != moy) {
            throw new DateTimeException("Strict mode rejected resolved date as it is in a different month");
        }
        return date;
    }

    ChronoLocalDate resolveYAA(Map<TemporalField, Long> fieldValues, ResolverStyle resolverStyle) {
        int y = range(YEAR).checkValidIntValue(fieldValues.remove(YEAR), YEAR);
        if (resolverStyle == ResolverStyle.LENIENT) {
            long weeks = Math.subtractExact(fieldValues.remove(ALIGNED_WEEK_OF_YEAR), 1);
            long days = Math.subtractExact(fieldValues.remove(ALIGNED_DAY_OF_WEEK_IN_YEAR), 1);
            return dateYearDay(y, 1).plus(weeks, WEEKS).plus(days, DAYS);
        }
        int aw = range(ALIGNED_WEEK_OF_YEAR).checkValidIntValue(fieldValues.remove(ALIGNED_WEEK_OF_YEAR), ALIGNED_WEEK_OF_YEAR);
        int ad = range(ALIGNED_DAY_OF_WEEK_IN_YEAR).checkValidIntValue(fieldValues.remove(ALIGNED_DAY_OF_WEEK_IN_YEAR), ALIGNED_DAY_OF_WEEK_IN_YEAR);
        ChronoLocalDate date = dateYearDay(y, 1).plus((aw - 1) * 7 + (ad - 1), DAYS);
        if (resolverStyle == ResolverStyle.STRICT && date.get(YEAR) != y) {
            throw new DateTimeException("Strict mode rejected resolved date as it is in a different year");
        }
        return date;
    }

    ChronoLocalDate resolveYAD(Map<TemporalField, Long> fieldValues, ResolverStyle resolverStyle) {
        int y = range(YEAR).checkValidIntValue(fieldValues.remove(YEAR), YEAR);
        if (resolverStyle == ResolverStyle.LENIENT) {
            long weeks = Math.subtractExact(fieldValues.remove(ALIGNED_WEEK_OF_YEAR), 1);
            long dow = Math.subtractExact(fieldValues.remove(DAY_OF_WEEK), 1);
            return resolveAligned(dateYearDay(y, 1), 0, weeks, dow);
        }
        int aw = range(ALIGNED_WEEK_OF_YEAR).checkValidIntValue(fieldValues.remove(ALIGNED_WEEK_OF_YEAR), ALIGNED_WEEK_OF_YEAR);
        int dow = range(DAY_OF_WEEK).checkValidIntValue(fieldValues.remove(DAY_OF_WEEK), DAY_OF_WEEK);
        ChronoLocalDate date = dateYearDay(y, 1).plus((aw - 1) * 7, DAYS).with(nextOrSame(DayOfWeek.of(dow)));
        if (resolverStyle == ResolverStyle.STRICT && date.get(YEAR) != y) {
            throw new DateTimeException("Strict mode rejected resolved date as it is in a different year");
        }
        return date;
    }

    ChronoLocalDate resolveAligned(ChronoLocalDate base, long months, long weeks, long dow) {
        ChronoLocalDate date = base.plus(months, MONTHS).plus(weeks, WEEKS);
        if (dow > 7) {
            date = date.plus((dow - 1) / 7, WEEKS);
            dow = ((dow - 1) % 7) + 1;
        } else if (dow < 1) {
            date = date.plus(Math.subtractExact(dow,  7) / 7, WEEKS);
            dow = ((dow + 6) % 7) + 1;
        }
        return date.with(nextOrSame(DayOfWeek.of((int) dow)));
    }

    
Adds a field-value pair to the map, checking for conflicts.


If the field is not already present, then the field-value pair is added to the map.
If the field is already present and it has the same value as that specified, no action occurs.
If the field is already present and it has a different value to that specified, then
an exception is thrown.

Params:
  • field –  the field to add, not null
  • value –  the value to add, not null
Throws:
/**
     * Adds a field-value pair to the map, checking for conflicts.
     * <p>
     * If the field is not already present, then the field-value pair is added to the map.
     * If the field is already present and it has the same value as that specified, no action occurs.
     * If the field is already present and it has a different value to that specified, then
     * an exception is thrown.
     *
     * @param field  the field to add, not null
     * @param value  the value to add, not null
     * @throws java.time.DateTimeException if the field is already present with a different value
     */
    void addFieldValue(Map<TemporalField, Long> fieldValues, ChronoField field, long value) {
        Long old = fieldValues.get(field);  // check first for better error message
        if (old != null && old.longValue() != value) {
            throw new DateTimeException("Conflict found: " + field + " " + old + " differs from " + field + " " + value);
        }
        fieldValues.put(field, value);
    }

    //-----------------------------------------------------------------------
    
Compares this chronology to another chronology.

 The comparison order first by the chronology ID string, then by any additional information specific to the subclass. It is "consistent with equals", as defined by Comparable. 
Params:
  • other –  the other chronology to compare to, not null
Implementation Requirements:
This implementation compares the chronology ID.
Subclasses must compare any additional state that they store.
Returns:the comparator value, negative if less, positive if greater
/**
     * Compares this chronology to another chronology.
     * <p>
     * The comparison order first by the chronology ID string, then by any
     * additional information specific to the subclass.
     * It is "consistent with equals", as defined by {@link Comparable}.
     *
     * @implSpec
     * This implementation compares the chronology ID.
     * Subclasses must compare any additional state that they store.
     *
     * @param other  the other chronology to compare to, not null
     * @return the comparator value, negative if less, positive if greater
     */
    @Override
    public int compareTo(Chronology other) {
        return getId().compareTo(other.getId());
    }

    
Checks if this chronology is equal to another chronology.


The comparison is based on the entire state of the object.

Params:
  • obj –  the object to check, null returns false
Implementation Requirements: This implementation checks the type and calls compareTo(Chronology).
Returns:true if this is equal to the other chronology
/**
     * Checks if this chronology is equal to another chronology.
     * <p>
     * The comparison is based on the entire state of the object.
     *
     * @implSpec
     * This implementation checks the type and calls
     * {@link #compareTo(java.time.chrono.Chronology)}.
     *
     * @param obj  the object to check, null returns false
     * @return true if this is equal to the other chronology
     */
    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
           return true;
        }
        if (obj instanceof AbstractChronology) {
            return compareTo((AbstractChronology) obj) == 0;
        }
        return false;
    }

    
A hash code for this chronology.


The hash code should be based on the entire state of the object.

Implementation Requirements:
This implementation is based on the chronology ID and class.
Subclasses should add any additional state that they store.
Returns:a suitable hash code
/**
     * A hash code for this chronology.
     * <p>
     * The hash code should be based on the entire state of the object.
     *
     * @implSpec
     * This implementation is based on the chronology ID and class.
     * Subclasses should add any additional state that they store.
     *
     * @return a suitable hash code
     */
    @Override
    public int hashCode() {
        return getClass().hashCode() ^ getId().hashCode();
    }

    //-----------------------------------------------------------------------
    
Outputs this chronology as a String, using the chronology ID. 
Returns:a string representation of this chronology, not null
/**
     * Outputs this chronology as a {@code String}, using the chronology ID.
     *
     * @return a string representation of this chronology, not null
     */
    @Override
    public String toString() {
        return getId();
    }

    //-----------------------------------------------------------------------
    
Writes the Chronology using a
dedicated serialized form.

 out.writeByte(1);  // identifies this as a Chronology
 out.writeUTF(getId());



Returns:the instance of Ser, not null
/**
     * Writes the Chronology using a
     * <a href="../../../serialized-form.html#java.time.chrono.Ser">dedicated serialized form</a>.
     * <pre>
     *  out.writeByte(1);  // identifies this as a Chronology
     *  out.writeUTF(getId());
     * </pre>
     *
     * @return the instance of {@code Ser}, not null
     */
    Object writeReplace() {
        return new Ser(Ser.CHRONO_TYPE, this);
    }

    
Defend against malicious streams.

Params:
  • s – the stream to read
Throws:
/**
     * Defend against malicious streams.
     *
     * @param s the stream to read
     * @throws java.io.InvalidObjectException always
     */
    private void readObject(ObjectInputStream s) throws ObjectStreamException {
        throw new InvalidObjectException("Deserialization via serialization delegate");
    }

    void writeExternal(DataOutput out) throws IOException {
        out.writeUTF(getId());
    }

    static Chronology readExternal(DataInput in) throws IOException {
        String id = in.readUTF();
        return Chronology.of(id);
    }

}