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

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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 java.io.DataOutput;

import java.io.IOException;

import java.io.Serializable;

import java.time.format.DateTimeFormatterBuilder;

import java.time.format.TextStyle;

import java.time.temporal.TemporalAccessor;

import java.time.temporal.TemporalField;

import java.time.temporal.TemporalQuery;

import java.time.temporal.UnsupportedTemporalTypeException;

import java.time.zone.ZoneRules;

import java.time.zone.ZoneRulesException;

import java.time.zone.ZoneRulesProvider;

import java.util.Collections;

import java.util.HashMap;

import java.util.Locale;

import java.util.Map;

import java.util.Objects;

import java.util.Set;

import java.util.TimeZone;

/**

 * A time-zone ID, such as {@code Europe/Paris}.

 * <p>

 * A {@code ZoneId} is used to identify the rules used to convert between

 * an {@link Instant} and a {@link LocalDateTime}.

 * There are two distinct types of ID:

 * <p><ul>

 * <li>Fixed offsets - a fully resolved offset from UTC/Greenwich, that uses

 *  the same offset for all local date-times

 * <li>Geographical regions - an area where a specific set of rules for finding

 *  the offset from UTC/Greenwich apply

 * </ul><p>

 * Most fixed offsets are represented by {@link ZoneOffset}.

 * Calling {@link #normalized()} on any {@code ZoneId} will ensure that a

 * fixed offset ID will be represented as a {@code ZoneOffset}.

 * <p>

 * The actual rules, describing when and how the offset changes, are defined by {@link ZoneRules}.

 * This class is simply an ID used to obtain the underlying rules.

 * This approach is taken because rules are defined by governments and change

 * frequently, whereas the ID is stable.

 * <p>

 * The distinction has other effects. Serializing the {@code ZoneId} will only send

 * the ID, whereas serializing the rules sends the entire data set.

 * Similarly, a comparison of two IDs only examines the ID, whereas

 * a comparison of two rules examines the entire data set.

 *

 * <h3>Time-zone IDs</h3>

 * The ID is unique within the system.

 * There are three types of ID.

 * <p>

 * The simplest type of ID is that from {@code ZoneOffset}.

 * This consists of 'Z' and IDs starting with '+' or '-'.

 * <p>

 * The next type of ID are offset-style IDs with some form of prefix,

 * such as 'GMT+2' or 'UTC+01:00'.

 * The recognised prefixes are 'UTC', 'GMT' and 'UT'.

 * The offset is the suffix and will be normalized during creation.

 * These IDs can be normalized to a {@code ZoneOffset} using {@code normalized()}.

 * <p>

 * The third type of ID are region-based IDs. A region-based ID must be of

 * two or more characters, and not start with 'UTC', 'GMT', 'UT' '+' or '-'.

 * Region-based IDs are defined by configuration, see {@link ZoneRulesProvider}.

 * The configuration focuses on providing the lookup from the ID to the

 * underlying {@code ZoneRules}.

 * <p>

 * Time-zone rules are defined by governments and change frequently.

 * There are a number of organizations, known here as groups, that monitor

 * time-zone changes and collate them.

 * The default group is the IANA Time Zone Database (TZDB).

 * Other organizations include IATA (the airline industry body) and Microsoft.

 * <p>

 * Each group defines its own format for the region ID it provides.

 * The TZDB group defines IDs such as 'Europe/London' or 'America/New_York'.

 * TZDB IDs take precedence over other groups.

 * <p>

 * It is strongly recommended that the group name is included in all IDs supplied by

 * groups other than TZDB to avoid conflicts. For example, IATA airline time-zone

 * region IDs are typically the same as the three letter airport code.

 * However, the airport of Utrecht has the code 'UTC', which is obviously a conflict.

 * The recommended format for region IDs from groups other than TZDB is 'group~region'.

 * Thus if IATA data were defined, Utrecht airport would be 'IATA~UTC'.

 *

 * <h3>Serialization</h3>

 * This class can be serialized and stores the string zone ID in the external form.

 * The {@code ZoneOffset} subclass uses a dedicated format that only stores the

 * offset from UTC/Greenwich.

 * <p>

 * A {@code ZoneId} can be deserialized in a Java Runtime where the ID is unknown.

 * For example, if a server-side Java Runtime has been updated with a new zone ID, but

 * the client-side Java Runtime has not been updated. In this case, the {@code ZoneId}

 * object will exist, and can be queried using {@code getId}, {@code equals},

 * {@code hashCode}, {@code toString}, {@code getDisplayName} and {@code normalized}.

 * However, any call to {@code getRules} will fail with {@code ZoneRulesException}.

 * This approach is designed to allow a {@link ZonedDateTime} to be loaded and

 * queried, but not modified, on a Java Runtime with incomplete time-zone information.

 *

 * @implSpec

 * This abstract class has two implementations, both of which are immutable and thread-safe.

 * One implementation models region-based IDs, the other is {@code ZoneOffset} modelling

 * offset-based IDs. This difference is visible in serialization.

 *

 * @since 1.8

 */

public abstract class ZoneId implements Serializable {

    /**

     * A map of zone overrides to enable the older short time-zone names to be used.

     * <p>

     * Use of short zone IDs has been deprecated in {@code java.util.TimeZone}.

     * This map allows the IDs to continue to be used via the

     * {@link #of(String, Map)} factory method.

     * <p>

     * This map contains an older mapping of the IDs, where 'EST', 'MST' and 'HST'

     * map to IDs which include daylight savings.

     * This is in line with versions of TZDB before 2005r.

     * <p>

     * This maps as follows:

     * <p><ul>

     * <li>EST - America/New_York</li>

     * <li>MST - America/Denver</li>

     * <li>HST - Pacific/Honolulu</li>

     * <li>ACT - Australia/Darwin</li>

     * <li>AET - Australia/Sydney</li>

     * <li>AGT - America/Argentina/Buenos_Aires</li>

     * <li>ART - Africa/Cairo</li>

     * <li>AST - America/Anchorage</li>

     * <li>BET - America/Sao_Paulo</li>

     * <li>BST - Asia/Dhaka</li>

     * <li>CAT - Africa/Harare</li>

     * <li>CNT - America/St_Johns</li>

     * <li>CST - America/Chicago</li>

     * <li>CTT - Asia/Shanghai</li>

     * <li>EAT - Africa/Addis_Ababa</li>

     * <li>ECT - Europe/Paris</li>

     * <li>IET - America/Indiana/Indianapolis</li>

     * <li>IST - Asia/Kolkata</li>

     * <li>JST - Asia/Tokyo</li>

     * <li>MIT - Pacific/Apia</li>

     * <li>NET - Asia/Yerevan</li>

     * <li>NST - Pacific/Auckland</li>

     * <li>PLT - Asia/Karachi</li>

     * <li>PNT - America/Phoenix</li>

     * <li>PRT - America/Puerto_Rico</li>

     * <li>PST - America/Los_Angeles</li>

     * <li>SST - Pacific/Guadalcanal</li>

     * <li>VST - Asia/Ho_Chi_Minh</li>

     * </ul><p>

     * The map is unmodifiable.

     */

    public static final Map<String, String> OLD_SHORT_IDS;

    /**

     * A map of zone overrides to enable the short time-zone names to be used.

     * <p>

     * Use of short zone IDs has been deprecated in {@code java.util.TimeZone}.

     * This map allows the IDs to continue to be used via the

     * {@link #of(String, Map)} factory method.

     * <p>

     * This map contains a newer mapping of the IDs, where 'EST', 'MST' and 'HST'

     * map to IDs which do not include daylight savings

     * This is in line with TZDB 2005r and later.

     * <p>

     * This maps as follows:

     * <p><ul>

     * <li>EST - -05:00</li>

     * <li>HST - -10:00</li>

     * <li>MST - -07:00</li>

     * <li>ACT - Australia/Darwin</li>

     * <li>AET - Australia/Sydney</li>

     * <li>AGT - America/Argentina/Buenos_Aires</li>

     * <li>ART - Africa/Cairo</li>

     * <li>AST - America/Anchorage</li>

     * <li>BET - America/Sao_Paulo</li>

     * <li>BST - Asia/Dhaka</li>

     * <li>CAT - Africa/Harare</li>

     * <li>CNT - America/St_Johns</li>

     * <li>CST - America/Chicago</li>

     * <li>CTT - Asia/Shanghai</li>

     * <li>EAT - Africa/Addis_Ababa</li>

     * <li>ECT - Europe/Paris</li>

     * <li>IET - America/Indiana/Indianapolis</li>

     * <li>IST - Asia/Kolkata</li>

     * <li>JST - Asia/Tokyo</li>

     * <li>MIT - Pacific/Apia</li>

     * <li>NET - Asia/Yerevan</li>

     * <li>NST - Pacific/Auckland</li>

     * <li>PLT - Asia/Karachi</li>

     * <li>PNT - America/Phoenix</li>

     * <li>PRT - America/Puerto_Rico</li>

     * <li>PST - America/Los_Angeles</li>

     * <li>SST - Pacific/Guadalcanal</li>

     * <li>VST - Asia/Ho_Chi_Minh</li>

     * </ul><p>

     * The map is unmodifiable.

     */

    public static final Map<String, String> SHORT_IDS;

    static {

        Map<String, String> base = new HashMap<>();

        base.put("ACT", "Australia/Darwin");

        base.put("AET", "Australia/Sydney");

        base.put("AGT", "America/Argentina/Buenos_Aires");

        base.put("ART", "Africa/Cairo");

        base.put("AST", "America/Anchorage");

        base.put("BET", "America/Sao_Paulo");

        base.put("BST", "Asia/Dhaka");

        base.put("CAT", "Africa/Harare");

        base.put("CNT", "America/St_Johns");

        base.put("CST", "America/Chicago");

        base.put("CTT", "Asia/Shanghai");

        base.put("EAT", "Africa/Addis_Ababa");

        base.put("ECT", "Europe/Paris");

        base.put("IET", "America/Indiana/Indianapolis");

        base.put("IST", "Asia/Kolkata");

        base.put("JST", "Asia/Tokyo");

        base.put("MIT", "Pacific/Apia");

        base.put("NET", "Asia/Yerevan");

        base.put("NST", "Pacific/Auckland");

        base.put("PLT", "Asia/Karachi");

        base.put("PNT", "America/Phoenix");

        base.put("PRT", "America/Puerto_Rico");

        base.put("PST", "America/Los_Angeles");

        base.put("SST", "Pacific/Guadalcanal");

        base.put("VST", "Asia/Ho_Chi_Minh");

        Map<String, String> pre = new HashMap<>(base);

        pre.put("EST", "America/New_York");

        pre.put("MST", "America/Denver");

        pre.put("HST", "Pacific/Honolulu");

        OLD_SHORT_IDS = Collections.unmodifiableMap(pre);

        Map<String, String> post = new HashMap<>(base);

        post.put("EST", "-05:00");

        post.put("MST", "-07:00");

        post.put("HST", "-10:00");

        SHORT_IDS = Collections.unmodifiableMap(post);

    }

    /**

     * Serialization version.

     */

    private static final long serialVersionUID = 8352817235686L;

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

    /**

     * Gets the system default time-zone.

     * <p>

     * This queries {@link TimeZone#getDefault()} to find the default time-zone

     * and converts it to a {@code ZoneId}. If the system default time-zone is changed,

     * then the result of this method will also change.

     *

     * @return the zone ID, not null

     * @throws DateTimeException if the converted zone ID has an invalid format

     * @throws ZoneRulesException if the converted zone region ID cannot be found

     */

    public static ZoneId systemDefault() {

        return ZoneId.of(TimeZone.getDefault().getID(), SHORT_IDS);

    }

    /**

     * Gets the set of available zone IDs.

     * <p>

     * This set includes the string form of all available region-based IDs.

     * Offset-based zone IDs are not included in the returned set.

     * The ID can be passed to {@link #of(String)} to create a {@code ZoneId}.

     * <p>

     * The set of zone IDs can increase over time, although in a typical application

     * the set of IDs is fixed. Each call to this method is thread-safe.

     *

     * @return a modifiable copy of the set of zone IDs, not null

     */

    public static Set<String> getAvailableZoneIds() {

        return ZoneRulesProvider.getAvailableZoneIds();

    }

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

    /**

     * Obtains an instance of {@code ZoneId} using its ID using a map

     * of aliases to supplement the standard zone IDs.

     * <p>

     * Many users of time-zones use short abbreviations, such as PST for

     * 'Pacific Standard Time' and PDT for 'Pacific Daylight Time'.

     * These abbreviations are not unique, and so cannot be used as IDs.

     * This method allows a map of string to time-zone to be setup and reused

     * within an application.

     *

     * @param zoneId  the time-zone ID, not null

     * @param aliasMap  a map of alias zone IDs (typically abbreviations) to real zone IDs, not null

     * @return the zone ID, not null

     * @throws DateTimeException if the zone ID has an invalid format

     * @throws ZoneRulesException if the zone ID is a region ID that cannot be found

     */

    public static ZoneId of(String zoneId, Map<String, String> aliasMap) {

        Objects.requireNonNull(zoneId, "zoneId");

        Objects.requireNonNull(aliasMap, "aliasMap");

        String id = aliasMap.get(zoneId);

        id = (id != null ? id : zoneId);

        return of(id);

    }

    /**

     * Obtains an instance of {@code ZoneId} from an ID ensuring that the

     * ID is valid and available for use.

     * <p>

     * This method parses the ID producing a {@code ZoneId} or {@code ZoneOffset}.

     * A {@code ZoneOffset} is returned if the ID is 'Z', or starts with '+' or '-'.

     * The result will always be a valid ID for which {@link ZoneRules} can be obtained.

     * <p>

     * Parsing matches the zone ID step by step as follows.

     * <ul>

     * <li>If the zone ID equals 'Z', the result is {@code ZoneOffset.UTC}.

     * <li>If the zone ID consists of a single letter, the zone ID is invalid

     *  and {@code DateTimeException} is thrown.

     * <li>If the zone ID starts with '+' or '-', the ID is parsed as a

     *  {@code ZoneOffset} using {@link ZoneOffset#of(String)}.

     * <li>If the zone ID equals 'GMT', 'UTC' or 'UT' then the result is a {@code ZoneId}

     *  with the same ID and rules equivalent to {@code ZoneOffset.UTC}.

     * <li>If the zone ID starts with 'UTC+', 'UTC-', 'GMT+', 'GMT-', 'UT+' or 'UT-'

     *  then the ID is a prefixed offset-based ID. The ID is split in two, with

     *  a two or three letter prefix and a suffix starting with the sign.

     *  The suffix is parsed as a {@link ZoneOffset#of(String) ZoneOffset}.

     *  The result will be a {@code ZoneId} with the specified UTC/GMT/UT prefix

     *  and the normalized offset ID as per {@link ZoneOffset#getId()}.

     *  The rules of the returned {@code ZoneId} will be equivalent to the

     *  parsed {@code ZoneOffset}.

     * <li>All other IDs are parsed as region-based zone IDs. Region IDs must

     *  match the regular expression <code>[A-Za-z][A-Za-z0-9~/._+-]+</code>

     *  otherwise a {@code DateTimeException} is thrown. If the zone ID is not

     *  in the configured set of IDs, {@code ZoneRulesException} is thrown.

     *  The detailed format of the region ID depends on the group supplying the data.

     *  The default set of data is supplied by the IANA Time Zone Database (TZDB).

     *  This has region IDs of the form '{area}/{city}', such as 'Europe/Paris' or 'America/New_York'.

     *  This is compatible with most IDs from {@link java.util.TimeZone}.

     * </ul>

     *

     * @param zoneId  the time-zone ID, not null

     * @return the zone ID, not null

     * @throws DateTimeException if the zone ID has an invalid format

     * @throws ZoneRulesException if the zone ID is a region ID that cannot be found

     */

    public static ZoneId of(String zoneId) {

        return of(zoneId, true);

    }

    /**

     * Obtains an instance of {@code ZoneId} wrapping an offset.

     * <p>

     * If the prefix is "GMT", "UTC", or "UT" a {@code ZoneId}

     * with the prefix and the non-zero offset is returned.

     * If the prefix is empty {@code ""} the {@code ZoneOffset} is returned.

     *

     * @param prefix  the time-zone ID, not null

     * @param offset  the offset, not null

     * @return the zone ID, not null

     * @throws IllegalArgumentException if the prefix is not one of

     *     "GMT", "UTC", or "UT", or ""

     */

    public static ZoneId ofOffset(String prefix, ZoneOffset offset) {

        Objects.requireNonNull(prefix, "prefix");

        Objects.requireNonNull(offset, "offset");

        if (prefix.length() == 0) {

            return offset;

        }

        if (!prefix.equals("GMT") && !prefix.equals("UTC") && !prefix.equals("UT")) {

             throw new IllegalArgumentException("prefix should be GMT, UTC or UT, is: " + prefix);

        }

        if (offset.getTotalSeconds() != 0) {

            prefix = prefix.concat(offset.getId());

        }

        return new ZoneRegion(prefix, offset.getRules());

    }

    /**

     * Parses the ID, taking a flag to indicate whether {@code ZoneRulesException}

     * should be thrown or not, used in deserialization.

     *

     * @param zoneId  the time-zone ID, not null

     * @param checkAvailable  whether to check if the zone ID is available

     * @return the zone ID, not null

     * @throws DateTimeException if the ID format is invalid

     * @throws ZoneRulesException if checking availability and the ID cannot be found

     */

    static ZoneId of(String zoneId, boolean checkAvailable) {

        Objects.requireNonNull(zoneId, "zoneId");

        if (zoneId.length() <= 1 || zoneId.startsWith("+") || zoneId.startsWith("-")) {

            return ZoneOffset.of(zoneId);

        } else if (zoneId.startsWith("UTC") || zoneId.startsWith("GMT")) {

            return ofWithPrefix(zoneId, 3, checkAvailable);

        } else if (zoneId.startsWith("UT")) {

            return ofWithPrefix(zoneId, 2, checkAvailable);

        }

        return ZoneRegion.ofId(zoneId, checkAvailable);

    }

    /**

     * Parse once a prefix is established.

     *

     * @param zoneId  the time-zone ID, not null

     * @param prefixLength  the length of the prefix, 2 or 3

     * @return the zone ID, not null

     * @throws DateTimeException if the zone ID has an invalid format

     */

    private static ZoneId ofWithPrefix(String zoneId, int prefixLength, boolean checkAvailable) {

        String prefix = zoneId.substring(0, prefixLength);

        if (zoneId.length() == prefixLength) {

            return ofOffset(prefix, ZoneOffset.UTC);

        }

        if (zoneId.charAt(prefixLength) != '+' && zoneId.charAt(prefixLength) != '-') {

            return ZoneRegion.ofId(zoneId, checkAvailable);  // drop through to ZoneRulesProvider

        }

        try {

            ZoneOffset offset = ZoneOffset.of(zoneId.substring(prefixLength));

            if (offset == ZoneOffset.UTC) {

                return ofOffset(prefix, offset);

            }

            return ofOffset(prefix, offset);

        } catch (DateTimeException ex) {

            throw new DateTimeException("Invalid ID for offset-based ZoneId: " + zoneId, ex);

        }

    }

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

    /**

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

     * <p>

     * This obtains a zone 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 ZoneId}.

     * <p>

     * A {@code TemporalAccessor} represents some form of date and time information.

     * This factory converts the arbitrary temporal object to an instance of {@code ZoneId}.

     * <p>

     * The conversion will try to obtain the zone in a way that favours region-based

     * zones over offset-based zones using {@link TemporalQuery#zone()}.

     * <p>

     * This method matches the signature of the functional interface {@link TemporalQuery}

     * allowing it to be used in queries via method reference, {@code ZoneId::from}.

     *

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

     * @return the zone ID, not null

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

     */

    public static ZoneId from(TemporalAccessor temporal) {

        ZoneId obj = temporal.query(TemporalQuery.zone());

        if (obj == null) {

            throw new DateTimeException("Unable to obtain ZoneId from TemporalAccessor: " + temporal.getClass());

        }

        return obj;

    }