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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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
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 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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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.InvalidObjectException;
import java.io.ObjectInputStream;
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.TemporalQueries;
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.HashSet;
import java.util.Locale;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import java.util.TimeZone;

import static java.util.Map.entry;


A time-zone ID, such as Europe/Paris. 
 A ZoneId is used to identify the rules used to convert between an Instant and a LocalDateTime. There are two distinct types of ID: 
    

  • Fixed offsets - a fully resolved offset from UTC/Greenwich, that uses
 the same offset for all local date-times

  • Geographical regions - an area where a specific set of rules for finding
 the offset from UTC/Greenwich apply

 Most fixed offsets are represented by ZoneOffset. Calling normalized() on any ZoneId will ensure that a fixed offset ID will be represented as a ZoneOffset. 
 The actual rules, describing when and how the offset changes, are defined by 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. 
 The distinction has other effects. Serializing the 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. 
Time-zone IDs

The ID is unique within the system.
There are three types of ID.

 The simplest type of ID is that from ZoneOffset. This consists of 'Z' and IDs starting with '+' or '-'. 
 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 ZoneOffset using normalized(). 
 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 ZoneRulesProvider. The configuration focuses on providing the lookup from the ID to the underlying ZoneRules. 

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.


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.


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'.

Serialization
 This class can be serialized and stores the string zone ID in the external form. The ZoneOffset subclass uses a dedicated format that only stores the offset from UTC/Greenwich. 
 A 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 ZoneId object will exist, and can be queried using getId, equals, hashCode, toString, getDisplayName and normalized. However, any call to getRules will fail with ZoneRulesException. This approach is designed to allow a ZonedDateTime to be loaded and queried, but not modified, on a Java Runtime with incomplete time-zone information. 

This is a value-based class; use of identity-sensitive operations (including reference equality (==), identity hash code, or synchronization) on instances of ZoneId may have unpredictable results and should be avoided. The equals method should be used for comparisons. 
Implementation Requirements: This abstract class has two implementations, both of which are immutable and thread-safe. One implementation models region-based IDs, the other is ZoneOffset modelling offset-based IDs. This difference is visible in serialization.
Since:1.8
/**
 * 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:
 * <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>
 * 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.
 *
 * <p>
 * This is a <a href="{@docRoot}/java.base/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 ZoneId} may have unpredictable results and should be avoided.
 * The {@code equals} method should be used for comparisons.
 *
 * @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 short time-zone names to be used.

 Use of short zone IDs has been deprecated in java.util.TimeZone. This map allows the IDs to continue to be used via the of(String, Map<String,String>) factory method. 

This map contains a mapping of the IDs that is in line with TZDB 2005r and
later, where 'EST', 'MST' and 'HST' map to IDs which do not include daylight
savings.


This maps as follows:

    

  • EST - -05:00
    • 

  • HST - -10:00
    • 

  • MST - -07:00
    • 

  • ACT - Australia/Darwin
    • 

  • AET - Australia/Sydney
    • 

  • AGT - America/Argentina/Buenos_Aires
    • 

  • ART - Africa/Cairo
    • 

  • AST - America/Anchorage
    • 

  • BET - America/Sao_Paulo
    • 

  • BST - Asia/Dhaka
    • 

  • CAT - Africa/Harare
    • 

  • CNT - America/St_Johns
    • 

  • CST - America/Chicago
    • 

  • CTT - Asia/Shanghai
    • 

  • EAT - Africa/Addis_Ababa
    • 

  • ECT - Europe/Paris
    • 

  • IET - America/Indiana/Indianapolis
    • 

  • IST - Asia/Kolkata
    • 

  • JST - Asia/Tokyo
    • 

  • MIT - Pacific/Apia
    • 

  • NET - Asia/Yerevan
    • 

  • NST - Pacific/Auckland
    • 

  • PLT - Asia/Karachi
    • 

  • PNT - America/Phoenix
    • 

  • PRT - America/Puerto_Rico
    • 

  • PST - America/Los_Angeles
    • 

  • SST - Pacific/Guadalcanal
    • 

  • VST - Asia/Ho_Chi_Minh
    • 


The map is unmodifiable.

/**
     * 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 mapping of the IDs that is in line with TZDB 2005r and
     * later, where 'EST', 'MST' and 'HST' map to IDs which do not include daylight
     * savings.
     * <p>
     * This maps as follows:
     * <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>
     * The map is unmodifiable.
     */
    public static final Map<String, String> SHORT_IDS = Map.ofEntries(
        entry("ACT", "Australia/Darwin"),
        entry("AET", "Australia/Sydney"),
        entry("AGT", "America/Argentina/Buenos_Aires"),
        entry("ART", "Africa/Cairo"),
        entry("AST", "America/Anchorage"),
        entry("BET", "America/Sao_Paulo"),
        entry("BST", "Asia/Dhaka"),
        entry("CAT", "Africa/Harare"),
        entry("CNT", "America/St_Johns"),
        entry("CST", "America/Chicago"),
        entry("CTT", "Asia/Shanghai"),
        entry("EAT", "Africa/Addis_Ababa"),
        entry("ECT", "Europe/Paris"),
        entry("IET", "America/Indiana/Indianapolis"),
        entry("IST", "Asia/Kolkata"),
        entry("JST", "Asia/Tokyo"),
        entry("MIT", "Pacific/Apia"),
        entry("NET", "Asia/Yerevan"),
        entry("NST", "Pacific/Auckland"),
        entry("PLT", "Asia/Karachi"),
        entry("PNT", "America/Phoenix"),
        entry("PRT", "America/Puerto_Rico"),
        entry("PST", "America/Los_Angeles"),
        entry("SST", "Pacific/Guadalcanal"),
        entry("VST", "Asia/Ho_Chi_Minh"),
        entry("EST", "-05:00"),
        entry("MST", "-07:00"),
        entry("HST", "-10:00")
    );
    
Serialization version.

/**
     * Serialization version.
     */
    private static final long serialVersionUID = 8352817235686L;

    //-----------------------------------------------------------------------
    
Gets the system default time-zone.

 This queries TimeZone.getDefault() to find the default time-zone and converts it to a ZoneId. If the system default time-zone is changed, then the result of this method will also change. 
Throws:
Returns:the zone ID, not null
/**
     * 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 TimeZone.getDefault().toZoneId();
    }

    
Gets the set of available zone IDs.

 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 of(String) to create a ZoneId. 

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.

Returns:a modifiable copy of the set of zone IDs, not null
/**
     * 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 new HashSet<String>(ZoneRulesProvider.getAvailableZoneIds());
    }

    //-----------------------------------------------------------------------
    
Obtains an instance of ZoneId using its ID using a map of aliases to supplement the standard zone IDs. 

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.

Params:
  • zoneId –  the time-zone ID, not null
  • aliasMap –  a map of alias zone IDs (typically abbreviations) to real zone IDs, not null
Throws:
Returns:the zone ID, not null
/**
     * 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 = Objects.requireNonNullElse(aliasMap.get(zoneId), zoneId);
        return of(id);
    }

    
Obtains an instance of ZoneId from an ID ensuring that the ID is valid and available for use. 
 This method parses the ID producing a ZoneId or ZoneOffset. A ZoneOffset is returned if the ID is 'Z', or starts with '+' or '-'. The result will always be a valid ID for which ZoneRules can be obtained. 

Parsing matches the zone ID step by step as follows.

    

  • If the zone ID equals 'Z', the result is ZoneOffset.UTC. 
  • If the zone ID consists of a single letter, the zone ID is invalid and DateTimeException is thrown. 
  • If the zone ID starts with '+' or '-', the ID is parsed as a ZoneOffset using ZoneOffset.of(String). 
  • If the zone ID equals 'GMT', 'UTC' or 'UT' then the result is a ZoneId with the same ID and rules equivalent to ZoneOffset.UTC. 
  • 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 ZoneOffset. The result will be a ZoneId with the specified UTC/GMT/UT prefix and the normalized offset ID as per ZoneOffset.getId(). The rules of the returned ZoneId will be equivalent to the parsed ZoneOffset. 
  • All other IDs are parsed as region-based zone IDs. Region IDs must
 match the regular expression [A-Za-z][A-Za-z0-9~/._+-]+ otherwise a DateTimeException is thrown. If the zone ID is not in the configured set of IDs, 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 TimeZone. 


Params:
  • zoneId –  the time-zone ID, not null
Throws:
Returns:the zone ID, not null
/**
     * 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 ZoneId wrapping an offset. 
 If the prefix is "GMT", "UTC", or "UT" a ZoneId with the prefix and the non-zero offset is returned. If the prefix is empty "" the ZoneOffset is returned. 
Params:
  • prefix –  the time-zone ID, not null
  • offset –  the offset, not null
Throws:
Returns:the zone ID, not null
/**
     * 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.isEmpty()) {
            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 ZoneRulesException should be thrown or not, used in deserialization. 
Params:
  • zoneId –  the time-zone ID, not null
  • checkAvailable –  whether to check if the zone ID is available
Throws:
Returns:the zone ID, not null
/**
     * 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.

Params:
  • zoneId –  the time-zone ID, not null
  • prefixLength –  the length of the prefix, 2 or 3
Throws:
Returns:the zone ID, not null
/**
     * 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 ZoneId from a temporal object. 
 This obtains a zone based on the specified temporal. A TemporalAccessor represents an arbitrary set of date and time information, which this factory converts to an instance of ZoneId. 
 A TemporalAccessor represents some form of date and time information. This factory converts the arbitrary temporal object to an instance of ZoneId. 
 The conversion will try to obtain the zone in a way that favours region-based zones over offset-based zones using TemporalQueries.zone(). 
 This method matches the signature of the functional interface TemporalQuery allowing it to be used as a query via method reference, ZoneId::from. 
Params:
  • temporal –  the temporal object to convert, not null
Throws:
Returns:the zone ID, not null
/**
     * 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 TemporalQueries#zone()}.
     * <p>
     * This method matches the signature of the functional interface {@link TemporalQuery}
     * allowing it to be used as a query 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(TemporalQueries.zone());
        if (obj == null) {
            throw new DateTimeException("Unable to obtain ZoneId from TemporalAccessor: " +
                    temporal + " of type " + temporal.getClass().getName());
        }
        return obj;
    }

    //-----------------------------------------------------------------------
    
Constructor only accessible within the package.

/**
     * Constructor only accessible within the package.
     */
    ZoneId() {
        if (getClass() != ZoneOffset.class && getClass() != ZoneRegion.class) {
            throw new AssertionError("Invalid subclass");
        }
    }

    //-----------------------------------------------------------------------
    
Gets the unique time-zone ID.

 This ID uniquely defines this object. The format of an offset based ID is defined by ZoneOffset.getId(). 
Returns:the time-zone unique ID, not null
/**
     * Gets the unique time-zone ID.
     * <p>
     * This ID uniquely defines this object.
     * The format of an offset based ID is defined by {@link ZoneOffset#getId()}.
     *
     * @return the time-zone unique ID, not null
     */
    public abstract String getId();

    //-----------------------------------------------------------------------
    
Gets the textual representation of the zone, such as 'British Time' or
'+02:00'.


This returns the textual name used to identify the time-zone ID,
suitable for presentation to the user.
The parameters control the style of the returned text and the locale.

 If no textual mapping is found then the full ID is returned. 
Params:
  • style –  the length of the text required, not null
  • locale –  the locale to use, not null
Returns:the text value of the zone, not null
/**
     * Gets the textual representation of the zone, such as 'British Time' or
     * '+02:00'.
     * <p>
     * This returns the textual name used to identify the time-zone ID,
     * suitable for presentation to the user.
     * The parameters control the style of the returned text and the locale.
     * <p>
     * If no textual mapping is found then the {@link #getId() full ID} is returned.
     *
     * @param style  the length of the text required, not null
     * @param locale  the locale to use, not null
     * @return the text value of the zone, not null
     */
    public String getDisplayName(TextStyle style, Locale locale) {
        return new DateTimeFormatterBuilder().appendZoneText(style).toFormatter(locale).format(toTemporal());
    }

    
Converts this zone to a TemporalAccessor. 
 A ZoneId can be fully represented as a TemporalAccessor. However, the interface is not implemented by this class as most of the methods on the interface have no meaning to ZoneId. 
 The returned temporal has no supported fields, with the query method supporting the return of the zone using TemporalQueries.zoneId(). 
Returns:a temporal equivalent to this zone, not null
/**
     * Converts this zone to a {@code TemporalAccessor}.
     * <p>
     * A {@code ZoneId} can be fully represented as a {@code TemporalAccessor}.
     * However, the interface is not implemented by this class as most of the
     * methods on the interface have no meaning to {@code ZoneId}.
     * <p>
     * The returned temporal has no supported fields, with the query method
     * supporting the return of the zone using {@link TemporalQueries#zoneId()}.
     *
     * @return a temporal equivalent to this zone, not null
     */
    private TemporalAccessor toTemporal() {
        return new TemporalAccessor() {
            @Override
            public boolean isSupported(TemporalField field) {
                return false;
            }
            @Override
            public long getLong(TemporalField field) {
                throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
            }
            @SuppressWarnings("unchecked")
            @Override
            public <R> R query(TemporalQuery<R> query) {
                if (query == TemporalQueries.zoneId()) {
                    return (R) ZoneId.this;
                }
                return TemporalAccessor.super.query(query);
            }
        };
    }

    //-----------------------------------------------------------------------
    
Gets the time-zone rules for this ID allowing calculations to be performed.


The rules provide the functionality associated with a time-zone,
such as finding the offset for a given instant or local date-time.

 A time-zone can be invalid if it is deserialized in a Java Runtime which does not have the same rules loaded as the Java Runtime that stored it. In this case, calling this method will throw a ZoneRulesException. 
 The rules are supplied by ZoneRulesProvider. An advanced provider may support dynamic updates to the rules without restarting the Java Runtime. If so, then the result of this method may change over time. Each individual call will be still remain thread-safe. 
 ZoneOffset will always return a set of rules where the offset never changes. 
Throws:
Returns:the rules, not null
/**
     * Gets the time-zone rules for this ID allowing calculations to be performed.
     * <p>
     * The rules provide the functionality associated with a time-zone,
     * such as finding the offset for a given instant or local date-time.
     * <p>
     * A time-zone can be invalid if it is deserialized in a Java Runtime which
     * does not have the same rules loaded as the Java Runtime that stored it.
     * In this case, calling this method will throw a {@code ZoneRulesException}.
     * <p>
     * The rules are supplied by {@link ZoneRulesProvider}. An advanced provider may
     * support dynamic updates to the rules without restarting the Java Runtime.
     * If so, then the result of this method may change over time.
     * Each individual call will be still remain thread-safe.
     * <p>
     * {@link ZoneOffset} will always return a set of rules where the offset never changes.
     *
     * @return the rules, not null
     * @throws ZoneRulesException if no rules are available for this ID
     */
    public abstract ZoneRules getRules();

    
Normalizes the time-zone ID, returning a ZoneOffset where possible. 
 The returns a normalized ZoneId that can be used in place of this ID. The result will have ZoneRules equivalent to those returned by this object, however the ID returned by getId() may be different. 
 The normalization checks if the rules of this ZoneId have a fixed offset. If they do, then the ZoneOffset equal to that offset is returned. Otherwise this is returned. 
Returns:the time-zone unique ID, not null
/**
     * Normalizes the time-zone ID, returning a {@code ZoneOffset} where possible.
     * <p>
     * The returns a normalized {@code ZoneId} that can be used in place of this ID.
     * The result will have {@code ZoneRules} equivalent to those returned by this object,
     * however the ID returned by {@code getId()} may be different.
     * <p>
     * The normalization checks if the rules of this {@code ZoneId} have a fixed offset.
     * If they do, then the {@code ZoneOffset} equal to that offset is returned.
     * Otherwise {@code this} is returned.
     *
     * @return the time-zone unique ID, not null
     */
    public ZoneId normalized() {
        try {
            ZoneRules rules = getRules();
            if (rules.isFixedOffset()) {
                return rules.getOffset(Instant.EPOCH);
            }
        } catch (ZoneRulesException ex) {
            // invalid ZoneRegion is not important to this method
        }
        return this;
    }

    //-----------------------------------------------------------------------
    
Checks if this time-zone ID is equal to another time-zone ID.


The comparison is based on the ID.

Params:
  • obj –  the object to check, null returns false
Returns:true if this is equal to the other time-zone ID
/**
     * Checks if this time-zone ID is equal to another time-zone ID.
     * <p>
     * The comparison is based on the ID.
     *
     * @param obj  the object to check, null returns false
     * @return true if this is equal to the other time-zone ID
     */
    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
           return true;
        }
        if (obj instanceof ZoneId) {
            ZoneId other = (ZoneId) obj;
            return getId().equals(other.getId());
        }
        return false;
    }

    
A hash code for this time-zone ID.

Returns:a suitable hash code
/**
     * A hash code for this time-zone ID.
     *
     * @return a suitable hash code
     */
    @Override
    public int hashCode() {
        return getId().hashCode();
    }

    //-----------------------------------------------------------------------
    
Defend against malicious streams.

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

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

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

@serialData

 out.writeByte(7);  // identifies a ZoneId (not ZoneOffset)
 out.writeUTF(getId());



 When read back in, the ZoneId will be created as though using of(String), but without any exception in the case where the ID has a valid format, but is not in the known set of region-based IDs.
Returns:the instance of Ser, not null
/**
     * Writes the object using a
     * <a href="../../serialized-form.html#java.time.Ser">dedicated serialized form</a>.
     * @serialData
     * <pre>
     *  out.writeByte(7);  // identifies a ZoneId (not ZoneOffset)
     *  out.writeUTF(getId());
     * </pre>
     * <p>
     * When read back in, the {@code ZoneId} will be created as though using
     * {@link #of(String)}, but without any exception in the case where the
     * ID has a valid format, but is not in the known set of region-based IDs.
     *
     * @return the instance of {@code Ser}, not null
     */
    // this is here for serialization Javadoc
    private Object writeReplace() {
        return new Ser(Ser.ZONE_REGION_TYPE, this);
    }

    abstract void write(DataOutput out) throws IOException;

}