/*

 * Copyright (c) 1996, 2018, 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

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/*

 * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved

 * (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved

 *

 * The original version of this source code and documentation

 * is copyrighted and owned by Taligent, Inc., a wholly-owned

 * subsidiary of IBM. These materials are provided under terms

 * of a License Agreement between Taligent and Sun. This technology

 * is protected by multiple US and International patents.

 *

 * This notice and attribution to Taligent may not be removed.

 * Taligent is a registered trademark of Taligent, Inc.

 *

 */

package java.util;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.io.ObjectStreamField;

import java.io.Serializable;

import java.text.MessageFormat;

import java.util.concurrent.ConcurrentHashMap;

import java.util.spi.LocaleNameProvider;

import java.util.stream.Collectors;

import sun.security.action.GetPropertyAction;

import sun.util.locale.BaseLocale;

import sun.util.locale.InternalLocaleBuilder;

import sun.util.locale.LanguageTag;

import sun.util.locale.LocaleExtensions;

import sun.util.locale.LocaleMatcher;

import sun.util.locale.LocaleObjectCache;

import sun.util.locale.LocaleSyntaxException;

import sun.util.locale.LocaleUtils;

import sun.util.locale.ParseStatus;

import sun.util.locale.provider.LocaleProviderAdapter;

import sun.util.locale.provider.LocaleResources;

import sun.util.locale.provider.LocaleServiceProviderPool;

import sun.util.locale.provider.TimeZoneNameUtility;

/**

 * A <code>Locale</code> object represents a specific geographical, political,

 * or cultural region. An operation that requires a <code>Locale</code> to perform

 * its task is called <em>locale-sensitive</em> and uses the <code>Locale</code>

 * to tailor information for the user. For example, displaying a number

 * is a locale-sensitive operation— the number should be formatted

 * according to the customs and conventions of the user's native country,

 * region, or culture.

 *

 * <p> The {@code Locale} class implements IETF BCP 47 which is composed of

 * <a href="http://tools.ietf.org/html/rfc4647">RFC 4647 "Matching of Language

 * Tags"</a> and <a href="http://tools.ietf.org/html/rfc5646">RFC 5646 "Tags

 * for Identifying Languages"</a> with support for the LDML (UTS#35, "Unicode

 * Locale Data Markup Language") BCP 47-compatible extensions for locale data

 * exchange.

 *

 * <p> A <code>Locale</code> object logically consists of the fields

 * described below.

 *

 * <dl>

 *   <dt><a id="def_language"><b>language</b></a></dt>

 *

 *   <dd>ISO 639 alpha-2 or alpha-3 language code, or registered

 *   language subtags up to 8 alpha letters (for future enhancements).

 *   When a language has both an alpha-2 code and an alpha-3 code, the

 *   alpha-2 code must be used.  You can find a full list of valid

 *   language codes in the IANA Language Subtag Registry (search for

 *   "Type: language").  The language field is case insensitive, but

 *   <code>Locale</code> always canonicalizes to lower case.</dd>

 *

 *   <dd>Well-formed language values have the form

 *   <code>[a-zA-Z]{2,8}</code>.  Note that this is not the full

 *   BCP47 language production, since it excludes extlang.  They are

 *   not needed since modern three-letter language codes replace

 *   them.</dd>

 *

 *   <dd>Example: "en" (English), "ja" (Japanese), "kok" (Konkani)</dd>

 *

 *   <dt><a id="def_script"><b>script</b></a></dt>

 *

 *   <dd>ISO 15924 alpha-4 script code.  You can find a full list of

 *   valid script codes in the IANA Language Subtag Registry (search

 *   for "Type: script").  The script field is case insensitive, but

 *   <code>Locale</code> always canonicalizes to title case (the first

 *   letter is upper case and the rest of the letters are lower

 *   case).</dd>

 *

 *   <dd>Well-formed script values have the form

 *   <code>[a-zA-Z]{4}</code></dd>

 *

 *   <dd>Example: "Latn" (Latin), "Cyrl" (Cyrillic)</dd>

 *

 *   <dt><a id="def_region"><b>country (region)</b></a></dt>

 *

 *   <dd>ISO 3166 alpha-2 country code or UN M.49 numeric-3 area code.

 *   You can find a full list of valid country and region codes in the

 *   IANA Language Subtag Registry (search for "Type: region").  The

 *   country (region) field is case insensitive, but

 *   <code>Locale</code> always canonicalizes to upper case.</dd>

 *

 *   <dd>Well-formed country/region values have

 *   the form <code>[a-zA-Z]{2} | [0-9]{3}</code></dd>

 *

 *   <dd>Example: "US" (United States), "FR" (France), "029"

 *   (Caribbean)</dd>

 *

 *   <dt><a id="def_variant"><b>variant</b></a></dt>

 *

 *   <dd>Any arbitrary value used to indicate a variation of a

 *   <code>Locale</code>.  Where there are two or more variant values

 *   each indicating its own semantics, these values should be ordered

 *   by importance, with most important first, separated by

 *   underscore('_').  The variant field is case sensitive.</dd>

 *

 *   <dd>Note: IETF BCP 47 places syntactic restrictions on variant

 *   subtags.  Also BCP 47 subtags are strictly used to indicate

 *   additional variations that define a language or its dialects that

 *   are not covered by any combinations of language, script and

 *   region subtags.  You can find a full list of valid variant codes

 *   in the IANA Language Subtag Registry (search for "Type: variant").

 *

 *   <p>However, the variant field in <code>Locale</code> has

 *   historically been used for any kind of variation, not just

 *   language variations.  For example, some supported variants

 *   available in Java SE Runtime Environments indicate alternative

 *   cultural behaviors such as calendar type or number script.  In

 *   BCP 47 this kind of information, which does not identify the

 *   language, is supported by extension subtags or private use

 *   subtags.</dd>

 *

 *   <dd>Well-formed variant values have the form <code>SUBTAG

 *   (('_'|'-') SUBTAG)*</code> where <code>SUBTAG =

 *   [0-9][0-9a-zA-Z]{3} | [0-9a-zA-Z]{5,8}</code>. (Note: BCP 47 only

 *   uses hyphen ('-') as a delimiter, this is more lenient).</dd>

 *

 *   <dd>Example: "polyton" (Polytonic Greek), "POSIX"</dd>

 *

 *   <dt><a id="def_extensions"><b>extensions</b></a></dt>

 *

 *   <dd>A map from single character keys to string values, indicating

 *   extensions apart from language identification.  The extensions in

 *   <code>Locale</code> implement the semantics and syntax of BCP 47

 *   extension subtags and private use subtags. The extensions are

 *   case insensitive, but <code>Locale</code> canonicalizes all

 *   extension keys and values to lower case. Note that extensions

 *   cannot have empty values.</dd>

 *

 *   <dd>Well-formed keys are single characters from the set

 *   <code>[0-9a-zA-Z]</code>.  Well-formed values have the form

 *   <code>SUBTAG ('-' SUBTAG)*</code> where for the key 'x'

 *   <code>SUBTAG = [0-9a-zA-Z]{1,8}</code> and for other keys

 *   <code>SUBTAG = [0-9a-zA-Z]{2,8}</code> (that is, 'x' allows

 *   single-character subtags).</dd>

 *

 *   <dd>Example: key="u"/value="ca-japanese" (Japanese Calendar),

 *   key="x"/value="java-1-7"</dd>

 * </dl>

 *

 * <b>Note:</b> Although BCP 47 requires field values to be registered

 * in the IANA Language Subtag Registry, the <code>Locale</code> class

 * does not provide any validation features.  The <code>Builder</code>

 * only checks if an individual field satisfies the syntactic

 * requirement (is well-formed), but does not validate the value

 * itself.  See {@link Builder} for details.

 *

 * <h3><a id="def_locale_extension">Unicode locale/language extension</a></h3>

 *

 * <p>UTS#35, "Unicode Locale Data Markup Language" defines optional

 * attributes and keywords to override or refine the default behavior

 * associated with a locale.  A keyword is represented by a pair of

 * key and type.  For example, "nu-thai" indicates that Thai local

 * digits (value:"thai") should be used for formatting numbers

 * (key:"nu").

 *

 * <p>The keywords are mapped to a BCP 47 extension value using the

 * extension key 'u' ({@link #UNICODE_LOCALE_EXTENSION}).  The above

 * example, "nu-thai", becomes the extension "u-nu-thai".

 *

 * <p>Thus, when a <code>Locale</code> object contains Unicode locale

 * attributes and keywords,

 * <code>getExtension(UNICODE_LOCALE_EXTENSION)</code> will return a

 * String representing this information, for example, "nu-thai".  The

 * <code>Locale</code> class also provides {@link

 * #getUnicodeLocaleAttributes}, {@link #getUnicodeLocaleKeys}, and

 * {@link #getUnicodeLocaleType} which allow you to access Unicode

 * locale attributes and key/type pairs directly.  When represented as

 * a string, the Unicode Locale Extension lists attributes

 * alphabetically, followed by key/type sequences with keys listed

 * alphabetically (the order of subtags comprising a key's type is

 * fixed when the type is defined)

 *

 * <p>A well-formed locale key has the form

 * <code>[0-9a-zA-Z]{2}</code>.  A well-formed locale type has the

 * form <code>"" | [0-9a-zA-Z]{3,8} ('-' [0-9a-zA-Z]{3,8})*</code> (it

 * can be empty, or a series of subtags 3-8 alphanums in length).  A

 * well-formed locale attribute has the form

 * <code>[0-9a-zA-Z]{3,8}</code> (it is a single subtag with the same

 * form as a locale type subtag).

 *

 * <p>The Unicode locale extension specifies optional behavior in

 * locale-sensitive services.  Although the LDML specification defines

 * various keys and values, actual locale-sensitive service

 * implementations in a Java Runtime Environment might not support any

 * particular Unicode locale attributes or key/type pairs.

 *

 * <h4>Creating a Locale</h4>

 *

 * <p>There are several different ways to create a <code>Locale</code>

 * object.

 *

 * <h5>Builder</h5>

 *

 * <p>Using {@link Builder} you can construct a <code>Locale</code> object

 * that conforms to BCP 47 syntax.

 *

 * <h5>Constructors</h5>

 *

 * <p>The <code>Locale</code> class provides three constructors:

 * <blockquote>

 * <pre>

 *     {@link #Locale(String language)}

 *     {@link #Locale(String language, String country)}

 *     {@link #Locale(String language, String country, String variant)}

 * </pre>

 * </blockquote>

 * These constructors allow you to create a <code>Locale</code> object

 * with language, country and variant, but you cannot specify

 * script or extensions.

 *

 * <h5>Factory Methods</h5>

 *

 * <p>The method {@link #forLanguageTag} creates a <code>Locale</code>

 * object for a well-formed BCP 47 language tag.

 *

 * <h5>Locale Constants</h5>

 *

 * <p>The <code>Locale</code> class provides a number of convenient constants

 * that you can use to create <code>Locale</code> objects for commonly used

 * locales. For example, the following creates a <code>Locale</code> object

 * for the United States:

 * <blockquote>

 * <pre>

 *     Locale.US

 * </pre>

 * </blockquote>

 *

 * <h4><a id="LocaleMatching">Locale Matching</a></h4>

 *

 * <p>If an application or a system is internationalized and provides localized

 * resources for multiple locales, it sometimes needs to find one or more

 * locales (or language tags) which meet each user's specific preferences. Note

 * that a term "language tag" is used interchangeably with "locale" in this

 * locale matching documentation.

 *

 * <p>In order to do matching a user's preferred locales to a set of language

 * tags, <a href="http://tools.ietf.org/html/rfc4647">RFC 4647 Matching of

 * Language Tags</a> defines two mechanisms: filtering and lookup.

 * <em>Filtering</em> is used to get all matching locales, whereas

 * <em>lookup</em> is to choose the best matching locale.

 * Matching is done case-insensitively. These matching mechanisms are described

 * in the following sections.

 *

 * <p>A user's preference is called a <em>Language Priority List</em> and is

 * expressed as a list of language ranges. There are syntactically two types of

 * language ranges: basic and extended. See

 * {@link Locale.LanguageRange Locale.LanguageRange} for details.

 *

 * <h5>Filtering</h5>

 *

 * <p>The filtering operation returns all matching language tags. It is defined

 * in RFC 4647 as follows:

 * "In filtering, each language range represents the least specific language

 * tag (that is, the language tag with fewest number of subtags) that is an

 * acceptable match. All of the language tags in the matching set of tags will

 * have an equal or greater number of subtags than the language range. Every

 * non-wildcard subtag in the language range will appear in every one of the

 * matching language tags."

 *

 * <p>There are two types of filtering: filtering for basic language ranges

 * (called "basic filtering") and filtering for extended language ranges

 * (called "extended filtering"). They may return different results by what

 * kind of language ranges are included in the given Language Priority List.

 * {@link Locale.FilteringMode} is a parameter to specify how filtering should

 * be done.

 *

 * <h5>Lookup</h5>

 *

 * <p>The lookup operation returns the best matching language tags. It is

 * defined in RFC 4647 as follows:

 * "By contrast with filtering, each language range represents the most

 * specific tag that is an acceptable match.  The first matching tag found,

 * according to the user's priority, is considered the closest match and is the

 * item returned."

 *

 * <p>For example, if a Language Priority List consists of two language ranges,

 * {@code "zh-Hant-TW"} and {@code "en-US"}, in prioritized order, lookup

 * method progressively searches the language tags below in order to find the

 * best matching language tag.

 * <blockquote>

 * <pre>

 *    1. zh-Hant-TW

 *    2. zh-Hant

 *    3. zh

 *    4. en-US

 *    5. en

 * </pre>

 * </blockquote>

 * If there is a language tag which matches completely to a language range

 * above, the language tag is returned.

 *

 * <p>{@code "*"} is the special language range, and it is ignored in lookup.

 *

 * <p>If multiple language tags match as a result of the subtag {@code '*'}

 * included in a language range, the first matching language tag returned by

 * an {@link Iterator} over a {@link Collection} of language tags is treated as

 * the best matching one.

 *

 * <h4>Use of Locale</h4>

 *

 * <p>Once you've created a <code>Locale</code> you can query it for information

 * about itself. Use <code>getCountry</code> to get the country (or region)

 * code and <code>getLanguage</code> to get the language code.

 * You can use <code>getDisplayCountry</code> to get the

 * name of the country suitable for displaying to the user. Similarly,

 * you can use <code>getDisplayLanguage</code> to get the name of

 * the language suitable for displaying to the user. Interestingly,

 * the <code>getDisplayXXX</code> methods are themselves locale-sensitive

 * and have two versions: one that uses the default

 * {@link Locale.Category#DISPLAY DISPLAY} locale and one

 * that uses the locale specified as an argument.

 *

 * <p>The Java Platform provides a number of classes that perform locale-sensitive

 * operations. For example, the <code>NumberFormat</code> class formats

 * numbers, currency, and percentages in a locale-sensitive manner. Classes

 * such as <code>NumberFormat</code> have several convenience methods

 * for creating a default object of that type. For example, the

 * <code>NumberFormat</code> class provides these three convenience methods

 * for creating a default <code>NumberFormat</code> object:

 * <blockquote>

 * <pre>

 *     NumberFormat.getInstance()

 *     NumberFormat.getCurrencyInstance()

 *     NumberFormat.getPercentInstance()

 * </pre>

 * </blockquote>

 * Each of these methods has two variants; one with an explicit locale

 * and one without; the latter uses the default

 * {@link Locale.Category#FORMAT FORMAT} locale:

 * <blockquote>

 * <pre>

 *     NumberFormat.getInstance(myLocale)

 *     NumberFormat.getCurrencyInstance(myLocale)

 *     NumberFormat.getPercentInstance(myLocale)

 * </pre>

 * </blockquote>

 * A <code>Locale</code> is the mechanism for identifying the kind of object

 * (<code>NumberFormat</code>) that you would like to get. The locale is

 * <STRONG>just</STRONG> a mechanism for identifying objects,

 * <STRONG>not</STRONG> a container for the objects themselves.

 *

 * <h4>Compatibility</h4>

 *

 * <p>In order to maintain compatibility with existing usage, Locale's

 * constructors retain their behavior prior to the Java Runtime

 * Environment version 1.7.  The same is largely true for the

 * <code>toString</code> method. Thus Locale objects can continue to

 * be used as they were. In particular, clients who parse the output

 * of toString into language, country, and variant fields can continue

 * to do so (although this is strongly discouraged), although the

 * variant field will have additional information in it if script or

 * extensions are present.

 *

 * <p>In addition, BCP 47 imposes syntax restrictions that are not

 * imposed by Locale's constructors. This means that conversions

 * between some Locales and BCP 47 language tags cannot be made without

 * losing information. Thus <code>toLanguageTag</code> cannot

 * represent the state of locales whose language, country, or variant

 * do not conform to BCP 47.

 *

 * <p>Because of these issues, it is recommended that clients migrate

 * away from constructing non-conforming locales and use the

 * <code>forLanguageTag</code> and <code>Locale.Builder</code> APIs instead.

 * Clients desiring a string representation of the complete locale can

 * then always rely on <code>toLanguageTag</code> for this purpose.

 *

 * <h5><a id="special_cases_constructor">Special cases</a></h5>

 *

 * <p>For compatibility reasons, two

 * non-conforming locales are treated as special cases.  These are

 * <b>{@code ja_JP_JP}</b> and <b>{@code th_TH_TH}</b>. These are ill-formed

 * in BCP 47 since the variants are too short. To ease migration to BCP 47,

 * these are treated specially during construction.  These two cases (and only

 * these) cause a constructor to generate an extension, all other values behave

 * exactly as they did prior to Java 7.

 *

 * <p>Java has used {@code ja_JP_JP} to represent Japanese as used in

 * Japan together with the Japanese Imperial calendar. This is now

 * representable using a Unicode locale extension, by specifying the

 * Unicode locale key {@code ca} (for "calendar") and type

 * {@code japanese}. When the Locale constructor is called with the

 * arguments "ja", "JP", "JP", the extension "u-ca-japanese" is

 * automatically added.

 *

 * <p>Java has used {@code th_TH_TH} to represent Thai as used in

 * Thailand together with Thai digits. This is also now representable using

 * a Unicode locale extension, by specifying the Unicode locale key

 * {@code nu} (for "number") and value {@code thai}. When the Locale

 * constructor is called with the arguments "th", "TH", "TH", the

 * extension "u-nu-thai" is automatically added.

 *

 * <h5>Serialization</h5>

 *

 * <p>During serialization, writeObject writes all fields to the output

 * stream, including extensions.

 *

 * <p>During deserialization, readResolve adds extensions as described

 * in <a href="#special_cases_constructor">Special Cases</a>, only

 * for the two cases th_TH_TH and ja_JP_JP.

 *

 * <h5>Legacy language codes</h5>

 *

 * <p>Locale's constructor has always converted three language codes to

 * their earlier, obsoleted forms: {@code he} maps to {@code iw},

 * {@code yi} maps to {@code ji}, and {@code id} maps to

 * {@code in}.  This continues to be the case, in order to not break

 * backwards compatibility.

 *

 * <p>The APIs added in 1.7 map between the old and new language codes,

 * maintaining the old codes internal to Locale (so that

 * <code>getLanguage</code> and <code>toString</code> reflect the old

 * code), but using the new codes in the BCP 47 language tag APIs (so

 * that <code>toLanguageTag</code> reflects the new one). This

 * preserves the equivalence between Locales no matter which code or

 * API is used to construct them. Java's default resource bundle

 * lookup mechanism also implements this mapping, so that resources

 * can be named using either convention, see {@link ResourceBundle.Control}.

 *

 * <h5>Three-letter language/country(region) codes</h5>

 *

 * <p>The Locale constructors have always specified that the language

 * and the country param be two characters in length, although in

 * practice they have accepted any length.  The specification has now

 * been relaxed to allow language codes of two to eight characters and

 * country (region) codes of two to three characters, and in

 * particular, three-letter language codes and three-digit region

 * codes as specified in the IANA Language Subtag Registry.  For

 * compatibility, the implementation still does not impose a length

 * constraint.

 *

 * @see Builder

 * @see ResourceBundle

 * @see java.text.Format

 * @see java.text.NumberFormat

 * @see java.text.Collator

 * @author Mark Davis

 * @since 1.1

 */

public final class Locale implements Cloneable, Serializable {

    private static final  Cache LOCALECACHE = new Cache();

    /** Useful constant for language.

     */

    public static final Locale ENGLISH = createConstant("en", "");

    /** Useful constant for language.

     */

    public static final Locale FRENCH = createConstant("fr", "");

    /** Useful constant for language.

     */

    public static final Locale GERMAN = createConstant("de", "");

    /** Useful constant for language.

     */

    public static final Locale ITALIAN = createConstant("it", "");

    /** Useful constant for language.

     */

    public static final Locale JAPANESE = createConstant("ja", "");

    /** Useful constant for language.

     */

    public static final Locale KOREAN = createConstant("ko", "");

    /** Useful constant for language.

     */

    public static final Locale CHINESE = createConstant("zh", "");

    /** Useful constant for language.

     */

    public static final Locale SIMPLIFIED_CHINESE = createConstant("zh", "CN");

    /** Useful constant for language.

     */

    public static final Locale TRADITIONAL_CHINESE = createConstant("zh", "TW");

    /** Useful constant for country.

     */

    public static final Locale FRANCE = createConstant("fr", "FR");

    /** Useful constant for country.

     */

    public static final Locale GERMANY = createConstant("de", "DE");

    /** Useful constant for country.

     */

    public static final Locale ITALY = createConstant("it", "IT");

    /** Useful constant for country.

     */

    public static final Locale JAPAN = createConstant("ja", "JP");

    /** Useful constant for country.

     */

    public static final Locale KOREA = createConstant("ko", "KR");

    /** Useful constant for country.

     */

    public static final Locale CHINA = SIMPLIFIED_CHINESE;

    /** Useful constant for country.

     */

    public static final Locale PRC = SIMPLIFIED_CHINESE;

    /** Useful constant for country.

     */

    public static final Locale TAIWAN = TRADITIONAL_CHINESE;

    /** Useful constant for country.

     */

    public static final Locale UK = createConstant("en", "GB");

    /** Useful constant for country.

     */

    public static final Locale US = createConstant("en", "US");

    /** Useful constant for country.

     */

    public static final Locale CANADA = createConstant("en", "CA");

    /** Useful constant for country.

     */

    public static final Locale CANADA_FRENCH = createConstant("fr", "CA");

    /**

     * Useful constant for the root locale.  The root locale is the locale whose

     * language, country, and variant are empty ("") strings.  This is regarded

     * as the base locale of all locales, and is used as the language/country

     * neutral locale for the locale sensitive operations.

     *

     * @since 1.6

     */

    public static final Locale ROOT = createConstant("", "");

    /**

     * The key for the private use extension ('x').

     *

     * @see #getExtension(char)

     * @see Builder#setExtension(char, String)

     * @since 1.7

     */

    public static final char PRIVATE_USE_EXTENSION = 'x';

    /**

     * The key for Unicode locale extension ('u').

     *

     * @see #getExtension(char)

     * @see Builder#setExtension(char, String)

     * @since 1.7

     */

    public static final char UNICODE_LOCALE_EXTENSION = 'u';

    /** serialization ID

     */

    static final long serialVersionUID = 9149081749638150636L;

    /**

     * Enum for specifying the type defined in ISO 3166. This enum is used to

     * retrieve the two-letter ISO3166-1 alpha-2, three-letter ISO3166-1

     * alpha-3, four-letter ISO3166-3 country codes.

     *

     * @see #getISOCountries(Locale.IsoCountryCode)

     * @since 9

     */

    public static enum IsoCountryCode {

        /**

         * PART1_ALPHA2 is used to represent the ISO3166-1 alpha-2 two letter

         * country codes.

         */

        PART1_ALPHA2 {

            @Override

            Set<String> createCountryCodeSet() {

                return Set.of(Locale.getISOCountries());

            }

        },

        /**

         *

         * PART1_ALPHA3 is used to represent the ISO3166-1 alpha-3 three letter

         * country codes.

         */

        PART1_ALPHA3 {

            @Override

            Set<String> createCountryCodeSet() {

                return LocaleISOData.computeISO3166_1Alpha3Countries();

            }

        },

        /**

         * PART3 is used to represent the ISO3166-3 four letter country codes.

         */

        PART3 {

            @Override

            Set<String> createCountryCodeSet() {

                return Set.of(LocaleISOData.ISO3166_3);

            }

        };

        /**

         * Concrete implementation of this method attempts to compute value

         * for iso3166CodesMap for each IsoCountryCode type key.

         */

        abstract Set<String> createCountryCodeSet();

        /**

         * Map to hold country codes for each ISO3166 part.

         */

        private static Map<IsoCountryCode, Set<String>> iso3166CodesMap = new ConcurrentHashMap<>();

        /**

         * This method is called from Locale class to retrieve country code set

         * for getISOCountries(type)

         */

        static Set<String> retrieveISOCountryCodes(IsoCountryCode type) {

            return iso3166CodesMap.computeIfAbsent(type, IsoCountryCode::createCountryCodeSet);

        }

    }

    /**

     * Display types for retrieving localized names from the name providers.

     */

    private static final int DISPLAY_LANGUAGE  = 0;

    private static final int DISPLAY_COUNTRY   = 1;

    private static final int DISPLAY_VARIANT   = 2;

    private static final int DISPLAY_SCRIPT    = 3;

    private static final int DISPLAY_UEXT_KEY  = 4;

    private static final int DISPLAY_UEXT_TYPE = 5;

    /**

     * Private constructor used by getInstance method

     */

    private Locale(BaseLocale baseLocale, LocaleExtensions extensions) {

        this.baseLocale = baseLocale;

        this.localeExtensions = extensions;

    }

    /**

     * Construct a locale from language, country and variant.

     * This constructor normalizes the language value to lowercase and

     * the country value to uppercase.

     * <p>

     * <b>Note:</b>

     * <ul>

     * <li>ISO 639 is not a stable standard; some of the language codes it defines

     * (specifically "iw", "ji", and "in") have changed.  This constructor accepts both the

     * old codes ("iw", "ji", and "in") and the new codes ("he", "yi", and "id"), but all other

     * API on Locale will return only the OLD codes.

     * <li>For backward compatibility reasons, this constructor does not make

     * any syntactic checks on the input.

     * <li>The two cases ("ja", "JP", "JP") and ("th", "TH", "TH") are handled specially,

     * see <a href="#special_cases_constructor">Special Cases</a> for more information.

     * </ul>

     *

     * @param language An ISO 639 alpha-2 or alpha-3 language code, or a language subtag

     * up to 8 characters in length.  See the <code>Locale</code> class description about

     * valid language values.

     * @param country An ISO 3166 alpha-2 country code or a UN M.49 numeric-3 area code.

     * See the <code>Locale</code> class description about valid country values.

     * @param variant Any arbitrary value used to indicate a variation of a <code>Locale</code>.

     * See the <code>Locale</code> class description for the details.

     * @exception NullPointerException thrown if any argument is null.

     */

    public Locale(String language, String country, String variant) {

        if (language== null || country == null || variant == null) {

            throw new NullPointerException();

        }

        baseLocale = BaseLocale.getInstance(convertOldISOCodes(language), "", country, variant);

        localeExtensions = getCompatibilityExtensions(language, "", country, variant);

    }

    /**

     * Construct a locale from language and country.

     * This constructor normalizes the language value to lowercase and

     * the country value to uppercase.

     * <p>

     * <b>Note:</b>

     * <ul>

     * <li>ISO 639 is not a stable standard; some of the language codes it defines

     * (specifically "iw", "ji", and "in") have changed.  This constructor accepts both the

     * old codes ("iw", "ji", and "in") and the new codes ("he", "yi", and "id"), but all other

     * API on Locale will return only the OLD codes.

     * <li>For backward compatibility reasons, this constructor does not make

     * any syntactic checks on the input.

     * </ul>

     *

     * @param language An ISO 639 alpha-2 or alpha-3 language code, or a language subtag

     * up to 8 characters in length.  See the <code>Locale</code> class description about

     * valid language values.

     * @param country An ISO 3166 alpha-2 country code or a UN M.49 numeric-3 area code.

     * See the <code>Locale</code> class description about valid country values.

     * @exception NullPointerException thrown if either argument is null.

     */

    public Locale(String language, String country) {

        this(language, country, "");

    }

    /**

     * Construct a locale from a language code.

     * This constructor normalizes the language value to lowercase.

     * <p>

     * <b>Note:</b>

     * <ul>

     * <li>ISO 639 is not a stable standard; some of the language codes it defines

     * (specifically "iw", "ji", and "in") have changed.  This constructor accepts both the

     * old codes ("iw", "ji", and "in") and the new codes ("he", "yi", and "id"), but all other

     * API on Locale will return only the OLD codes.

     * <li>For backward compatibility reasons, this constructor does not make

     * any syntactic checks on the input.

     * </ul>

     *

     * @param language An ISO 639 alpha-2 or alpha-3 language code, or a language subtag

     * up to 8 characters in length.  See the <code>Locale</code> class description about

     * valid language values.

     * @exception NullPointerException thrown if argument is null.

     * @since 1.4

     */

    public Locale(String language) {

        this(language, "", "");

    }

    /**

     * This method must be called only for creating the Locale.*

     * constants due to making shortcuts.

     */

    private static Locale createConstant(String lang, String country) {

        BaseLocale base = BaseLocale.createInstance(lang, country);

        return getInstance(base, null);

    }

    /**

     * Returns a <code>Locale</code> constructed from the given

     * <code>language</code>, <code>country</code> and

     * <code>variant</code>. If the same <code>Locale</code> instance

     * is available in the cache, then that instance is

     * returned. Otherwise, a new <code>Locale</code> instance is

     * created and cached.

     *

     * @param language lowercase 2 to 8 language code.

     * @param country uppercase two-letter ISO-3166 code and numeric-3 UN M.49 area code.

     * @param variant vendor and browser specific code. See class description.

     * @return the <code>Locale</code> instance requested

     * @exception NullPointerException if any argument is null.

     */

    static Locale getInstance(String language, String country, String variant) {

        return getInstance(language, "", country, variant, null);

    }

    static Locale getInstance(String language, String script, String country,

                                      String variant, LocaleExtensions extensions) {

        if (language== null || script == null || country == null || variant == null) {

            throw new NullPointerException();

        }

        if (extensions == null) {

            extensions = getCompatibilityExtensions(language, script, country, variant);

        }

        BaseLocale baseloc = BaseLocale.getInstance(language, script, country, variant);

        return getInstance(baseloc, extensions);

    }

    static Locale getInstance(BaseLocale baseloc, LocaleExtensions extensions) {

        if (extensions == null) {

            return LOCALECACHE.get(baseloc);

        } else {

            LocaleKey key = new LocaleKey(baseloc, extensions);

            return LOCALECACHE.get(key);

        }

    }

    private static class Cache extends LocaleObjectCache<Object, Locale> {

        private Cache() {

        }

        @Override

        protected Locale createObject(Object key) {

            if (key instanceof BaseLocale) {

                return new Locale((BaseLocale)key, null);

            } else {

                LocaleKey lk = (LocaleKey)key;

                return new Locale(lk.base, lk.exts);

            }

        }

    }

    private static final class LocaleKey {

        private final BaseLocale base;

        private final LocaleExtensions exts;

        private final int hash;

        private LocaleKey(BaseLocale baseLocale, LocaleExtensions extensions) {

            base = baseLocale;

            exts = extensions;

            // Calculate the hash value here because it's always used.

            int h = base.hashCode();

            if (exts != null) {

                h ^= exts.hashCode();

            }

            hash = h;

        }

        @Override

        public boolean equals(Object obj) {

            if (this == obj) {

                return true;

            }

            if (!(obj instanceof LocaleKey)) {

                return false;

            }

            LocaleKey other = (LocaleKey)obj;

            if (hash != other.hash || !base.equals(other.base)) {

                return false;

            }

            if (exts == null) {

                return other.exts == null;

            }

            return exts.equals(other.exts);

        }

        @Override

        public int hashCode() {

            return hash;

        }

    }

    /**

     * Gets the current value of the default locale for this instance

     * of the Java Virtual Machine.

     * <p>

     * The Java Virtual Machine sets the default locale during startup

     * based on the host environment. It is used by many locale-sensitive

     * methods if no locale is explicitly specified.

     * It can be changed using the

     * {@link #setDefault(java.util.Locale) setDefault} method.

     *

     * @return the default locale for this instance of the Java Virtual Machine

     */

    public static Locale getDefault() {

        // do not synchronize this method - see 4071298

        return defaultLocale;

    }

    /**

     * Gets the current value of the default locale for the specified Category

     * for this instance of the Java Virtual Machine.

     * <p>

     * The Java Virtual Machine sets the default locale during startup based

     * on the host environment. It is used by many locale-sensitive methods

     * if no locale is explicitly specified. It can be changed using the

     * setDefault(Locale.Category, Locale) method.

     *

     * @param category - the specified category to get the default locale

     * @throws NullPointerException if category is null

     * @return the default locale for the specified Category for this instance

     *     of the Java Virtual Machine

     * @see #setDefault(Locale.Category, Locale)

     * @since 1.7

     */

    public static Locale getDefault(Locale.Category category) {

        // do not synchronize this method - see 4071298

        switch (category) {

        case DISPLAY:

            if (defaultDisplayLocale == null) {

                synchronized(Locale.class) {

                    if (defaultDisplayLocale == null) {

                        defaultDisplayLocale = initDefault(category);

                    }

                }

            }

            return defaultDisplayLocale;

        case FORMAT:

            if (defaultFormatLocale == null) {

                synchronized(Locale.class) {

                    if (defaultFormatLocale == null) {

                        defaultFormatLocale = initDefault(category);

                    }

                }

            }

            return defaultFormatLocale;

        default:

            assert false: "Unknown Category";

        }

        return getDefault();

    }

    private static Locale initDefault() {

        String language, region, script, country, variant;

        Properties props = GetPropertyAction.privilegedGetProperties();

        language = props.getProperty("user.language", "en");

        // for compatibility, check for old user.region property

        region = props.getProperty("user.region");

        if (region != null) {

            // region can be of form country, country_variant, or _variant

            int i = region.indexOf('_');

            if (i >= 0) {

                country = region.substring(0, i);

                variant = region.substring(i + 1);

            } else {

                country = region;

                variant = "";

            }

            script = "";

        } else {

            script = props.getProperty("user.script", "");

            country = props.getProperty("user.country", "");

            variant = props.getProperty("user.variant", "");

        }

        return getInstance(language, script, country, variant,

                getDefaultExtensions(props.getProperty("user.extensions", ""))

                    .orElse(null));

    }

    private static Locale initDefault(Locale.Category category) {

        Properties props = GetPropertyAction.privilegedGetProperties();

        return getInstance(

            props.getProperty(category.languageKey,

                    defaultLocale.getLanguage()),

            props.getProperty(category.scriptKey,

                    defaultLocale.getScript()),

            props.getProperty(category.countryKey,

                    defaultLocale.getCountry()),

            props.getProperty(category.variantKey,

                    defaultLocale.getVariant()),

            getDefaultExtensions(props.getProperty(category.extensionsKey, ""))

                .orElse(defaultLocale.getLocaleExtensions()));

    }

    private static Optional<LocaleExtensions> getDefaultExtensions(String extensionsProp) {

        LocaleExtensions exts = null;

        try {

            exts = new InternalLocaleBuilder()

                .setExtensions(extensionsProp)

                .getLocaleExtensions();

        } catch (LocaleSyntaxException e) {

            // just ignore this incorrect property

        }

        return Optional.ofNullable(exts);

    }

    /**

     * Sets the default locale for this instance of the Java Virtual Machine.

     * This does not affect the host locale.

     * <p>

     * If there is a security manager, its <code>checkPermission</code>

     * method is called with a <code>PropertyPermission("user.language", "write")</code>

     * permission before the default locale is changed.

     * <p>

     * The Java Virtual Machine sets the default locale during startup

     * based on the host environment. It is used by many locale-sensitive

     * methods if no locale is explicitly specified.

     * <p>

     * Since changing the default locale may affect many different areas

     * of functionality, this method should only be used if the caller

     * is prepared to reinitialize locale-sensitive code running

     * within the same Java Virtual Machine.

     * <p>

     * By setting the default locale with this method, all of the default

     * locales for each Category are also set to the specified default locale.

     *

     * @throws SecurityException

     *        if a security manager exists and its

     *        <code>checkPermission</code> method doesn't allow the operation.

     * @throws NullPointerException if <code>newLocale</code> is null

     * @param newLocale the new default locale

     * @see SecurityManager#checkPermission

     * @see java.util.PropertyPermission

     */

    public static synchronized void setDefault(Locale newLocale) {

        setDefault(Category.DISPLAY, newLocale);

        setDefault(Category.FORMAT, newLocale);

        defaultLocale = newLocale;

    }

    /**

     * Sets the default locale for the specified Category for this instance

     * of the Java Virtual Machine. This does not affect the host locale.

     * <p>

     * If there is a security manager, its checkPermission method is called

     * with a PropertyPermission("user.language", "write") permission before

     * the default locale is changed.

     * <p>

     * The Java Virtual Machine sets the default locale during startup based

     * on the host environment. It is used by many locale-sensitive methods

     * if no locale is explicitly specified.

     * <p>

     * Since changing the default locale may affect many different areas of

     * functionality, this method should only be used if the caller is

     * prepared to reinitialize locale-sensitive code running within the

     * same Java Virtual Machine.

     *

     * @param category - the specified category to set the default locale

     * @param newLocale - the new default locale

     * @throws SecurityException if a security manager exists and its

     *     checkPermission method doesn't allow the operation.

     * @throws NullPointerException if category and/or newLocale is null

     * @see SecurityManager#checkPermission(java.security.Permission)

     * @see PropertyPermission

     * @see #getDefault(Locale.Category)

     * @since 1.7

     */

    public static synchronized void setDefault(Locale.Category category,

        Locale newLocale) {

        if (category == null)

            throw new NullPointerException("Category cannot be NULL");

        if (newLocale == null)

            throw new NullPointerException("Can't set default locale to NULL");

        SecurityManager sm = System.getSecurityManager();

        if (sm != null) sm.checkPermission(new PropertyPermission

                        ("user.language", "write"));

        switch (category) {

        case DISPLAY:

            defaultDisplayLocale = newLocale;

            break;

        case FORMAT:

            defaultFormatLocale = newLocale;

            break;

        default:

            assert false: "Unknown Category";

        }

    }

    /**

     * Returns an array of all installed locales.

     * The returned array represents the union of locales supported

     * by the Java runtime environment and by installed

     * {@link java.util.spi.LocaleServiceProvider LocaleServiceProvider}

     * implementations.  It must contain at least a <code>Locale</code>

     * instance equal to {@link java.util.Locale#US Locale.US}.

     *

     * @return An array of installed locales.

     */

    public static Locale[] getAvailableLocales() {

        return LocaleServiceProviderPool.getAllAvailableLocales();

    }

    /**

     * Returns a list of all 2-letter country codes defined in ISO 3166.

     * Can be used to create Locales.

     * This method is equivalent to {@link #getISOCountries(Locale.IsoCountryCode type)}

     * with {@code type}  {@link IsoCountryCode#PART1_ALPHA2}.

     * <p>

     * <b>Note:</b> The <code>Locale</code> class also supports other codes for

     * country (region), such as 3-letter numeric UN M.49 area codes.

     * Therefore, the list returned by this method does not contain ALL valid

     * codes that can be used to create Locales.

     * <p>

     * Note that this method does not return obsolete 2-letter country codes.

     * ISO3166-3 codes which designate country codes for those obsolete codes,

     * can be retrieved from {@link #getISOCountries(Locale.IsoCountryCode type)} with

     * {@code type}  {@link IsoCountryCode#PART3}.

     * @return An array of ISO 3166 two-letter country codes.

     */

    public static String[] getISOCountries() {

        if (isoCountries == null) {

            isoCountries = getISO2Table(LocaleISOData.isoCountryTable);

        }

        String[] result = new String[isoCountries.length];

        System.arraycopy(isoCountries, 0, result, 0, isoCountries.length);

        return result;

    }

    /**

     * Returns a {@code Set} of ISO3166 country codes for the specified type.

     *

     * @param type {@link Locale.IsoCountryCode} specified ISO code type.

     * @see java.util.Locale.IsoCountryCode

     * @throws NullPointerException if type is null

     * @return a {@code Set} of ISO country codes for the specified type.

     * @since 9

     */

    public static Set<String> getISOCountries(IsoCountryCode type) {

        Objects.requireNonNull(type);

        return IsoCountryCode.retrieveISOCountryCodes(type);

    }

    /**

     * Returns a list of all 2-letter language codes defined in ISO 639.

     * Can be used to create Locales.

     * <p>

     * <b>Note:</b>

     * <ul>

     * <li>ISO 639 is not a stable standard&mdash; some languages' codes have changed.

     * The list this function returns includes both the new and the old codes for the

     * languages whose codes have changed.

     * <li>The <code>Locale</code> class also supports language codes up to

     * 8 characters in length.  Therefore, the list returned by this method does

     * not contain ALL valid codes that can be used to create Locales.

     * </ul>

     *

     * @return An array of ISO 639 two-letter language codes.

     */

    public static String[] getISOLanguages() {

        if (isoLanguages == null) {

            isoLanguages = getISO2Table(LocaleISOData.isoLanguageTable);

        }

        String[] result = new String[isoLanguages.length];

        System.arraycopy(isoLanguages, 0, result, 0, isoLanguages.length);

        return result;

    }

    private static String[] getISO2Table(String table) {

        int len = table.length() / 5;

        String[] isoTable = new String[len];

        for (int i = 0, j = 0; i < len; i++, j += 5) {

            isoTable[i] = table.substring(j, j + 2);

        }

        return isoTable;

    }

    /**

     * Returns the language code of this Locale.

     *

     * <p><b>Note:</b> ISO 639 is not a stable standard&mdash; some languages' codes have changed.

     * Locale's constructor recognizes both the new and the old codes for the languages

     * whose codes have changed, but this function always returns the old code.  If you

     * want to check for a specific language whose code has changed, don't do

     * <pre>

     * if (locale.getLanguage().equals("he")) // BAD!

     *    ...

     * </pre>

     * Instead, do

     * <pre>

     * if (locale.getLanguage().equals(new Locale("he").getLanguage()))

     *    ...

     * </pre>

     * @return The language code, or the empty string if none is defined.

     * @see #getDisplayLanguage

     */

    public String getLanguage() {

        return baseLocale.getLanguage();

    }

    /**

     * Returns the script for this locale, which should

     * either be the empty string or an ISO 15924 4-letter script

     * code. The first letter is uppercase and the rest are

     * lowercase, for example, 'Latn', 'Cyrl'.

     *

     * @return The script code, or the empty string if none is defined.

     * @see #getDisplayScript

     * @since 1.7

     */

    public String getScript() {

        return baseLocale.getScript();

    }

    /**

     * Returns the country/region code for this locale, which should

     * either be the empty string, an uppercase ISO 3166 2-letter code,

     * or a UN M.49 3-digit code.

     *

     * @return The country/region code, or the empty string if none is defined.

     * @see #getDisplayCountry

     */

    public String getCountry() {

        return baseLocale.getRegion();

    }

    /**

     * Returns the variant code for this locale.

     *

     * @return The variant code, or the empty string if none is defined.

     * @see #getDisplayVariant

     */

    public String getVariant() {

        return baseLocale.getVariant();

    }

    /**

     * Returns {@code true} if this {@code Locale} has any <a href="#def_extensions">

     * extensions</a>.