Quelle Locale.java Sprache: JAVA

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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 jdk.internal.vm.annotation.Stable;

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} object represents a specific geographical, political,
* or cultural region. An operation that requires a {@code Locale} to perform
* its task is called <em>locale-sensitive</em> and uses the {@code Locale}
* 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="https://tools.ietf.org/html/rfc4647">RFC 4647 "Matching of Language
* Tags"</a> and <a href="https://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} 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} 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} 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} 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}.  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} 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} implement the semantics and syntax of BCP 47
*   extension subtags and private use subtags. The extensions are
*   case insensitive, but {@code Locale} 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]}.  Well-formed values have the form
*   {@code SUBTAG ('-' SUBTAG)*} 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} class
* does not provide any validation features.  The {@code Builder}
* 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.
*
* <h2><a id="def_locale_extension">Unicode locale/language extension</a></h2>
*
* <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} object contains Unicode locale
* attributes and keywords,
* {@code getExtension(UNICODE_LOCALE_EXTENSION)} will return a
* String representing this information, for example, "nu-thai".  The
* {@code Locale} 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.
*
* <h3><a id="ObtainingLocale">Obtaining a Locale</a></h3>
*
* <p>There are several ways to obtain a {@code Locale}
* object.
*
* <h4>Builder</h4>
*
* <p>Using {@link Builder} you can construct a {@code Locale} object
* that conforms to BCP 47 syntax.
*
* <h4>Factory Methods</h4>
*
* <p>The method {@link #forLanguageTag} obtains a {@code Locale}
* object for a well-formed BCP 47 language tag. The method
* {@link #of(String, String, String)} and its overloads obtain a
* {@code Locale} object from given {@code language}, {@code country},
* and/or {@code variant} defined above.
*
* <h4>Locale Constants</h4>
*
* <p>The {@code Locale} class provides a number of convenient constants
* that you can use to obtain {@code Locale} objects for commonly used
* locales. For example, {@code Locale.US} is the {@code Locale} object
* for the United States.
*
* <h3><a id="LocaleMatching">Locale Matching</a></h3>
*
* <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="https://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.
*
* <h4>Filtering</h4>
*
* <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.
*
* <h4>Lookup</h4>
*
* <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.
*
* <h3>Use of Locale</h3>
*
* <p>Once you've obtained a {@code Locale} you can query it for information
* about itself. Use {@code getCountry} to get the country (or region)
* code and {@code getLanguage} to get the language code.
* You can use {@code getDisplayCountry} to get the
* name of the country suitable for displaying to the user. Similarly,
* you can use {@code getDisplayLanguage} to get the name of
* the language suitable for displaying to the user. Interestingly,
* the {@code getDisplayXXX} 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} class formats
* numbers, currency, and percentages in a locale-sensitive manner. Classes
* such as {@code NumberFormat} have several convenience methods
* for creating a default object of that type. For example, the
* {@code NumberFormat} class provides these three convenience methods
* for creating a default {@code NumberFormat} 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} is the mechanism for identifying the kind of object
* ({@code NumberFormat}) 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.
*
* <h3>Compatibility</h3>
*
* <p>In order to maintain compatibility, Locale's
* constructors retain their behavior prior to the Java Runtime
* Environment version 1.7.  The same is largely true for the
* {@code toString} 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} 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} and {@code Locale.Builder} APIs instead.
* Clients desiring a string representation of the complete locale can
* then always rely on {@code toLanguageTag} for this purpose.
*
* <h4><a id="special_cases_constructor">Special cases</a></h4>
*
* <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.
*
* <h4>Serialization</h4>
*
* <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.
*
* <h4><a id="legacy_language_codes">Legacy language codes</a></h4>
*
* <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}. Since Java SE 17, this is no longer the case. Each
* language maps to its new form; {@code iw} maps to {@code he}, {@code ji}
* maps to {@code yi}, and {@code in} maps to {@code id}.
*
* <p>For the backward compatible behavior, the system property
* {@systemProperty java.locale.useOldISOCodes} reverts the behavior
* back to that of before Java SE 17. If the system property is set to
* {@code true}, those three current language codes are mapped to their
* backward compatible forms. The property is only read at Java runtime
* startup and subsequent calls to {@code System.setProperty()} will
* have no effect.
*
* <p>The APIs added in 1.7 map between the old and new language codes,
* maintaining the mapped codes internal to Locale (so that
* {@code getLanguage} and {@code toString} reflect the mapped
* code, which depends on the {@code java.locale.useOldISOCodes} system
* property), but using the new codes in the BCP 47 language tag APIs (so
* that {@code toLanguageTag} 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}.
*
* <h4>Three-letter language/country(region) codes</h4>
*
* <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 {

    /** Useful constant for language.
     */
    public static final Locale ENGLISH;

    /** Useful constant for language.
     */
    public static final Locale FRENCH;

    /** Useful constant for language.
     */
    public static final Locale GERMAN;

    /** Useful constant for language.
     */
    public static final Locale ITALIAN;

    /** Useful constant for language.
     */
    public static final Locale JAPANESE;

    /** Useful constant for language.
     */
    public static final Locale KOREAN;

    /** Useful constant for language.
     */
    public static final Locale CHINESE;

    /** Useful constant for language.
     */
    public static final Locale SIMPLIFIED_CHINESE;

    /** Useful constant for language.
     */
    public static final Locale TRADITIONAL_CHINESE;

    /** Useful constant for country.
     */
    public static final Locale FRANCE;

    /** Useful constant for country.
     */
    public static final Locale GERMANY;

    /** Useful constant for country.
     */
    public static final Locale ITALY;

    /** Useful constant for country.
     */
    public static final Locale JAPAN;

    /** Useful constant for country.
     */
    public static final Locale KOREA;

    /** Useful constant for country.
     */
    public static final Locale UK;

    /** Useful constant for country.
     */
    public static final Locale US;

    /** Useful constant for country.
     */
    public static final Locale CANADA;

    /** Useful constant for country.
     */
    public static final Locale CANADA_FRENCH;

    /**
     * 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;

    private static final Map<BaseLocale, Locale> CONSTANT_LOCALES = new HashMap<>();

    static {
        ENGLISH = createConstant(BaseLocale.ENGLISH);
        FRENCH = createConstant(BaseLocale.FRENCH);
        GERMAN = createConstant(BaseLocale.GERMAN);
        ITALIAN = createConstant(BaseLocale.ITALIAN);
        JAPANESE = createConstant(BaseLocale.JAPANESE);
        KOREAN = createConstant(BaseLocale.KOREAN);
        CHINESE = createConstant(BaseLocale.CHINESE);
        SIMPLIFIED_CHINESE = createConstant(BaseLocale.SIMPLIFIED_CHINESE);
        TRADITIONAL_CHINESE = createConstant(BaseLocale.TRADITIONAL_CHINESE);
        FRANCE = createConstant(BaseLocale.FRANCE);
        GERMANY = createConstant(BaseLocale.GERMANY);
        ITALY = createConstant(BaseLocale.ITALY);
        JAPAN = createConstant(BaseLocale.JAPAN);
        KOREA = createConstant(BaseLocale.KOREA);
        UK = createConstant(BaseLocale.UK);
        US = createConstant(BaseLocale.US);
        CANADA = createConstant(BaseLocale.CANADA);
        CANADA_FRENCH = createConstant(BaseLocale.CANADA_FRENCH);
        ROOT = createConstant(BaseLocale.ROOT);
    }

    /** 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;

    /**
     * This method must be called only for creating the Locale.*
     * constants due to making shortcuts.
     */
    private static Locale createConstant(byte baseType) {
        BaseLocale base = BaseLocale.constantBaseLocales[baseType];
        Locale locale = new Locale(base, null);
        CONSTANT_LOCALES.put(base, locale);
        return locale;
    }

    /**
     * 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
     */
    @java.io.Serial
    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 final 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.
     * @implNote
     * <ul>
     * <li>Obsolete ISO 639 codes ("iw", "ji", and "in") are mapped to
     * their current forms. See <a href="#legacy_language_codes">Legacy language
     * codes</a> for more information.
     * <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>
     *
     * @deprecated Locale constructors have been deprecated. See <a href ="#ObtainingLocale">
     * Obtaining a Locale</a> for other options.
     *
     * @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} 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} class description about valid country values.
     * @param variant Any arbitrary value used to indicate a variation of a {@code Locale}.
     * See the {@code Locale} class description for the details.
     * @throws    NullPointerException thrown if any argument is null.
     */
    @Deprecated(since="19")
    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.
     * @implNote
     * <ul>
     * <li>Obsolete ISO 639 codes ("iw", "ji", and "in") are mapped to
     * their current forms. See <a href="#legacy_language_codes">Legacy language
     * codes</a> for more information.
     * <li>For backward compatibility reasons, this constructor does not make
     * any syntactic checks on the input.
     * </ul>
     *
     * @deprecated Locale constructors have been deprecated. See <a href="#ObtainingLocale">
     * Obtaining a Locale</a> for other options.
     *
     * @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} 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} class description about valid country values.
     * @throws    NullPointerException thrown if either argument is null.
     */
    @Deprecated(since="19")
    public Locale(String language, String country) {
        this(language, country, "");
    }

    /**
     * Construct a locale from a language code.
     * This constructor normalizes the language value to lowercase.
     * @implNote
     * <ul>
     * <li>Obsolete ISO 639 codes ("iw", "ji", and "in") are mapped to
     * their current forms. See <a href="#legacy_language_codes">Legacy language
     * codes</a> for more information.
     * <li>For backward compatibility reasons, this constructor does not make
     * any syntactic checks on the input.
     * </ul>
     *
     * @deprecated Locale constructors have been deprecated. See <a href="#ObtainingLocale">
     * Obtaining a Locale</a> for other options.
     *
     * @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} class description about
     * valid language values.
     * @throws    NullPointerException thrown if argument is null.
     * @since 1.4
     */
    @Deprecated(since="19")
    public Locale(String language) {
        this(language, "", "");
    }

    /**
     * Obtains a locale from language, country and variant.
     * This method normalizes the language value to lowercase and
     * the country value to uppercase.
     * @implNote
     * <ul>
     * <li>This method does not make any syntactic checks on the input.
     * Use {@link Locale.Builder} for full syntactic checks with BCP47.
     * <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.
     * <li>Obsolete ISO 639 codes ("iw", "ji", and "in") are mapped to
     * their current forms. See <a href="#legacy_language_codes">Legacy language
     * codes</a> for more information.
     * </ul>
     *
     * @param language A language code. See the {@code Locale} class description of
     * <a href="#def_language">language</a> values.
     * @param country A country code. See the {@code Locale} class description of
     * <a href="#def_region">country</a> values.
     * @param variant Any arbitrary value used to indicate a variation of a {@code Locale}.
     * See the {@code Locale} class description of <a href="#def_variant">variant</a> values.
     * @throws    NullPointerException thrown if any argument is null.
     * @return A {@code Locale} object
     * @since 19
     */
    public static Locale of(String language, String country, String variant) {
        return getInstance(language, "", country, variant, null);
    }

    /**
     * Obtains a locale from language and country.
     * This method normalizes the language value to lowercase and
     * the country value to uppercase.
     * @implNote
     * <ul>
     * <li>This method does not make any syntactic checks on the input.
     * Use {@link Locale.Builder} for full syntactic checks with BCP47.
     * <li>Obsolete ISO 639 codes ("iw", "ji", and "in") are mapped to
     * their current forms. See <a href="#legacy_language_codes">Legacy language
     * codes</a> for more information.
     * </ul>
     *
     * @param language A language code. See the {@code Locale} class description of
     * <a href="#def_language">language</a> values.
     * @param country A country code. See the {@code Locale} class description of
     * <a href="#def_region">country</a> values.
     * @throws    NullPointerException thrown if either argument is null.
     * @return A {@code Locale} object
     * @since 19
     */
    public static Locale of(String language, String country) {
        return getInstance(language, "", country, "", null);
    }

    /**
     * Obtains a locale from a language code.
     * This method normalizes the language value to lowercase.
     * @implNote
     * <ul>
     * <li>This method does not make any syntactic checks on the input.
     * Use {@link Locale.Builder} for full syntactic checks with BCP47.
     * <li>Obsolete ISO 639 codes ("iw", "ji", and "in") are mapped to
     * their current forms. See <a href="#legacy_language_codes">Legacy language
     * codes</a> for more information.
     * </ul>
     *
     * @param language A language code. See the {@code Locale} class description of
     * <a href="#def_language">language</a> values.
     * @throws    NullPointerException thrown if argument is null.
     * @return A {@code Locale} object
     * @since 19
     */
    public static Locale of(String language) {
        return getInstance(language, "", "", "", null);
    }

    /**
     * Returns a {@code Locale} constructed from the given
     * {@code language}, {@code country} and
     * {@code variant}. If the same {@code Locale} instance
     * is available in the cache, then that instance is
     * returned. Otherwise, a new {@code Locale} 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} instance requested
     * @throws    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(convertOldISOCodes(language), script, country, variant);
        return getInstance(baseloc, extensions);
    }

    static Locale getInstance(BaseLocale baseloc, LocaleExtensions extensions) {
        if (extensions == null) {
            Locale locale = CONSTANT_LOCALES.get(baseloc);
            if (locale != null) {
                return locale;
            }
            return Cache.LOCALECACHE.get(baseloc);
        } else {
            LocaleKey key = new LocaleKey(baseloc, extensions);
            return Cache.LOCALECACHE.get(key);
        }
    }

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

        private static final Cache LOCALECACHE = new Cache();

        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 other)) {
                return false;
            }
            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
        Objects.requireNonNull(category);
        if (category == Category.DISPLAY) {
            Locale loc = defaultDisplayLocale; // volatile read
            if (loc == null) {
                loc = getDisplayLocale();
            }
            return loc;
        } else {
            assert category == Category.FORMAT : "Unknown category";
            Locale loc = defaultFormatLocale; // volatile read
            if (loc == null) {
                loc = getFormatLocale();
            }
            return loc;
        }
    }

    private static synchronized Locale getDisplayLocale() {
        Locale loc = defaultDisplayLocale;
        if (loc == null) {
            loc = defaultDisplayLocale = initDefault(Category.DISPLAY);
        }
        return loc;
    }

    private static synchronized Locale getFormatLocale() {
        Locale loc = defaultFormatLocale;
        if (loc == null) {
            loc = defaultFormatLocale = initDefault(Category.FORMAT);
        }
        return loc;
    }

    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();

        Locale locale = Locale.defaultLocale;
        return getInstance(
            props.getProperty(category.languageKey,
                    locale.getLanguage()),
            props.getProperty(category.scriptKey,
                    locale.getScript()),
            props.getProperty(category.countryKey,
                    locale.getCountry()),
            props.getProperty(category.variantKey,
                    locale.getVariant()),
            getDefaultExtensions(props.getProperty(category.extensionsKey, ""))
                .orElse(locale.getLocaleExtensions()));
    }

    private static Optional<LocaleExtensions> getDefaultExtensions(String extensionsProp) {
        if (LocaleUtils.isEmpty(extensionsProp)) {
            return Optional.empty();
        }

        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}
     * method is called with a {@code 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.
     * <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} method doesn't allow the operation.
     * @throws NullPointerException if {@code newLocale} 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");

        @SuppressWarnings("removal")
        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. At a minimum, the returned array must contain a
     * {@code Locale} instance equal to {@link Locale#ROOT Locale.ROOT} and
     * a {@code Locale} instance equal to {@link 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 obtain 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} 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 obtain 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 obtain Locales.
     * <p>
     * <b>Note:</b>
     * <ul>
     * <li>ISO 639 is not a stable standard— 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} 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 obtain Locales.
     * </ul>
     *
     * @return An array of ISO 639 two-letter language codes.
     */
    public static String[] getISOLanguages() {
        String[] languages = Locale.isoLanguages;
        if (languages == null) {
            Locale.isoLanguages = languages = getISO2Table(LocaleISOData.isoLanguageTable);
        }
        String[] result = new String[languages.length];
        System.arraycopy(languages, 0, result, 0, languages.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.
     *
     * @implNote This method returns the new forms for the obsolete ISO 639
     * codes ("iw", "ji", and "in"). See <a href="#legacy_language_codes">
     * Legacy language codes</a> for more information.
     *
     * @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>.
     *
     * @return {@code true} if this {@code Locale} has any extensions
     * @since 1.8
     */
    public boolean hasExtensions() {
        return localeExtensions != null;
    }

    /**
     * Returns a copy of this {@code Locale} with no <a href="#def_extensions">
     * extensions</a>. If this {@code Locale} has no extensions, this {@code Locale}
     * is returned.
     *
     * @return a copy of this {@code Locale} with no extensions, or {@code this}
     *         if {@code this} has no extensions
     * @since 1.8
     */
    public Locale stripExtensions() {
        return hasExtensions() ? Locale.getInstance(baseLocale, null) : this;
    }

    /**
     * Returns the extension (or private use) value associated with
     * the specified key, or null if there is no extension
     * associated with the key. To be well-formed, the key must be one
     * of {@code [0-9A-Za-z]}. Keys are case-insensitive, so
     * for example 'z' and 'Z' represent the same extension.
     *
     * @param key the extension key
     * @return The extension, or null if this locale defines no
     * extension for the specified key.
     * @throws IllegalArgumentException if key is not well-formed
     * @see #PRIVATE_USE_EXTENSION
     * @see #UNICODE_LOCALE_EXTENSION
     * @since 1.7
     */
    public String getExtension(char key) {
        if (!LocaleExtensions.isValidKey(key)) {
            throw new IllegalArgumentException("Ill-formed extension key: " + key);
        }
        return hasExtensions() ? localeExtensions.getExtensionValue(key) : null;
    }

    /**
     * Returns the set of extension keys associated with this locale, or the
     * empty set if it has no extensions. The returned set is unmodifiable.
     * The keys will all be lower-case.
     *
     * @return The set of extension keys, or the empty set if this locale has
     * no extensions.
     * @since 1.7
     */
    public Set<Character> getExtensionKeys() {
        if (!hasExtensions()) {
            return Collections.emptySet();
        }
        return localeExtensions.getKeys();
    }

    /**
     * Returns the set of unicode locale attributes associated with
     * this locale, or the empty set if it has no attributes. The
     * returned set is unmodifiable.
     *
     * @return The set of attributes.
     * @since 1.7
     */
    public Set<String> getUnicodeLocaleAttributes() {
        if (!hasExtensions()) {
            return Collections.emptySet();
        }
        return localeExtensions.getUnicodeLocaleAttributes();
    }

    /**
     * Returns the Unicode locale type associated with the specified Unicode locale key
     * for this locale. Returns the empty string for keys that are defined with no type.
     * Returns null if the key is not defined. Keys are case-insensitive. The key must
     * be two alphanumeric characters ([0-9a-zA-Z]), or an IllegalArgumentException is
     * thrown.
     *
     * @param key the Unicode locale key
     * @return The Unicode locale type associated with the key, or null if the
     * locale does not define the key.
     * @throws IllegalArgumentException if the key is not well-formed
     * @throws NullPointerException if {@code key} is null
     * @since 1.7
     */
    public String getUnicodeLocaleType(String key) {
        if (!isUnicodeExtensionKey(key)) {
            throw new IllegalArgumentException("Ill-formed Unicode locale key: " + key);
        }
        return hasExtensions() ? localeExtensions.getUnicodeLocaleType(key) : null;
    }

    /**
     * Returns the set of Unicode locale keys defined by this locale, or the empty set if
     * this locale has none.  The returned set is immutable.  Keys are all lower case.
     *
     * @return The set of Unicode locale keys, or the empty set if this locale has
     * no Unicode locale keywords.
     * @since 1.7
     */
    public Set<String> getUnicodeLocaleKeys() {
        if (localeExtensions == null) {
            return Collections.emptySet();
        }
        return localeExtensions.getUnicodeLocaleKeys();
    }

    /**
     * Package locale method returning the Locale's BaseLocale,
     * used by ResourceBundle
     * @return base locale of this Locale
     */
    BaseLocale getBaseLocale() {
        return baseLocale;
    }

    /**
     * Package private method returning the Locale's LocaleExtensions,
     * used by ResourceBundle.
     * @return locale extensions of this Locale,
     *         or {@code null} if no extensions are defined
     */
     LocaleExtensions getLocaleExtensions() {
         return localeExtensions;
     }

    /**
     * Returns a string representation of this {@code Locale}
     * object, consisting of language, country, variant, script,
     * and extensions as below:
     * <blockquote>
     * language + "_" + country + "_" + (variant + "_#" | "#") + script + "_" + extensions
     * </blockquote>
     *
     * Language is always lower case, country is always upper case, script is always title
     * case, and extensions are always lower case.  Extensions and private use subtags
     * will be in canonical order as explained in {@link #toLanguageTag}.
     *
     * <p>When the locale has neither script nor extensions, the result is the same as in
     * Java 6 and prior.
     *
     * <p>If both the language and country fields are missing, this function will return
     * the empty string, even if the variant, script, or extensions field is present (you
     * can't have a locale with just a variant, the variant must accompany a well-formed
     * language or country code).
     *
     * <p>If script or extensions are present and variant is missing, no underscore is
     * added before the "#".
     *
     * <p>This behavior is designed to support debugging and to be compatible with
     * previous uses of {@code toString} that expected language, country, and variant
     * fields only.  To represent a Locale as a String for interchange purposes, use
     * {@link #toLanguageTag}.
     *
     * <p>Examples: <ul>
     * <li>{@code en}</li>
     * <li>{@code de_DE}</li>
     * <li>{@code _GB}</li>
     * <li>{@code en_US_WIN}</li>
     * <li>{@code de__POSIX}</li>
     * <li>{@code zh_CN_#Hans}</li>
     * <li>{@code zh_TW_#Hant_x-java}</li>
     * <li>{@code th_TH_TH_#u-nu-thai}</li></ul>
     *
     * @return A string representation of the Locale, for debugging.
     * @see #getDisplayName
     * @see #toLanguageTag
     */
    @Override
    public final String toString() {
        boolean l = !baseLocale.getLanguage().isEmpty();
        boolean s = !baseLocale.getScript().isEmpty();
        boolean r = !baseLocale.getRegion().isEmpty();
        boolean v = !baseLocale.getVariant().isEmpty();
        boolean e = localeExtensions != null && !localeExtensions.getID().isEmpty();

        StringBuilder result = new StringBuilder(baseLocale.getLanguage());
        if (r || (l && (v || s || e))) {
            result.append('_')
                .append(baseLocale.getRegion()); // This may just append '_'
        }
        if (v && (l || r)) {
            result.append('_')
                .append(baseLocale.getVariant());
        }

        if (s && (l || r)) {
            result.append("_#")
                .append(baseLocale.getScript());
        }

        if (e && (l || r)) {
            result.append('_');
            if (!s) {
                result.append('#');
            }
            result.append(localeExtensions.getID());
        }

        return result.toString();
    }

    /**
     * Returns a well-formed IETF BCP 47 language tag representing
     * this locale.
     *
     * <p>If this {@code Locale} has a language, country, or
     * variant that does not satisfy the IETF BCP 47 language tag
     * syntax requirements, this method handles these fields as
     * described below:
     *
     * <p><b>Language:</b> If language is empty, or not <a
     * href="#def_language" >well-formed</a> (for example "a" or
     * "e2"), it will be emitted as "und" (Undetermined).
     *
     * <p><b>Country:</b> If country is not <a
     * href="#def_region">well-formed</a> (for example "12" or "USA"),
     * it will be omitted.
     *
     * <p><b>Variant:</b> If variant <b>is</b> <a
     * href="#def_variant">well-formed</a>, each sub-segment
     * (delimited by '-' or '_') is emitted as a subtag.  Otherwise:
     * <ul>
     *
     * <li>if all sub-segments match <code>[0-9a-zA-Z]{1,8}</code>
     * (for example "WIN" or "Oracle_JDK_Standard_Edition"), the first
     * ill-formed sub-segment and all following will be appended to
     * the private use subtag.  The first appended subtag will be
     * "lvariant", followed by the sub-segments in order, separated by
     * hyphen. For example, "x-lvariant-WIN",
     * "Oracle-x-lvariant-JDK-Standard-Edition".
     *
     * <li>if any sub-segment does not match
     * <code>[0-9a-zA-Z]{1,8}</code>, the variant will be truncated
     * and the problematic sub-segment and all following sub-segments
     * will be omitted.  If the remainder is non-empty, it will be
     * emitted as a private use subtag as above (even if the remainder
     * turns out to be well-formed).  For example,
     * "Solaris_isjustthecoolestthing" is emitted as
     * "x-lvariant-Solaris", not as "solaris".</li></ul>
     *
     * <p><b>Special Conversions:</b> Java supports some old locale
     * representations, including deprecated ISO language codes,
     * for compatibility. This method performs the following
     * conversions:
     * <ul>
     *
     * <li>Deprecated ISO language codes "iw", "ji", and "in" are
     * converted to "he", "yi", and "id", respectively.
     *
     * <li>A locale with language "no", country "NO", and variant
     * "NY", representing Norwegian Nynorsk (Norway), is converted
     * to a language tag "nn-NO".</li></ul>
     *
     * <p><b>Note:</b> Although the language tag obtained by this
     * method is well-formed (satisfies the syntax requirements
     * defined by the IETF BCP 47 specification), it is not
     * necessarily a valid BCP 47 language tag.  For example,
     * <pre>
     *   Locale.forLanguageTag("xx-YY").toLanguageTag();</pre>
     *
     * will return "xx-YY", but the language subtag "xx" and the
     * region subtag "YY" are invalid because they are not registered
     * in the IANA Language Subtag Registry.
     *
     * @return a BCP47 language tag representing the locale
     * @see #forLanguageTag(String)
     * @since 1.7
     */
    public String toLanguageTag() {
        String lTag = this.languageTag;
        if (lTag != null) {
            return lTag;
        }

        LanguageTag tag = LanguageTag.parseLocale(baseLocale, localeExtensions);
        StringBuilder buf = new StringBuilder();

        String subtag = tag.getLanguage();
        if (!subtag.isEmpty()) {
            buf.append(LanguageTag.canonicalizeLanguage(subtag));
        }

        subtag = tag.getScript();
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