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   * Copyright (C) 2014 The Android Open Source Project
   * Copyright (c) 1996, 2014, 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 com.android.icu.util.LocaleNative;
  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 libcore.icu.ICU;
  
  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;
  
  // Android-added: documentation about ICU data & warning of default locale.
  
  /**
   * 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&mdash; 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 name="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 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 name="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 name="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 name="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 name="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 name="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".code
   *
   * <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 name="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 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 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 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 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 name="special_cases_constructor">Special cases</a></h5>
   *
   * <p>For compatibility reasons, two
   * non-conforming locales are treated as special cases.  These are
   * <b><tt>ja_JP_JP</tt></b> and <b><tt>th_TH_TH</tt></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 <tt>ja_JP_JP</tt> 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 <tt>ca</tt> (for "calendar") and type
   * <tt>japanese</tt>. When the Locale constructor is called with the
   * arguments "ja", "JP", "JP", the extension "u-ca-japanese" is
   * automatically added.
   *
   * <p>Java has used <tt>th_TH_TH</tt> 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
   * <tt>nu</tt> (for "number") and value <tt>thai</tt>. 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: <tt>he</tt> maps to <tt>iw</tt>,
   * <tt>yi</tt> maps to <tt>ji</tt>, and <tt>id</tt> maps to
   * <tt>in</tt>.  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.
   *
   * <a name="locale_data"></a><h4>Locale data</h4>
   * <p>Note that locale data comes solely from ICU. User-supplied locale service providers (using
   * the {@code java.text.spi} or {@code java.util.spi} mechanisms) are not supported.
   *
   * <p>Here are the versions of ICU (and the corresponding CLDR and Unicode versions) used in
   * various Android releases:
   * <table BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY="">
   * <tr><td>Android 1.5 (Cupcake)/Android 1.6 (Donut)/Android 2.0 (Eclair)</td>
   *     <td>ICU 3.8</td>
   *     <td><a href="http://cldr.unicode.org/index/downloads/cldr-1-5">CLDR 1.5</a></td>
   *     <td><a href="http://www.unicode.org/versions/Unicode5.0.0/">Unicode 5.0</a></td></tr>
   * <tr><td>Android 2.2 (Froyo)</td>
   *     <td>ICU 4.2</td>
   *     <td><a href="http://cldr.unicode.org/index/downloads/cldr-1-7">CLDR 1.7</a></td>
   *     <td><a href="http://www.unicode.org/versions/Unicode5.1.0/">Unicode 5.1</a></td></tr>
   * <tr><td>Android 2.3 (Gingerbread)/Android 3.0 (Honeycomb)</td>
   *     <td>ICU 4.4</td>
   *     <td><a href="http://cldr.unicode.org/index/downloads/cldr-1-8">CLDR 1.8</a></td>
   *     <td><a href="http://www.unicode.org/versions/Unicode5.2.0/">Unicode 5.2</a></td></tr>
   * <tr><td>Android 4.0 (Ice Cream Sandwich)</td>
   *     <td><a href="http://site.icu-project.org/download/46">ICU 4.6</a></td>
   *     <td><a href="http://cldr.unicode.org/index/downloads/cldr-1-9">CLDR 1.9</a></td>
   *     <td><a href="http://www.unicode.org/versions/Unicode6.0.0/">Unicode 6.0</a></td></tr>
   * <tr><td>Android 4.1 (Jelly Bean)</td>
   *     <td><a href="http://site.icu-project.org/download/48">ICU 4.8</a></td>
   *     <td><a href="http://cldr.unicode.org/index/downloads/cldr-2-0">CLDR 2.0</a></td>
   *     <td><a href="http://www.unicode.org/versions/Unicode6.0.0/">Unicode 6.0</a></td></tr>
   * <tr><td>Android 4.3 (Jelly Bean MR2)</td>
   *     <td><a href="http://site.icu-project.org/download/50">ICU 50</a></td>
   *     <td><a href="http://cldr.unicode.org/index/downloads/cldr-22-1">CLDR 22.1</a></td>
   *     <td><a href="http://www.unicode.org/versions/Unicode6.2.0/">Unicode 6.2</a></td></tr>
   * <tr><td>Android 4.4 (KitKat)</td>
   *     <td><a href="http://site.icu-project.org/download/51">ICU 51</a></td>
   *     <td><a href="http://cldr.unicode.org/index/downloads/cldr-23">CLDR 23</a></td>
   *     <td><a href="http://www.unicode.org/versions/Unicode6.2.0/">Unicode 6.2</a></td></tr>
   * <tr><td>Android 5.0 (Lollipop)</td>
   *     <td><a href="http://site.icu-project.org/download/53">ICU 53</a></td>
   *     <td><a href="http://cldr.unicode.org/index/downloads/cldr-25">CLDR 25</a></td>
   *     <td><a href="http://www.unicode.org/versions/Unicode6.3.0/">Unicode 6.3</a></td></tr>
   * <tr><td>Android 6.0 (Marshmallow)</td>
   *     <td><a href="http://site.icu-project.org/download/55">ICU 55.1</a></td>
   *     <td><a href="http://cldr.unicode.org/index/downloads/cldr-27">CLDR 27.0.1</a></td>
   *     <td><a href="http://www.unicode.org/versions/Unicode7.0.0/">Unicode 7.0</a></td></tr>
   * <tr><td>Android 7.0 (Nougat)</td>
   *     <td><a href="http://site.icu-project.org/download/56">ICU 56.1</a></td>
   *     <td><a href="http://cldr.unicode.org/index/downloads/cldr-28">CLDR 28</a></td>
   *     <td><a href="http://www.unicode.org/versions/Unicode8.0.0/">Unicode 8.0</a></td></tr>
   * <tr><td>Android 8.0 (Oreo)</td>
   *     <td><a href="http://site.icu-project.org/download/58">ICU 58.2</a></td>
   *     <td><a href="http://cldr.unicode.org/index/downloads/cldr-30">CLDR 30.0.3</a></td>
   *     <td><a href="http://www.unicode.org/versions/Unicode9.0.0/">Unicode 9.0</a></td></tr>
   * <tr><td>Android 9.0 (Pie)</td>
   *     <td><a href="http://site.icu-project.org/download/60">ICU 60.2</a></td>
   *     <td><a href="http://cldr.unicode.org/index/downloads/cldr-32">CLDR 32.0.1</a></td>
   *     <td><a href="http://www.unicode.org/versions/Unicode10.0.0/">Unicode 10.0</a></td></tr>
   * <tr><td>Android 10.0 (Q)</td>
   *     <td><a href="http://site.icu-project.org/download/63">ICU 63.2</a></td>
   *     <td><a href="http://cldr.unicode.org/index/downloads/cldr-34">CLDR 34</a></td>
   *     <td><a href="http://www.unicode.org/versions/Unicode11.0.0/">Unicode 11.0</a></td></tr>
   * </table>
   *
   * <a name="default_locale"></a><h4>Be wary of the default locale</h3>
   * <p>Note that there are many convenience methods that automatically use the default locale, but
   * using them may lead to subtle bugs.
   *
   * <p>The default locale is appropriate for tasks that involve presenting data to the user. In
   * this case, you want to use the user's date/time formats, number
   * formats, rules for conversion to lowercase, and so on. In this case, it's safe to use the
   * convenience methods.
   *
   * <p>The default locale is <i>not</i> appropriate for machine-readable output. The best choice
   * there is usually {@code Locale.US}&nbsp;&ndash; this locale is guaranteed to be available on all
   * devices, and the fact that it has no surprising special cases and is frequently used (especially
   * for computer-computer communication) means that it tends to be the most efficient choice too.
   *
   * <p>A common mistake is to implicitly use the default locale when producing output meant to be
   * machine-readable. This tends to work on the developer's test devices (especially because so many
   * developers use en_US), but fails when run on a device whose user is in a more complex locale.
   *
   * <p>For example, if you're formatting integers some locales will use non-ASCII decimal
   * digits. As another example, if you're formatting floating-point numbers some locales will use
   * {@code ','} as the decimal point and {@code '.'} for digit grouping. That's correct for
   * human-readable output, but likely to cause problems if presented to another
   * computer ({@link Double#parseDouble} can't parse such a number, for example).
   * You should also be wary of the {@link String#toLowerCase} and
   * {@link String#toUpperCase} overloads that don't take a {@code Locale}: in Turkey, for example,
   * the characters {@code 'i'} and {@code 'I'} won't be converted to {@code 'I'} and {@code 'i'}.
   * This is the correct behavior for Turkish text (such as user input), but inappropriate for, say,
   * HTTP headers.
   *
   * @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 {
  
      static private final  Cache LOCALECACHE = new Cache();
  
      /** Useful constant for language.
       */
      static public final Locale ENGLISH = createConstant("en", "");
  
      /** Useful constant for language.
       */
      static public final Locale FRENCH = createConstant("fr", "");
  
      /** Useful constant for language.
       */
      static public final Locale GERMAN = createConstant("de", "");
  
      /** Useful constant for language.
       */
      static public final Locale ITALIAN = createConstant("it", "");
  
      /** Useful constant for language.
       */
      static public final Locale JAPANESE = createConstant("ja", "");
  
      /** Useful constant for language.
       */
      static public final Locale KOREAN = createConstant("ko", "");
  
      /** Useful constant for language.
       */
      static public final Locale CHINESE = createConstant("zh", "");
  
      /** Useful constant for language.
       */
      static public final Locale SIMPLIFIED_CHINESE = createConstant("zh", "CN");
  
      /** Useful constant for language.
       */
      static public final Locale TRADITIONAL_CHINESE = createConstant("zh", "TW");
  
      /** Useful constant for country.
       */
      static public final Locale FRANCE = createConstant("fr", "FR");
  
      /** Useful constant for country.
       */
      static public final Locale GERMANY = createConstant("de", "DE");
  
      /** Useful constant for country.
       */
      static public final Locale ITALY = createConstant("it", "IT");
  
      /** Useful constant for country.
       */
      static public final Locale JAPAN = createConstant("ja", "JP");
  
      /** Useful constant for country.
       */
      static public final Locale KOREA = createConstant("ko", "KR");
  
      /** Useful constant for country.
       */
      static public final Locale CHINA = SIMPLIFIED_CHINESE;
  
      /** Useful constant for country.
       */
      static public final Locale PRC = SIMPLIFIED_CHINESE;
  
      /** Useful constant for country.
       */
      static public final Locale TAIWAN = TRADITIONAL_CHINESE;
  
      /** Useful constant for country.
       */
      static public final Locale UK = createConstant("en", "GB");
  
      /** Useful constant for country.
       */
      static public final Locale US = createConstant("en", "US");
  
      /** Useful constant for country.
       */
      static public final Locale CANADA = createConstant("en", "CA");
  
      /** Useful constant for country.
       */
      static public final Locale CANADA_FRENCH = createConstant("fr", "CA");
  
      // Android-added: (internal only): ISO 639-3 generic code for undetermined languages.
      private static final String UNDETERMINED_LANGUAGE = "und";
  
      /**
       * 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
       */
      static public final Locale ROOT = createConstant("", "");
  
      /**
       * The key for the private use extension ('x').
       *
       * @see #getExtension(char)
       * @see Builder#setExtension(char, String)
       * @since 1.7
       */
      static public final char PRIVATE_USE_EXTENSION = 'x';
  
      /**
       * The key for Unicode locale extension ('u').
       *
       * @see #getExtension(char)
       * @see Builder#setExtension(char, String)
       * @since 1.7
       */
      static public final char UNICODE_LOCALE_EXTENSION = 'u';
  
      /** serialization ID
       */
      static final long serialVersionUID = 9149081749638150636L;
  
      /**
       * 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 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 numric-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) {
          LocaleKey key = new LocaleKey(baseloc, extensions);
          return LOCALECACHE.get(key);
      }
  
      private static class Cache extends LocaleObjectCache<LocaleKey, Locale> {
          private Cache() {
          }
  
          @Override
          protected Locale createObject(LocaleKey key) {
              return new Locale(key.base, key.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(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
          // Android-changed: Add NoImagePreloadHolder to allow compile-time initialization.
          // return defaultLocale;
          return NoImagePreloadHolder.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(Category, Locale)
       * @since 1.7
       */
      public static Locale getDefault(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();
      }
  
      /**
       * @hide visible for testing.
       */
      // Android-changed: Make initDefault() @hide public for testing.
      // private static Locale initDefault() {
      public static Locale initDefault() {
          // BEGIN Android-added: In initDefault(), prioritize user.locale.
          // user.locale gets priority
          final String languageTag = System.getProperty("user.locale", "");
          if (!languageTag.isEmpty()) {
              return Locale.forLanguageTag(languageTag);
          }
          // END Android-added: In initDefault(), prioritize user.locale.
  
          // BEGIN Android-changed: Short-circuit legacy security code.
          // Use System.getProperty(name, default) instead of
          // AccessController.doPrivileged(new GetPropertyAction(name, default)).
          String language, region, script, country, variant;
          language = System.getProperty("user.language", "en");
          // for compatibility, check for old user.region property
          region = System.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 = System.getProperty("user.script", "");
              country = System.getProperty("user.country", "");
              variant = System.getProperty("user.variant", "");
          }
          // END Android-changed: Short-circuit legacy security code.
  
          return getInstance(language, script, country, variant, null);
      }
  
      private static Locale initDefault(Category category) {
          // Android-added: Add NoImagePreloadHolder to allow compile-time initialization.
          final Locale defaultLocale = NoImagePreloadHolder.defaultLocale;
          // BEGIN Android-changed: Short-circuit legacy security code.
          /*
          return getInstance(
              AccessController.doPrivileged(
                  new GetPropertyAction(category.languageKey, defaultLocale.getLanguage())),
              AccessController.doPrivileged(
                  new GetPropertyAction(category.scriptKey, defaultLocale.getScript())),
              AccessController.doPrivileged(
                  new GetPropertyAction(category.countryKey, defaultLocale.getCountry())),
              AccessController.doPrivileged(
                  new GetPropertyAction(category.variantKey, defaultLocale.getVariant())),
              null);
          */
          return getInstance(
              System.getProperty(category.languageKey, defaultLocale.getLanguage()),
              System.getProperty(category.scriptKey, defaultLocale.getScript()),
              System.getProperty(category.countryKey, defaultLocale.getCountry()),
              System.getProperty(category.variantKey, defaultLocale.getVariant()),
              null);
          // END Android-changed: Short-circuit legacy security code.
      }
  
      /**
       * 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 PropertyPermission
       */
      public static synchronized void setDefault(Locale newLocale) {
          setDefault(Category.DISPLAY, newLocale);
          setDefault(Category.FORMAT, newLocale);
          // Android-changed: Add NoImagePreloadHolder to allow compile-time initialization.
          // defaultLocale = newLocale;
          NoImagePreloadHolder.defaultLocale = newLocale;
          // Android-added: Keep ICU state in sync with java.util.
          ICU.setDefaultLocale(newLocale.toLanguageTag());
      }
  
      /**
       * 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.
       * <p>
       *
       * @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(Category)
       * @since 1.7
       */
      public static synchronized void setDefault(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";
          }
      }
  
      // Android-changed: Removed documentation references to LocaleServiceProvider.
      /**
       * Returns an array of all installed locales.
       *
       * @return An array of installed locales.
       */
      public static Locale[] getAvailableLocales() {
          // Android-changed: Use ICU.
          // return LocaleServiceProviderPool.getAllAvailableLocales();
          return ICU.getAvailableLocales();
      }
  
      /**
       * Returns a list of all 2-letter country codes defined in ISO 3166.
       * Can be used to create Locales.
       * <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.
       *
       * @return An array of ISO 3166 two-letter country codes.
       */
      public static String[] getISOCountries() {
          // Android-changed: Use ICU.
          /*
          if (isoCountries == null) {
              isoCountries = getISO2Table(LocaleISOData.isoCountryTable);
          }
          String[] result = new String[isoCountries.length];
          System.arraycopy(isoCountries, 0, result, 0, isoCountries.length);
          return result;
          */
          return ICU.getISOCountries();
      }
  
      /**
       * 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 Am array of ISO 639 two-letter language codes.
       */
      public static String[] getISOLanguages() {
          // Android-changed: Use ICU.
          /*
          if (isoLanguages == null) {
              isoLanguages = getISO2Table(LocaleISOData.isoLanguageTable);
          }
          String[] result = new String[isoLanguages.length];
          System.arraycopy(isoLanguages, 0, result, 0, isoLanguages.length);
          return result;
          */
          return ICU.getISOLanguages();
      }
  
      // Android-removed: Use ICU.
      // Private helper method getISO2Table(), unused on Android.
      /*
      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>.
       *
       * @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]</code>. 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</code> 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 exnteions of this Locale,
       *         or {@code null} if no extensions are defined
       */
       LocaleExtensions getLocaleExtensions() {
           return localeExtensions;
       }
  
      /**
       * Returns a string representation of this <code>Locale</code>
       * 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</code> 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><tt>en</tt></li>
       * <li><tt>de_DE</tt></li>
       * <li><tt>_GB</tt></li>
       * <li><tt>en_US_WIN</tt></li>
       * <li><tt>de__POSIX</tt></li>
       * <li><tt>zh_CN_#Hans</tt></li>
       * <li><tt>zh_TW_#Hant-x-java</tt></li>
       * <li><tt>th_TH_TH_#u-nu-thai</tt></li></ul>
       *
       * @return A string representation of the Locale, for debugging.
       * @see #getDisplayName
       * @see #toLanguageTag
       */
      @Override
      public final String toString() {
          boolean l = (baseLocale.getLanguage().length() != 0);
          boolean s = (baseLocale.getScript().length() != 0);
          boolean r = (baseLocale.getRegion().length() != 0);
          boolean v = (baseLocale.getVariant().length() != 0);
          boolean e = (localeExtensions != null && localeExtensions.getID().length() != 0);
  
          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</code> 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 created 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>
       *   new Locale("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() {
          if (languageTag != null) {
              return languageTag;
          }
  
          LanguageTag tag = LanguageTag.parseLocale(baseLocale, localeExtensions);
          StringBuilder buf = new StringBuilder();
  
          String subtag = tag.getLanguage();
          if (subtag.length() > 0) {
              buf.append(LanguageTag.canonicalizeLanguage(subtag));
          }
  
          subtag = tag.getScript();
          if (subtag.length() > 0) {
              buf.append(LanguageTag.SEP);
              buf.append(LanguageTag.canonicalizeScript(subtag));
          }
  
          subtag = tag.getRegion();
          if (subtag.length() > 0) {
              buf.append(LanguageTag.SEP);
              buf.append(LanguageTag.canonicalizeRegion(subtag));
          }
  
          List<String>subtags = tag.getVariants();
          for (String s : subtags) {
              buf.append(LanguageTag.SEP);
              // preserve casing
              buf.append(s);
          }
  
          subtags = tag.getExtensions();
          for (String s : subtags) {
              buf.append(LanguageTag.SEP);
              buf.append(LanguageTag.canonicalizeExtension(s));
          }
  
          subtag = tag.getPrivateuse();
          if (subtag.length() > 0) {
              if (buf.length() > 0) {
                  buf.append(LanguageTag.SEP);
              }
              buf.append(LanguageTag.PRIVATEUSE).append(LanguageTag.SEP);
              // preserve casing
              buf.append(subtag);
          }
  
          String langTag = buf.toString();
          synchronized (this) {
              if (languageTag == null) {
                  languageTag = langTag;
              }
          }
          return languageTag;
      }
  
      /**
       * Returns a locale for the specified IETF BCP 47 language tag string.
       *
       * <p>If the specified language tag contains any ill-formed subtags,
       * the first such subtag and all following subtags are ignored.  Compare
       * to {@link Builder#setLanguageTag} which throws an exception
       * in this case.
       *
       * <p>The following <b>conversions</b> are performed:<ul>
       *
       * <li>The language code "und" is mapped to language "".
       *
       * <li>The language codes "he", "yi", and "id" are mapped to "iw",
       * "ji", and "in" respectively. (This is the same canonicalization
       * that's done in Locale's constructors.)
       *
       * <li>The portion of a private use subtag prefixed by "lvariant",
       * if any, is removed and appended to the variant field in the
       * result locale (without case normalization).  If it is then
       * empty, the private use subtag is discarded:
       *
       * <pre>
       *     Locale loc;
       *     loc = Locale.forLanguageTag("en-US-x-lvariant-POSIX");
       *     loc.getVariant(); // returns "POSIX"
       *     loc.getExtension('x'); // returns null
       *
       *     loc = Locale.forLanguageTag("de-POSIX-x-URP-lvariant-Abc-Def");
       *     loc.getVariant(); // returns "POSIX_Abc_Def"
       *     loc.getExtension('x'); // returns "urp"
       * </pre>
       *
       * <li>When the languageTag argument contains an extlang subtag,
       * the first such subtag is used as the language, and the primary
       * language subtag and other extlang subtags are ignored:
       *
       * <pre>
       *     Locale.forLanguageTag("ar-aao").getLanguage(); // returns "aao"
       *     Locale.forLanguageTag("en-abc-def-us").toString(); // returns "abc_US"
       * </pre>
       *
       * <li>Case is normalized except for variant tags, which are left
       * unchanged.  Language is normalized to lower case, script to
       * title case, country to upper case, and extensions to lower
       * case.
       *
       * <li>If, after processing, the locale would exactly match either
       * ja_JP_JP or th_TH_TH with no extensions, the appropriate
       * extensions are added as though the constructor had been called:
       *
       * <pre>
       *    Locale.forLanguageTag("ja-JP-x-lvariant-JP").toLanguageTag();
       *    // returns "ja-JP-u-ca-japanese-x-lvariant-JP"
       *    Locale.forLanguageTag("th-TH-x-lvariant-TH").toLanguageTag();
       *    // returns "th-TH-u-nu-thai-x-lvariant-TH"
       * </pre></ul>
       *
       * <p>This implements the 'Language-Tag' production of BCP47, and
       * so supports grandfathered (regular and irregular) as well as
       * private use language tags.  Stand alone private use tags are
       * represented as empty language and extension 'x-whatever',
       * and grandfathered tags are converted to their canonical replacements
       * where they exist.
       *
       * <p>Grandfathered tags with canonical replacements are as follows:
       *
       * <table summary="Grandfathered tags with canonical replacements">
       * <tbody align="center">
       * <tr><th>grandfathered tag</th><th>&nbsp;</th><th>modern replacement</th></tr>
       * <tr><td>art-lojban</td><td>&nbsp;</td><td>jbo</td></tr>
       * <tr><td>i-ami</td><td>&nbsp;</td><td>ami</td></tr>
       * <tr><td>i-bnn</td><td>&nbsp;</td><td>bnn</td></tr>
       * <tr><td>i-hak</td><td>&nbsp;</td><td>hak</td></tr>
       * <tr><td>i-klingon</td><td>&nbsp;</td><td>tlh</td></tr>
       * <tr><td>i-lux</td><td>&nbsp;</td><td>lb</td></tr>
       * <tr><td>i-navajo</td><td>&nbsp;</td><td>nv</td></tr>
       * <tr><td>i-pwn</td><td>&nbsp;</td><td>pwn</td></tr>
       * <tr><td>i-tao</td><td>&nbsp;</td><td>tao</td></tr>
       * <tr><td>i-tay</td><td>&nbsp;</td><td>tay</td></tr>
       * <tr><td>i-tsu</td><td>&nbsp;</td><td>tsu</td></tr>
       * <tr><td>no-bok</td><td>&nbsp;</td><td>nb</td></tr>
       * <tr><td>no-nyn</td><td>&nbsp;</td><td>nn</td></tr>
       * <tr><td>sgn-BE-FR</td><td>&nbsp;</td><td>sfb</td></tr>
       * <tr><td>sgn-BE-NL</td><td>&nbsp;</td><td>vgt</td></tr>
       * <tr><td>sgn-CH-DE</td><td>&nbsp;</td><td>sgg</td></tr>
       * <tr><td>zh-guoyu</td><td>&nbsp;</td><td>cmn</td></tr>
       * <tr><td>zh-hakka</td><td>&nbsp;</td><td>hak</td></tr>
       * <tr><td>zh-min-nan</td><td>&nbsp;</td><td>nan</td></tr>
       * <tr><td>zh-xiang</td><td>&nbsp;</td><td>hsn</td></tr>
       * </tbody>
       * </table>
       *
       * <p>Grandfathered tags with no modern replacement will be
       * converted as follows:
       *
       * <table summary="Grandfathered tags with no modern replacement">
       * <tbody align="center">
       * <tr><th>grandfathered tag</th><th>&nbsp;</th><th>converts to</th></tr>
       * <tr><td>cel-gaulish</td><td>&nbsp;</td><td>xtg-x-cel-gaulish</td></tr>
       * <tr><td>en-GB-oed</td><td>&nbsp;</td><td>en-GB-x-oed</td></tr>
       * <tr><td>i-default</td><td>&nbsp;</td><td>en-x-i-default</td></tr>
       * <tr><td>i-enochian</td><td>&nbsp;</td><td>und-x-i-enochian</td></tr>
       * <tr><td>i-mingo</td><td>&nbsp;</td><td>see-x-i-mingo</td></tr>
       * <tr><td>zh-min</td><td>&nbsp;</td><td>nan-x-zh-min</td></tr>
       * </tbody>
       * </table>
       *
       * <p>For a list of all grandfathered tags, see the
       * IANA Language Subtag Registry (search for "Type: grandfathered").
       *
       * <p><b>Note</b>: there is no guarantee that <code>toLanguageTag</code>
       * and <code>forLanguageTag</code> will round-trip.
       *
       * @param languageTag the language tag
       * @return The locale that best represents the language tag.
       * @throws NullPointerException if <code>languageTag</code> is <code>null</code>
       * @see #toLanguageTag()
       * @see Builder#setLanguageTag(String)
       * @since 1.7
       */
      public static Locale forLanguageTag(String languageTag) {
          LanguageTag tag = LanguageTag.parse(languageTag, null);
          InternalLocaleBuilder bldr = new InternalLocaleBuilder();
          bldr.setLanguageTag(tag);
          BaseLocale base = bldr.getBaseLocale();
          LocaleExtensions exts = bldr.getLocaleExtensions();
          if (exts == null && base.getVariant().length() > 0) {
              exts = getCompatibilityExtensions(base.getLanguage(), base.getScript(),
                                                base.getRegion(), base.getVariant());
          }
          return getInstance(base, exts);
      }
  
      /**
       * Returns a three-letter abbreviation of this locale's language.
       * If the language matches an ISO 639-1 two-letter code, the
       * corresponding ISO 639-2/T three-letter lowercase code is
       * returned.  The ISO 639-2 language codes can be found on-line,
       * see "Codes for the Representation of Names of Languages Part 2:
       * Alpha-3 Code".  If the locale specifies a three-letter
       * language, the language is returned as is.  If the locale does
       * not specify a language the empty string is returned.
       *
       * @return A three-letter abbreviation of this locale's language.
       * @exception MissingResourceException Throws MissingResourceException if
       * three-letter language abbreviation is not available for this locale.
       */
      public String getISO3Language() throws MissingResourceException {
          String lang = baseLocale.getLanguage();
          if (lang.length() == 3) {
              return lang;
          }
          // BEGIN Android-added: app compat: Use "" as ISO3 for empty languages.
          else if (lang.isEmpty()) {
              return "";
          }
          // END Android-added: app compat: Use "" as ISO3 for empty languages.
  
          // BEGIN Android-changed: Use ICU.
          // String language3 = getISO3Code(lang, LocaleISOData.isoLanguageTable);
          // if (language3 == null) {
          String language3 = ICU.getISO3Language(lang);
          if (!lang.isEmpty() && language3.isEmpty()) {
          // END Android-changed: Use ICU.
              throw new MissingResourceException("Couldn't find 3-letter language code for "
                      + lang, "FormatData_" + toString(), "ShortLanguage");
          }
          return language3;
      }
  
      /**
       * Returns a three-letter abbreviation for this locale's country.
       * If the country matches an ISO 3166-1 alpha-2 code, the
       * corresponding ISO 3166-1 alpha-3 uppercase code is returned.
       * If the locale doesn't specify a country, this will be the empty
       * string.
       *
       * <p>The ISO 3166-1 codes can be found on-line.
       *
       * @return A three-letter abbreviation of this locale's country.
       * @exception MissingResourceException Throws MissingResourceException if the
       * three-letter country abbreviation is not available for this locale.
       */
      public String getISO3Country() throws MissingResourceException {
          // BEGIN Android-changed: Use ICU. Also, use "" as ISO3 for missing regions.
          // String country3 = getISO3Code(baseLocale.getRegion(), LocaleISOData.isoCountryTable);
          // if (country3 == null) {
          final String region = baseLocale.getRegion();
          // Note that this will return an UN.M49 region code
          if (region.length() == 3) {
              return baseLocale.getRegion();
          } else if (region.isEmpty()) {
              return "";
          }
  
          // Prefix "en-" because ICU doesn't really care about what the language is.
          String country3 = ICU.getISO3Country("en-" + region);
          if (!region.isEmpty() && country3.isEmpty()) {
          // END Android-changed: Use ICU. Also, use "" as ISO3 for missing regions.
              throw new MissingResourceException("Couldn't find 3-letter country code for "
                      + baseLocale.getRegion(), "FormatData_" + toString(), "ShortCountry");
          }
          return country3;
      }
  
      // Android-removed: Use ICU.
      // getISO3Code() is unused on Android.
      /*
      private static String getISO3Code(String iso2Code, String table) {
          int codeLength = iso2Code.length();
          if (codeLength == 0) {
              return "";
          }
  
          int tableLength = table.length();
          int index = tableLength;
          if (codeLength == 2) {
              char c1 = iso2Code.charAt(0);
              char c2 = iso2Code.charAt(1);
              for (index = 0; index < tableLength; index += 5) {
                  if (table.charAt(index) == c1
                      && table.charAt(index + 1) == c2) {
                      break;
                  }
              }
          }
          return index < tableLength ? table.substring(index + 2, index + 5) : null;
      }
      */
  
      /**
       * Returns a name for the locale's language that is appropriate for display to the
       * user.
       * If possible, the name returned will be localized for the default
       * {@link Category#DISPLAY DISPLAY} locale.
       * For example, if the locale is fr_FR and the default
       * {@link Category#DISPLAY DISPLAY} locale
       * is en_US, getDisplayLanguage() will return "French"; if the locale is en_US and
       * the default {@link Category#DISPLAY DISPLAY} locale is fr_FR,
       * getDisplayLanguage() will return "anglais".
       * If the name returned cannot be localized for the default
       * {@link Category#DISPLAY DISPLAY} locale,
       * (say, we don't have a Japanese name for Croatian),
       * this function falls back on the English name, and uses the ISO code as a last-resort
       * value.  If the locale doesn't specify a language, this function returns the empty string.
       *
       * @return The name of the display language.
       */
      public final String getDisplayLanguage() {
          return getDisplayLanguage(getDefault(Category.DISPLAY));
      }
  
      // BEGIN Android-changed: Documentation and behavior of getDisplay*().
      // Use ICU; documentation; backwards compatibility hacks; added private helper methods.
      /*
      /**
       * Returns a name for the locale's language that is appropriate for display to the
       * user.
       * If possible, the name returned will be localized according to inLocale.
       * For example, if the locale is fr_FR and inLocale
       * is en_US, getDisplayLanguage() will return "French"; if the locale is en_US and
       * inLocale is fr_FR, getDisplayLanguage() will return "anglais".
       * If the name returned cannot be localized according to inLocale,
       * (say, we don't have a Japanese name for Croatian),
       * this function falls back on the English name, and finally
       * on the ISO code as a last-resort value.  If the locale doesn't specify a language,
       * this function returns the empty string.
       *
       * @param inLocale The locale for which to retrieve the display language.
       * @return The name of the display language appropriate to the given locale.
       * @exception NullPointerException if <code>inLocale</code> is <code>null</code>
       *
      public String getDisplayLanguage(Locale inLocale) {
          return getDisplayString(baseLocale.getLanguage(), inLocale, DISPLAY_LANGUAGE);
      }
      */
      /**
       * Returns the name of this locale's language, localized to {@code locale}.
       * If the language name is unknown, the language code is returned.
       */
      public String getDisplayLanguage(Locale locale) {
          String languageCode = baseLocale.getLanguage();
          if (languageCode.isEmpty()) {
              return "";
          }
  
          // Hacks for backward compatibility.
          //
          // Our language tag will contain "und" if the languageCode is invalid
          // or missing. ICU will then return "langue indéterminée" or the equivalent
          // display language for the indeterminate language code.
          //
          // Sigh... ugh... and what not.
          final String normalizedLanguage = normalizeAndValidateLanguage(
                  languageCode, false /* strict */);
          if (UNDETERMINED_LANGUAGE.equals(normalizedLanguage)) {
              return languageCode;
          }
  
          // TODO: We need a new hack or a complete fix for http://b/8049507 --- We would
          // cover the frameworks' tracks when they were using "tl" instead of "fil".
          String result = LocaleNative.getDisplayLanguage(this, locale);
          if (result == null) { // TODO: do we need to do this, or does ICU do it for us?
              result = LocaleNative.getDisplayLanguage(this, Locale.getDefault());
          }
          return result;
      }
  
      private static String normalizeAndValidateLanguage(String language, boolean strict) {
          if (language == null || language.isEmpty()) {
              return "";
          }
  
          final String lowercaseLanguage = language.toLowerCase(Locale.ROOT);
          if (!isValidBcp47Alpha(lowercaseLanguage, 2, 3)) {
              if (strict) {
                  throw new IllformedLocaleException("Invalid language: " + language);
              } else {
                  return UNDETERMINED_LANGUAGE;
              }
          }
  
          return lowercaseLanguage;
      }
  
      /*
       * Checks whether a given string is an ASCII alphanumeric string.
       */
      private static boolean isAsciiAlphaNum(String string) {
          for (int i = 0; i < string.length(); i++) {
              final char character = string.charAt(i);
              if (!(character >= 'a' && character <= 'z' ||
                      character >= 'A' && character <= 'Z' ||
                      character >= '0' && character <= '9')) {
                  return false;
              }
          }
  
          return true;
      }
      // END Android-changed: Documentation and behavior of getDisplay*().
  
      /**
       * Returns a name for the the locale's script that is appropriate for display to
       * the user. If possible, the name will be localized for the default
       * {@link Category#DISPLAY DISPLAY} locale.  Returns
       * the empty string if this locale doesn't specify a script code.
       *
       * @return the display name of the script code for the current default
       *     {@link Category#DISPLAY DISPLAY} locale
       * @since 1.7
       */
      public String getDisplayScript() {
          return getDisplayScript(getDefault(Category.DISPLAY));
      }
  
      /**
       * Returns a name for the locale's script that is appropriate
       * for display to the user. If possible, the name will be
       * localized for the given locale. Returns the empty string if
       * this locale doesn't specify a script code.
       *
       * @param inLocale The locale for which to retrieve the display script.
       * @return the display name of the script code for the current default
       * {@link Category#DISPLAY DISPLAY} locale
       * @throws NullPointerException if <code>inLocale</code> is <code>null</code>
       * @since 1.7
       */
      public String getDisplayScript(Locale inLocale) {
          // BEGIN Android-changed: Use ICU.
          // return getDisplayString(baseLocale.getScript(), inLocale, DISPLAY_SCRIPT);
          String scriptCode = baseLocale.getScript();
          if (scriptCode.isEmpty()) {
              return "";
          }
  
          String result = LocaleNative.getDisplayScript(this, inLocale);
          if (result == null) { // TODO: do we need to do this, or does ICU do it for us?
              result = LocaleNative.getDisplayScript(this, Locale.getDefault(Category.DISPLAY));
          }
  
          return result;
          // END Android-changed: Use ICU.
      }
  
      /**
       * Returns a name for the locale's country that is appropriate for display to the
       * user.
       * If possible, the name returned will be localized for the default
       * {@link Category#DISPLAY DISPLAY} locale.
       * For example, if the locale is fr_FR and the default
       * {@link Category#DISPLAY DISPLAY} locale
       * is en_US, getDisplayCountry() will return "France"; if the locale is en_US and
       * the default {@link Category#DISPLAY DISPLAY} locale is fr_FR,
       * getDisplayCountry() will return "Etats-Unis".
       * If the name returned cannot be localized for the default
       * {@link Category#DISPLAY DISPLAY} locale,
       * (say, we don't have a Japanese name for Croatia),
       * this function falls back on the English name, and uses the ISO code as a last-resort
       * value.  If the locale doesn't specify a country, this function returns the empty string.
       *
       * @return The name of the country appropriate to the locale.
       */
      public final String getDisplayCountry() {
          return getDisplayCountry(getDefault(Category.DISPLAY));
      }
  
      // BEGIN Android-changed: Documentation and behavior of getDisplay*().
      // Use ICU; documentation; added private helper methods.
      /*
      /**
       * Returns a name for the locale's country that is appropriate for display to the
       * user.
       * If possible, the name returned will be localized according to inLocale.
       * For example, if the locale is fr_FR and inLocale
       * is en_US, getDisplayCountry() will return "France"; if the locale is en_US and
       * inLocale is fr_FR, getDisplayCountry() will return "Etats-Unis".
       * If the name returned cannot be localized according to inLocale.
       * (say, we don't have a Japanese name for Croatia),
       * this function falls back on the English name, and finally
       * on the ISO code as a last-resort value.  If the locale doesn't specify a country,
       * this function returns the empty string.
       *
       * @param inLocale The locale for which to retrieve the display country.
       * @return The name of the country appropriate to the given locale.
       * @exception NullPointerException if <code>inLocale</code> is <code>null</code>
       *
      public String getDisplayCountry(Locale inLocale) {
          return getDisplayString(baseLocale.getRegion(), inLocale, DISPLAY_COUNTRY);
      }
  
      private String getDisplayString(String code, Locale inLocale, int type) {
          if (code.length() == 0) {
              return "";
          }
  
          if (inLocale == null) {
              throw new NullPointerException();
          }
  
          LocaleServiceProviderPool pool =
              LocaleServiceProviderPool.getPool(LocaleNameProvider.class);
          String key = (type == DISPLAY_VARIANT ? "%%"+code : code);
          String result = pool.getLocalizedObject(
                                  LocaleNameGetter.INSTANCE,
                                  inLocale, key, type, code);
              if (result != null) {
                  return result;
              }
  
          return code;
      }
      */
      /**
       * Returns the name of this locale's country, localized to {@code locale}.
       * Returns the empty string if this locale does not correspond to a specific
       * country.
       */
      public String getDisplayCountry(Locale locale) {
          String countryCode = baseLocale.getRegion();
          if (countryCode.isEmpty()) {
              return "";
          }
  
          final String normalizedRegion = normalizeAndValidateRegion(
                  countryCode, false /* strict */);
          if (normalizedRegion.isEmpty()) {
              return countryCode;
          }
  
          String result = LocaleNative.getDisplayCountry(this, locale);
          if (result == null) { // TODO: do we need to do this, or does ICU do it for us?
              result = LocaleNative.getDisplayCountry(this, Locale.getDefault());
          }
          return result;
      }
  
      private static String normalizeAndValidateRegion(String region, boolean strict) {
          if (region == null || region.isEmpty()) {
              return "";
          }
  
          final String uppercaseRegion = region.toUpperCase(Locale.ROOT);
          if (!isValidBcp47Alpha(uppercaseRegion, 2, 2) &&
                  !isUnM49AreaCode(uppercaseRegion)) {
              if (strict) {
                  throw new IllformedLocaleException("Invalid region: " + region);
              } else {
                  return "";
              }
          }
  
          return uppercaseRegion;
      }
  
      private static boolean isValidBcp47Alpha(String string, int lowerBound, int upperBound) {
          final int length = string.length();
          if (length < lowerBound || length > upperBound) {
              return false;
          }
  
          for (int i = 0; i < length; ++i) {
              final char character = string.charAt(i);
              if (!(character >= 'a' && character <= 'z' ||
                      character >= 'A' && character <= 'Z')) {
                  return false;
              }
          }
  
          return true;
      }
  
      /**
       * A UN M.49 is a 3 digit numeric code.
       */
      private static boolean isUnM49AreaCode(String code) {
          if (code.length() != 3) {
              return false;
          }
  
          for (int i = 0; i < 3; ++i) {
              final char character = code.charAt(i);
              if (!(character >= '0' && character <= '9')) {
                  return false;
              }
          }
  
          return true;
      }
      // END Android-changed: Documentation and behavior of getDisplay*().
  
      /**
       * Returns a name for the locale's variant code that is appropriate for display to the
       * user.  If possible, the name will be localized for the default
       * {@link Category#DISPLAY DISPLAY} locale.  If the locale
       * doesn't specify a variant code, this function returns the empty string.
       *
       * @return The name of the display variant code appropriate to the locale.
       */
      public final String getDisplayVariant() {
          return getDisplayVariant(getDefault(Category.DISPLAY));
      }
  
      /**
       * Returns a name for the locale's variant code that is appropriate for display to the
       * user.  If possible, the name will be localized for inLocale.  If the locale
       * doesn't specify a variant code, this function returns the empty string.
       *
       * @param inLocale The locale for which to retrieve the display variant code.
       * @return The name of the display variant code appropriate to the given locale.
       * @exception NullPointerException if <code>inLocale</code> is <code>null</code>
       */
      public String getDisplayVariant(Locale inLocale) {
  // BEGIN Android-changed: Documentation and behavior of getDisplay*().
  // Use ICU; added private helper methods.
  /*
          if (baseLocale.getVariant().length() == 0)
              return "";
  
          LocaleResources lr = LocaleProviderAdapter.forJRE().getLocaleResources(inLocale);
  
          String names[] = getDisplayVariantArray(inLocale);
  
          // Get the localized patterns for formatting a list, and use
          // them to format the list.
          return formatList(names,
                            lr.getLocaleName("ListPattern"),
                            lr.getLocaleName("ListCompositionPattern"));
      }
  */
          String variantCode = baseLocale.getVariant();
          if (variantCode.isEmpty()) {
              return "";
          }
  
          try {
              normalizeAndValidateVariant(variantCode);
          } catch (IllformedLocaleException ilfe) {
              return variantCode;
          }
  
          String result = LocaleNative.getDisplayVariant(this, inLocale);
          if (result == null) { // TODO: do we need to do this, or does ICU do it for us?
              result = LocaleNative.getDisplayVariant(this, Locale.getDefault());
          }
  
          // The "old style" locale constructors allow us to pass in variants that aren't
          // valid BCP-47 variant subtags. When that happens, toLanguageTag will not emit
          // them. Note that we know variantCode.length() > 0 due to the isEmpty check at
          // the beginning of this function.
          if (result.isEmpty()) {
              return variantCode;
          }
          return result;
      }
  
      private static String normalizeAndValidateVariant(String variant) {
          if (variant == null || variant.isEmpty()) {
              return "";
          }
  
          // Note that unlike extensions, we canonicalize to lower case alphabets
          // and underscores instead of hyphens.
          final String normalizedVariant = variant.replace('-', '_');
          String[] subTags = normalizedVariant.split("_");
  
          for (String subTag : subTags) {
              if (!isValidVariantSubtag(subTag)) {
                  throw new IllformedLocaleException("Invalid variant: " + variant);
              }
          }
  
          return normalizedVariant;
      }
  
      private static boolean isValidVariantSubtag(String subTag) {
          // The BCP-47 spec states that :
          // - Subtags can be between [5, 8] alphanumeric chars in length.
          // - Subtags that start with a number are allowed to be 4 chars in length.
          if (subTag.length() >= 5 && subTag.length() <= 8) {
              if (isAsciiAlphaNum(subTag)) {
                  return true;
              }
          } else if (subTag.length() == 4) {
              final char firstChar = subTag.charAt(0);
              if ((firstChar >= '0' && firstChar <= '9') && isAsciiAlphaNum(subTag)) {
                  return true;
              }
          }
  
          return false;
      }
  // END Android-changed: Documentation and behavior of getDisplay*().
  
      /**
       * Returns a name for the locale that is appropriate for display to the
       * user. This will be the values returned by getDisplayLanguage(),
       * getDisplayScript(), getDisplayCountry(), and getDisplayVariant() assembled
       * into a single string. The the non-empty values are used in order,
       * with the second and subsequent names in parentheses.  For example:
       * <blockquote>
       * language (script, country, variant)<br>
       * language (country)<br>
       * language (variant)<br>
       * script (country)<br>
       * country<br>
       * </blockquote>
       * depending on which fields are specified in the locale.  If the
       * language, script, country, and variant fields are all empty,
       * this function returns the empty string.
       *
       * @return The name of the locale appropriate to display.
       */
      public final String getDisplayName() {
          return getDisplayName(getDefault(Category.DISPLAY));
      }
  
      // BEGIN Android-changed: Documentation and behavior of getDisplay*().
      /*
      /**
       * Returns a name for the locale that is appropriate for display
       * to the user.  This will be the values returned by
       * getDisplayLanguage(), getDisplayScript(),getDisplayCountry(),
       * and getDisplayVariant() assembled into a single string.
       * The non-empty values are used in order,
       * with the second and subsequent names in parentheses.  For example:
       * <blockquote>
       * language (script, country, variant)<br>
       * language (country)<br>
       * language (variant)<br>
       * script (country)<br>
       * country<br>
       * </blockquote>
       * depending on which fields are specified in the locale.  If the
       * language, script, country, and variant fields are all empty,
       * this function returns the empty string.
       *
       * @param inLocale The locale for which to retrieve the display name.
       * @return The name of the locale appropriate to display.
       * @throws NullPointerException if <code>inLocale</code> is <code>null</code>
       *
      public String getDisplayName(Locale inLocale) {
          LocaleResources lr =  LocaleProviderAdapter.forJRE().getLocaleResources(inLocale);
  
          String languageName = getDisplayLanguage(inLocale);
          String scriptName = getDisplayScript(inLocale);
          String countryName = getDisplayCountry(inLocale);
          String[] variantNames = getDisplayVariantArray(inLocale);
  
          // Get the localized patterns for formatting a display name.
          String displayNamePattern = lr.getLocaleName("DisplayNamePattern");
          String listPattern = lr.getLocaleName("ListPattern");
          String listCompositionPattern = lr.getLocaleName("ListCompositionPattern");
  
          // The display name consists of a main name, followed by qualifiers.
          // Typically, the format is "MainName (Qualifier, Qualifier)" but this
          // depends on what pattern is stored in the display locale.
          String   mainName       = null;
          String[] qualifierNames = null;
  
          // The main name is the language, or if there is no language, the script,
          // then if no script, the country. If there is no language/script/country
          // (an anomalous situation) then the display name is simply the variant's
          // display name.
          if (languageName.length() == 0 && scriptName.length() == 0 && countryName.length() == 0) {
              if (variantNames.length == 0) {
                  return "";
              } else {
                  return formatList(variantNames, listPattern, listCompositionPattern);
              }
          }
          ArrayList<String> names = new ArrayList<>(4);
          if (languageName.length() != 0) {
              names.add(languageName);
          }
          if (scriptName.length() != 0) {
              names.add(scriptName);
          }
          if (countryName.length() != 0) {
              names.add(countryName);
          }
          if (variantNames.length != 0) {
              names.addAll(Arrays.asList(variantNames));
          }
  
          // The first one in the main name
          mainName = names.get(0);
  
          // Others are qualifiers
          int numNames = names.size();
          qualifierNames = (numNames > 1) ?
                  names.subList(1, numNames).toArray(new String[numNames - 1]) : new String[0];
  
          // Create an array whose first element is the number of remaining
          // elements.  This serves as a selector into a ChoiceFormat pattern from
          // the resource.  The second and third elements are the main name and
          // the qualifier; if there are no qualifiers, the third element is
          // unused by the format pattern.
          Object[] displayNames = {
              new Integer(qualifierNames.length != 0 ? 2 : 1),
              mainName,
              // We could also just call formatList() and have it handle the empty
              // list case, but this is more efficient, and we want it to be
              // efficient since all the language-only locales will not have any
              // qualifiers.
              qualifierNames.length != 0 ? formatList(qualifierNames, listPattern, listCompositionPattern) : null
          };
  
          if (displayNamePattern != null) {
              return new MessageFormat(displayNamePattern).format(displayNames);
          }
          else {
              // If we cannot get the message format pattern, then we use a simple
              // hard-coded pattern.  This should not occur in practice unless the
              // installation is missing some core files (FormatData etc.).
              StringBuilder result = new StringBuilder();
              result.append((String)displayNames[1]);
              if (displayNames.length > 2) {
                  result.append(" (");
                  result.append((String)displayNames[2]);
                  result.append(')');
              }
              return result.toString();
          }
      }
      */
      /**
       * Returns this locale's language name, country name, and variant, localized
       * to {@code locale}. The exact output form depends on whether this locale
       * corresponds to a specific language, script, country and variant.
       *
       * <p>For example:
       * <ul>
       * <li>{@code new Locale("en").getDisplayName(Locale.US)} -> {@code English}
       * <li>{@code new Locale("en", "US").getDisplayName(Locale.US)} -> {@code English (United States)}
       * <li>{@code new Locale("en", "US", "POSIX").getDisplayName(Locale.US)} -> {@code English (United States,Computer)}
       * <li>{@code Locale.forLanguageTag("zh-Hant-CN").getDisplayName(Locale.US)} -> {@code Chinese (Traditional Han,China)}
       * <li>{@code new Locale("en").getDisplayName(Locale.FRANCE)} -> {@code anglais}
       * <li>{@code new Locale("en", "US").getDisplayName(Locale.FRANCE)} -> {@code anglais (États-Unis)}
       * <li>{@code new Locale("en", "US", "POSIX").getDisplayName(Locale.FRANCE)} -> {@code anglais (États-Unis,informatique)}.
       * </ul>
       */
      public String getDisplayName(Locale locale) {
          int count = 0;
          StringBuilder buffer = new StringBuilder();
          String languageCode = baseLocale.getLanguage();
          if (!languageCode.isEmpty()) {
              String displayLanguage = getDisplayLanguage(locale);
              buffer.append(displayLanguage.isEmpty() ? languageCode : displayLanguage);
              ++count;
          }
          String scriptCode = baseLocale.getScript();
          if (!scriptCode.isEmpty()) {
              if (count == 1) {
                  buffer.append(" (");
              }
              String displayScript = getDisplayScript(locale);
              buffer.append(displayScript.isEmpty() ? scriptCode : displayScript);
              ++count;
          }
          String countryCode = baseLocale.getRegion();
          if (!countryCode.isEmpty()) {
              if (count == 1) {
                  buffer.append(" (");
              } else if (count == 2) {
                  buffer.append(",");
              }
              String displayCountry = getDisplayCountry(locale);
              buffer.append(displayCountry.isEmpty() ? countryCode : displayCountry);
              ++count;
          }
          String variantCode = baseLocale.getVariant();
          if (!variantCode.isEmpty()) {
              if (count == 1) {
                  buffer.append(" (");
              } else if (count == 2 || count == 3) {
                  buffer.append(",");
              }
              String displayVariant = getDisplayVariant(locale);
              buffer.append(displayVariant.isEmpty() ? variantCode : displayVariant);
              ++count;
          }
          if (count > 1) {
              buffer.append(")");
          }
          return buffer.toString();
      }
      // END Android-changed: Documentation and behavior of getDisplay*().
  
      /**
       * Overrides Cloneable.
       */
      @Override
      public Object clone()
      {
          try {
              Locale that = (Locale)super.clone();
              return that;
          } catch (CloneNotSupportedException e) {
              throw new InternalError(e);
          }
      }
  
      /**
       * Override hashCode.
       * Since Locales are often used in hashtables, caches the value
       * for speed.
       */
      @Override
      public int hashCode() {
          int hc = hashCodeValue;
          if (hc == 0) {
              hc = baseLocale.hashCode();
              if (localeExtensions != null) {
                  hc ^= localeExtensions.hashCode();
              }
              hashCodeValue = hc;
          }
          return hc;
      }
  
      // Overrides
  
      /**
       * Returns true if this Locale is equal to another object.  A Locale is
       * deemed equal to another Locale with identical language, script, country,
       * variant and extensions, and unequal to all other objects.
       *
       * @return true if this Locale is equal to the specified object.
       */
      @Override
      public boolean equals(Object obj) {
          if (this == obj)                      // quick check
              return true;
          if (!(obj instanceof Locale))
              return false;
          BaseLocale otherBase = ((Locale)obj).baseLocale;
          if (!baseLocale.equals(otherBase)) {
              return false;
          }
          if (localeExtensions == null) {
              return ((Locale)obj).localeExtensions == null;
          }
          return localeExtensions.equals(((Locale)obj).localeExtensions);
      }
  
      // ================= privates =====================================
  
      private transient BaseLocale baseLocale;
      private transient LocaleExtensions localeExtensions;
  
      /**
       * Calculated hashcode
       */
      private transient volatile int hashCodeValue = 0;
  
      // Android-changed: Add NoImagePreloadHolder to allow compile-time initialization.
      // private volatile static Locale defaultLocale = initDefault();
      private static class NoImagePreloadHolder {
          public volatile static Locale defaultLocale = initDefault();
      }
      private volatile static Locale defaultDisplayLocale = null;
      private volatile static Locale defaultFormatLocale = null;
  
      private transient volatile String languageTag;
  
      // BEGIN Android-removed: Private helper getDisplayVariantArray() unused on Android.
      /*
      /**
       * Return an array of the display names of the variant.
       * @param bundle the ResourceBundle to use to get the display names
       * @return an array of display names, possible of zero length.
       *
      private String[] getDisplayVariantArray(Locale inLocale) {
          // Split the variant name into tokens separated by '_'.
          StringTokenizer tokenizer = new StringTokenizer(baseLocale.getVariant(), "_");
          String[] names = new String[tokenizer.countTokens()];
  
          // For each variant token, lookup the display name.  If
          // not found, use the variant name itself.
          for (int i=0; i<names.length; ++i) {
              names[i] = getDisplayString(tokenizer.nextToken(),
                                  inLocale, DISPLAY_VARIANT);
          }
  
          return names;
      }
      */
      // END Android-removed: Private helper getDisplayVariantArray() unused on Android.
  
      /**
       * Format a list using given pattern strings.
       * If either of the patterns is null, then a the list is
       * formatted by concatenation with the delimiter ','.
       * @param stringList the list of strings to be formatted.
       * @param listPattern should create a MessageFormat taking 0-3 arguments
       * and formatting them into a list.
       * @param listCompositionPattern should take 2 arguments
       * and is used by composeList.
       * @return a string representing the list.
       */
      private static String formatList(String[] stringList, String listPattern, String listCompositionPattern) {
          // If we have no list patterns, compose the list in a simple,
          // non-localized way.
          if (listPattern == null || listCompositionPattern == null) {
              StringBuilder result = new StringBuilder();
              for (int i = 0; i < stringList.length; ++i) {
                  if (i > 0) {
                      result.append(',');
                  }
                  result.append(stringList[i]);
              }
              return result.toString();
          }
  
          // Compose the list down to three elements if necessary
          if (stringList.length > 3) {
              MessageFormat format = new MessageFormat(listCompositionPattern);
              stringList = composeList(format, stringList);
          }
  
          // Rebuild the argument list with the list length as the first element
          Object[] args = new Object[stringList.length + 1];
          System.arraycopy(stringList, 0, args, 1, stringList.length);
          args[0] = new Integer(stringList.length);
  
          // Format it using the pattern in the resource
          MessageFormat format = new MessageFormat(listPattern);
          return format.format(args);
      }
  
      /**
       * Given a list of strings, return a list shortened to three elements.
       * Shorten it by applying the given format to the first two elements
       * recursively.
       * @param format a format which takes two arguments
       * @param list a list of strings
       * @return if the list is three elements or shorter, the same list;
       * otherwise, a new list of three elements.
       */
      private static String[] composeList(MessageFormat format, String[] list) {
          if (list.length <= 3) return list;
  
          // Use the given format to compose the first two elements into one
          String[] listItems = { list[0], list[1] };
          String newItem = format.format(listItems);
  
          // Form a new list one element shorter
          String[] newList = new String[list.length-1];
          System.arraycopy(list, 2, newList, 1, newList.length-1);
          newList[0] = newItem;
  
          // Recurse
          return composeList(format, newList);
      }
  
      // Duplicate of sun.util.locale.UnicodeLocaleExtension.isKey in order to
      // avoid its class loading.
      private static boolean isUnicodeExtensionKey(String s) {
          // 2alphanum
          return (s.length() == 2) && LocaleUtils.isAlphaNumericString(s);
      }
  
      /**
       * @serialField language    String
       *      language subtag in lower case. (See <a href="java/util/Locale.html#getLanguage()">getLanguage()</a>)
       * @serialField country     String
       *      country subtag in upper case. (See <a href="java/util/Locale.html#getCountry()">getCountry()</a>)
       * @serialField variant     String
       *      variant subtags separated by LOWLINE characters. (See <a href="java/util/Locale.html#getVariant()">getVariant()</a>)
       * @serialField hashcode    int
       *      deprecated, for forward compatibility only
       * @serialField script      String
       *      script subtag in title case (See <a href="java/util/Locale.html#getScript()">getScript()</a>)
       * @serialField extensions  String
       *      canonical representation of extensions, that is,
       *      BCP47 extensions in alphabetical order followed by
       *      BCP47 private use subtags, all in lower case letters
       *      separated by HYPHEN-MINUS characters.
       *      (See <a href="java/util/Locale.html#getExtensionKeys()">getExtensionKeys()</a>,
       *      <a href="java/util/Locale.html#getExtension(char)">getExtension(char)</a>)
       */
      private static final ObjectStreamField[] serialPersistentFields = {
          new ObjectStreamField("language", String.class),
          new ObjectStreamField("country", String.class),
          new ObjectStreamField("variant", String.class),
          new ObjectStreamField("hashcode", int.class),
          new ObjectStreamField("script", String.class),
          new ObjectStreamField("extensions", String.class),
      };
  
      /**
       * Serializes this <code>Locale</code> to the specified <code>ObjectOutputStream</code>.
       * @param out the <code>ObjectOutputStream</code> to write
       * @throws IOException
       * @since 1.7
       */
      private void writeObject(ObjectOutputStream out) throws IOException {
          ObjectOutputStream.PutField fields = out.putFields();
          fields.put("language", baseLocale.getLanguage());
          fields.put("script", baseLocale.getScript());
          fields.put("country", baseLocale.getRegion());
          fields.put("variant", baseLocale.getVariant());
          fields.put("extensions", localeExtensions == null ? "" : localeExtensions.getID());
          fields.put("hashcode", -1); // place holder just for backward support
          out.writeFields();
      }
  
      /**
       * Deserializes this <code>Locale</code>.
       * @param in the <code>ObjectInputStream</code> to read
       * @throws IOException
       * @throws ClassNotFoundException
       * @throws IllformedLocaleException
       * @since 1.7
       */
      private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
          ObjectInputStream.GetField fields = in.readFields();
          String language = (String)fields.get("language", "");
          String script = (String)fields.get("script", "");
          String country = (String)fields.get("country", "");
          String variant = (String)fields.get("variant", "");
          String extStr = (String)fields.get("extensions", "");
          baseLocale = BaseLocale.getInstance(convertOldISOCodes(language), script, country, variant);
          // Android-changed: Handle null for backwards compatible deserialization. http://b/26387905
          // if (extStr.length() > 0) {
          if (extStr != null && extStr.length() > 0) {
              try {
                  InternalLocaleBuilder bldr = new InternalLocaleBuilder();
                  bldr.setExtensions(extStr);
                  localeExtensions = bldr.getLocaleExtensions();
              } catch (LocaleSyntaxException e) {
                  throw new IllformedLocaleException(e.getMessage());
              }
          } else {
              localeExtensions = null;
          }
      }
  
      /**
       * Returns a cached <code>Locale</code> instance equivalent to
       * the deserialized <code>Locale</code>. When serialized
       * language, country and variant fields read from the object data stream
       * are exactly "ja", "JP", "JP" or "th", "TH", "TH" and script/extensions
       * fields are empty, this method supplies <code>UNICODE_LOCALE_EXTENSION</code>
       * "ca"/"japanese" (calendar type is "japanese") or "nu"/"thai" (number script
       * type is "thai"). See <a href="Locale.html#special_cases_constructor">Special Cases</a>
       * for more information.
       *
       * @return an instance of <code>Locale</code> equivalent to
       * the deserialized <code>Locale</code>.
       * @throws java.io.ObjectStreamException
       */
      private Object readResolve() throws java.io.ObjectStreamException {
          return getInstance(baseLocale.getLanguage(), baseLocale.getScript(),
                  baseLocale.getRegion(), baseLocale.getVariant(), localeExtensions);
      }
  
      private static volatile String[] isoLanguages = null;
  
      private static volatile String[] isoCountries = null;
  
      private static String convertOldISOCodes(String language) {
          // we accept both the old and the new ISO codes for the languages whose ISO
          // codes have changed, but we always store the OLD code, for backward compatibility
          language = LocaleUtils.toLowerString(language).intern();
          if (language == "he") {
              return "iw";
          } else if (language == "yi") {
              return "ji";
          } else if (language == "id") {
              return "in";
          } else {
              return language;
          }
      }
  
      private static LocaleExtensions getCompatibilityExtensions(String language,
                                                                 String script,
                                                                 String country,
                                                                 String variant) {
          LocaleExtensions extensions = null;
          // Special cases for backward compatibility support
          if (LocaleUtils.caseIgnoreMatch(language, "ja")
                  && script.length() == 0
                  && LocaleUtils.caseIgnoreMatch(country, "jp")
                  && "JP".equals(variant)) {
              // ja_JP_JP -> u-ca-japanese (calendar = japanese)
              extensions = LocaleExtensions.CALENDAR_JAPANESE;
          } else if (LocaleUtils.caseIgnoreMatch(language, "th")
                  && script.length() == 0
                  && LocaleUtils.caseIgnoreMatch(country, "th")
                  && "TH".equals(variant)) {
              // th_TH_TH -> u-nu-thai (numbersystem = thai)
              extensions = LocaleExtensions.NUMBER_THAI;
          }
          return extensions;
      }
  
      // Android-removed: Drop nested private class LocaleNameGetter.
      /*
      /**
       * Obtains a localized locale names from a LocaleNameProvider
       * implementation.
       *
      private static class LocaleNameGetter
          implements LocaleServiceProviderPool.LocalizedObjectGetter<LocaleNameProvider, String> {
          private static final LocaleNameGetter INSTANCE = new LocaleNameGetter();
  
          @Override
          public String getObject(LocaleNameProvider localeNameProvider,
                                  Locale locale,
                                  String key,
                                  Object... params) {
              assert params.length == 2;
              int type = (Integer)params[0];
              String code = (String)params[1];
  
              switch(type) {
              case DISPLAY_LANGUAGE:
                  return localeNameProvider.getDisplayLanguage(code, locale);
              case DISPLAY_COUNTRY:
                  return localeNameProvider.getDisplayCountry(code, locale);
              case DISPLAY_VARIANT:
                  return localeNameProvider.getDisplayVariant(code, locale);
              case DISPLAY_SCRIPT:
                  return localeNameProvider.getDisplayScript(code, locale);
              default:
                  assert false; // shouldn't happen
              }
  
              return null;
          }
      }
      */
  
      // BEGIN Android-added: adjustLanguageCode(), for internal use only.
      /** @hide for internal use only. */
      public static String adjustLanguageCode(String languageCode) {
          String adjusted = languageCode.toLowerCase(Locale.US);
          // Map new language codes to the obsolete language
          // codes so the correct resource bundles will be used.
          if (languageCode.equals("he")) {
              adjusted = "iw";
          } else if (languageCode.equals("id")) {
              adjusted = "in";
          } else if (languageCode.equals("yi")) {
              adjusted = "ji";
          }
  
          return adjusted;
      }
      // END Android-added: adjustLanguageCode(), for internal use only.
  
      /**
       * Enum for locale categories.  These locale categories are used to get/set
       * the default locale for the specific functionality represented by the
       * category.
       *
       * @see #getDefault(Category)
       * @see #setDefault(Category, Locale)
       * @since 1.7
       */
      public enum Category {
  
          /**
           * Category used to represent the default locale for
           * displaying user interfaces.
           */
          DISPLAY("user.language.display",
                  "user.script.display",
                  "user.country.display",
                  "user.variant.display"),
  
          /**
           * Category used to represent the default locale for
           * formatting dates, numbers, and/or currencies.
           */
          FORMAT("user.language.format",
                 "user.script.format",
                 "user.country.format",
                 "user.variant.format");
  
          Category(String languageKey, String scriptKey, String countryKey, String variantKey) {
              this.languageKey = languageKey;
              this.scriptKey = scriptKey;
              this.countryKey = countryKey;
              this.variantKey = variantKey;
          }
  
          final String languageKey;
          final String scriptKey;
          final String countryKey;
          final String variantKey;
      }
  
      /**
       * <code>Builder</code> is used to build instances of <code>Locale</code>
       * from values configured by the setters.  Unlike the <code>Locale</code>
       * constructors, the <code>Builder</code> checks if a value configured by a
       * setter satisfies the syntax requirements defined by the <code>Locale</code>
       * class.  A <code>Locale</code> object created by a <code>Builder</code> is
       * well-formed and can be transformed to a well-formed IETF BCP 47 language tag
       * without losing information.
       *
       * <p><b>Note:</b> The <code>Locale</code> class does not provide any
       * syntactic restrictions on variant, while BCP 47 requires each variant
       * subtag to be 5 to 8 alphanumerics or a single numeric followed by 3
       * alphanumerics.  The method <code>setVariant</code> throws
       * <code>IllformedLocaleException</code> for a variant that does not satisfy
       * this restriction. If it is necessary to support such a variant, use a
       * Locale constructor.  However, keep in mind that a <code>Locale</code>
       * object created this way might lose the variant information when
       * transformed to a BCP 47 language tag.
       *
       * <p>The following example shows how to create a <code>Locale</code> object
       * with the <code>Builder</code>.
       * <blockquote>
       * <pre>
       *     Locale aLocale = new Builder().setLanguage("sr").setScript("Latn").setRegion("RS").build();
       * </pre>
       * </blockquote>
       *
       * <p>Builders can be reused; <code>clear()</code> resets all
       * fields to their default values.
       *
       * @see Locale#forLanguageTag
       * @since 1.7
       */
      public static final class Builder {
          private final InternalLocaleBuilder localeBuilder;
  
          /**
           * Constructs an empty Builder. The default value of all
           * fields, extensions, and private use information is the
           * empty string.
           */
          public Builder() {
              localeBuilder = new InternalLocaleBuilder();
          }
  
          /**
           * Resets the <code>Builder</code> to match the provided
           * <code>locale</code>.  Existing state is discarded.
           *
           * <p>All fields of the locale must be well-formed, see {@link Locale}.
           *
           * <p>Locales with any ill-formed fields cause
           * <code>IllformedLocaleException</code> to be thrown, except for the
           * following three cases which are accepted for compatibility
           * reasons:<ul>
           * <li>Locale("ja", "JP", "JP") is treated as "ja-JP-u-ca-japanese"
           * <li>Locale("th", "TH", "TH") is treated as "th-TH-u-nu-thai"
           * <li>Locale("no", "NO", "NY") is treated as "nn-NO"</ul>
           *
           * @param locale the locale
           * @return This builder.
           * @throws IllformedLocaleException if <code>locale</code> has
           * any ill-formed fields.
           * @throws NullPointerException if <code>locale</code> is null.
           */
          public Builder setLocale(Locale locale) {
              try {
                  localeBuilder.setLocale(locale.baseLocale, locale.localeExtensions);
              } catch (LocaleSyntaxException e) {
                  throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
              }
              return this;
          }
  
          /**
           * Resets the Builder to match the provided IETF BCP 47
           * language tag.  Discards the existing state.  Null and the
           * empty string cause the builder to be reset, like {@link
           * #clear}.  Grandfathered tags (see {@link
           * Locale#forLanguageTag}) are converted to their canonical
           * form before being processed.  Otherwise, the language tag
           * must be well-formed (see {@link Locale}) or an exception is
           * thrown (unlike <code>Locale.forLanguageTag</code>, which
           * just discards ill-formed and following portions of the
           * tag).
           *
           * @param languageTag the language tag
           * @return This builder.
           * @throws IllformedLocaleException if <code>languageTag</code> is ill-formed
           * @see Locale#forLanguageTag(String)
           */
          public Builder setLanguageTag(String languageTag) {
              ParseStatus sts = new ParseStatus();
              LanguageTag tag = LanguageTag.parse(languageTag, sts);
              if (sts.isError()) {
                  throw new IllformedLocaleException(sts.getErrorMessage(), sts.getErrorIndex());
              }
              localeBuilder.setLanguageTag(tag);
              return this;
          }
  
          /**
           * Sets the language.  If <code>language</code> is the empty string or
           * null, the language in this <code>Builder</code> is removed.  Otherwise,
           * the language must be <a href="./Locale.html#def_language">well-formed</a>
           * or an exception is thrown.
           *
           * <p>The typical language value is a two or three-letter language
           * code as defined in ISO639.
           *
           * @param language the language
           * @return This builder.
           * @throws IllformedLocaleException if <code>language</code> is ill-formed
           */
          public Builder setLanguage(String language) {
              try {
                  localeBuilder.setLanguage(language);
              } catch (LocaleSyntaxException e) {
                  throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
              }
              return this;
          }
  
          /**
           * Sets the script. If <code>script</code> is null or the empty string,
           * the script in this <code>Builder</code> is removed.
           * Otherwise, the script must be <a href="./Locale.html#def_script">well-formed</a> or an
           * exception is thrown.
           *
           * <p>The typical script value is a four-letter script code as defined by ISO 15924.
           *
           * @param script the script
           * @return This builder.
           * @throws IllformedLocaleException if <code>script</code> is ill-formed
           */
          public Builder setScript(String script) {
              try {
                  localeBuilder.setScript(script);
              } catch (LocaleSyntaxException e) {
                  throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
              }
              return this;
          }
  
          /**
           * Sets the region.  If region is null or the empty string, the region
           * in this <code>Builder</code> is removed.  Otherwise,
           * the region must be <a href="./Locale.html#def_region">well-formed</a> or an
           * exception is thrown.
           *
           * <p>The typical region value is a two-letter ISO 3166 code or a
           * three-digit UN M.49 area code.
           *
           * <p>The country value in the <code>Locale</code> created by the
           * <code>Builder</code> is always normalized to upper case.
           *
           * @param region the region
           * @return This builder.
           * @throws IllformedLocaleException if <code>region</code> is ill-formed
           */
          public Builder setRegion(String region) {
              try {
                  localeBuilder.setRegion(region);
              } catch (LocaleSyntaxException e) {
                  throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
              }
              return this;
          }
  
          /**
           * Sets the variant.  If variant is null or the empty string, the
           * variant in this <code>Builder</code> is removed.  Otherwise, it
           * must consist of one or more <a href="./Locale.html#def_variant">well-formed</a>
           * subtags, or an exception is thrown.
           *
           * <p><b>Note:</b> This method checks if <code>variant</code>
           * satisfies the IETF BCP 47 variant subtag's syntax requirements,
           * and normalizes the value to lowercase letters.  However,
           * the <code>Locale</code> class does not impose any syntactic
           * restriction on variant, and the variant value in
           * <code>Locale</code> is case sensitive.  To set such a variant,
           * use a Locale constructor.
           *
           * @param variant the variant
           * @return This builder.
           * @throws IllformedLocaleException if <code>variant</code> is ill-formed
           */
          public Builder setVariant(String variant) {
              try {
                  localeBuilder.setVariant(variant);
              } catch (LocaleSyntaxException e) {
                  throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
              }
              return this;
          }
  
          /**
           * Sets the extension for the given key. If the value is null or the
           * empty string, the extension is removed.  Otherwise, the extension
           * must be <a href="./Locale.html#def_extensions">well-formed</a> or an exception
           * is thrown.
           *
           * <p><b>Note:</b> The key {@link Locale#UNICODE_LOCALE_EXTENSION
           * UNICODE_LOCALE_EXTENSION} ('u') is used for the Unicode locale extension.
           * Setting a value for this key replaces any existing Unicode locale key/type
           * pairs with those defined in the extension.
           *
           * <p><b>Note:</b> The key {@link Locale#PRIVATE_USE_EXTENSION
           * PRIVATE_USE_EXTENSION} ('x') is used for the private use code. To be
           * well-formed, the value for this key needs only to have subtags of one to
           * eight alphanumeric characters, not two to eight as in the general case.
           *
           * @param key the extension key
           * @param value the extension value
           * @return This builder.
           * @throws IllformedLocaleException if <code>key</code> is illegal
           * or <code>value</code> is ill-formed
           * @see #setUnicodeLocaleKeyword(String, String)
           */
          public Builder setExtension(char key, String value) {
              try {
                  localeBuilder.setExtension(key, value);
              } catch (LocaleSyntaxException e) {
                  throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
              }
              return this;
          }
  
          /**
           * Sets the Unicode locale keyword type for the given key.  If the type
           * is null, the Unicode keyword is removed.  Otherwise, the key must be
           * non-null and both key and type must be <a
           * href="./Locale.html#def_locale_extension">well-formed</a> or an exception
           * is thrown.
           *
           * <p>Keys and types are converted to lower case.
           *
           * <p><b>Note</b>:Setting the 'u' extension via {@link #setExtension}
           * replaces all Unicode locale keywords with those defined in the
           * extension.
           *
           * @param key the Unicode locale key
           * @param type the Unicode locale type
           * @return This builder.
           * @throws IllformedLocaleException if <code>key</code> or <code>type</code>
           * is ill-formed
           * @throws NullPointerException if <code>key</code> is null
           * @see #setExtension(char, String)
           */
          public Builder setUnicodeLocaleKeyword(String key, String type) {
              try {
                  localeBuilder.setUnicodeLocaleKeyword(key, type);
              } catch (LocaleSyntaxException e) {
                  throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
              }
              return this;
          }
  
          /**
           * Adds a unicode locale attribute, if not already present, otherwise
           * has no effect.  The attribute must not be null and must be <a
           * href="./Locale.html#def_locale_extension">well-formed</a> or an exception
           * is thrown.
           *
           * @param attribute the attribute
           * @return This builder.
           * @throws NullPointerException if <code>attribute</code> is null
           * @throws IllformedLocaleException if <code>attribute</code> is ill-formed
           * @see #setExtension(char, String)
           */
          public Builder addUnicodeLocaleAttribute(String attribute) {
              try {
                  localeBuilder.addUnicodeLocaleAttribute(attribute);
              } catch (LocaleSyntaxException e) {
                  throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
              }
              return this;
          }
  
          /**
           * Removes a unicode locale attribute, if present, otherwise has no
           * effect.  The attribute must not be null and must be <a
           * href="./Locale.html#def_locale_extension">well-formed</a> or an exception
           * is thrown.
           *
           * <p>Attribute comparision for removal is case-insensitive.
           *
           * @param attribute the attribute
           * @return This builder.
           * @throws NullPointerException if <code>attribute</code> is null
           * @throws IllformedLocaleException if <code>attribute</code> is ill-formed
           * @see #setExtension(char, String)
           */
          public Builder removeUnicodeLocaleAttribute(String attribute) {
              // BEGIN Android-added: removeUnicodeLocaleAttribute(null) is documented to throw NPE.
              // This could probably be contributed back to upstream. http://b/110752069
              if (attribute == null) {
                  throw new NullPointerException("attribute == null");
              }
              // END Android-added: removeUnicodeLocaleAttribute(null) is documented to throw NPE.
  
              try {
                  localeBuilder.removeUnicodeLocaleAttribute(attribute);
              } catch (LocaleSyntaxException e) {
                  throw new IllformedLocaleException(e.getMessage(), e.getErrorIndex());
              }
              return this;
          }
  
          /**
           * Resets the builder to its initial, empty state.
           *
           * @return This builder.
           */
          public Builder clear() {
              localeBuilder.clear();
              return this;
          }
  
          /**
           * Resets the extensions to their initial, empty state.
           * Language, script, region and variant are unchanged.
           *
           * @return This builder.
           * @see #setExtension(char, String)
           */
          public Builder clearExtensions() {
              localeBuilder.clearExtensions();
              return this;
          }
  
          /**
           * Returns an instance of <code>Locale</code> created from the fields set
           * on this builder.
           *
           * <p>This applies the conversions listed in {@link Locale#forLanguageTag}
           * when constructing a Locale. (Grandfathered tags are handled in
           * {@link #setLanguageTag}.)
           *
           * @return A Locale.
           */
          public Locale build() {
              BaseLocale baseloc = localeBuilder.getBaseLocale();
              LocaleExtensions extensions = localeBuilder.getLocaleExtensions();
              if (extensions == null && baseloc.getVariant().length() > 0) {
                  extensions = getCompatibilityExtensions(baseloc.getLanguage(), baseloc.getScript(),
                          baseloc.getRegion(), baseloc.getVariant());
              }
              return Locale.getInstance(baseloc, extensions);
          }
      }
  
      /**
       * This enum provides constants to select a filtering mode for locale
       * matching. Refer to <a href="http://tools.ietf.org/html/rfc4647">RFC 4647
       * Matching of Language Tags</a> for details.
       *
       * <p>As an example, think of two Language Priority Lists each of which
       * includes only one language range and a set of following language tags:
       *
       * <pre>
       *    de (German)
       *    de-DE (German, Germany)
       *    de-Deva (German, in Devanagari script)
       *    de-Deva-DE (German, in Devanagari script, Germany)
       *    de-DE-1996 (German, Germany, orthography of 1996)
       *    de-Latn-DE (German, in Latin script, Germany)
       *    de-Latn-DE-1996 (German, in Latin script, Germany, orthography of 1996)
       * </pre>
       *
       * The filtering method will behave as follows:
       *
       * <table cellpadding=2 summary="Filtering method behavior">
       * <tr>
       * <th>Filtering Mode</th>
       * <th>Language Priority List: {@code "de-DE"}</th>
       * <th>Language Priority List: {@code "de-*-DE"}</th>
       * </tr>
       * <tr>
       * <td valign=top>
       * {@link FilteringMode#AUTOSELECT_FILTERING AUTOSELECT_FILTERING}
       * </td>
       * <td valign=top>
       * Performs <em>basic</em> filtering and returns {@code "de-DE"} and
       * {@code "de-DE-1996"}.
       * </td>
       * <td valign=top>
       * Performs <em>extended</em> filtering and returns {@code "de-DE"},
       * {@code "de-Deva-DE"}, {@code "de-DE-1996"}, {@code "de-Latn-DE"}, and
       * {@code "de-Latn-DE-1996"}.
       * </td>
       * </tr>
       * <tr>
       * <td valign=top>
       * {@link FilteringMode#EXTENDED_FILTERING EXTENDED_FILTERING}
       * </td>
       * <td valign=top>
       * Performs <em>extended</em> filtering and returns {@code "de-DE"},
       * {@code "de-Deva-DE"}, {@code "de-DE-1996"}, {@code "de-Latn-DE"}, and
       * {@code "de-Latn-DE-1996"}.
       * </td>
       * <td valign=top>Same as above.</td>
       * </tr>
       * <tr>
       * <td valign=top>
       * {@link FilteringMode#IGNORE_EXTENDED_RANGES IGNORE_EXTENDED_RANGES}
       * </td>
       * <td valign=top>
       * Performs <em>basic</em> filtering and returns {@code "de-DE"} and
       * {@code "de-DE-1996"}.
       * </td>
       * <td valign=top>
       * Performs <em>basic</em> filtering and returns {@code null} because
       * nothing matches.
       * </td>
       * </tr>
       * <tr>
       * <td valign=top>
       * {@link FilteringMode#MAP_EXTENDED_RANGES MAP_EXTENDED_RANGES}
       * </td>
       * <td valign=top>Same as above.</td>
       * <td valign=top>
       * Performs <em>basic</em> filtering and returns {@code "de-DE"} and
       * {@code "de-DE-1996"} because {@code "de-*-DE"} is mapped to
       * {@code "de-DE"}.
       * </td>
       * </tr>
       * <tr>
       * <td valign=top>
       * {@link FilteringMode#REJECT_EXTENDED_RANGES REJECT_EXTENDED_RANGES}
       * </td>
       * <td valign=top>Same as above.</td>
       * <td valign=top>
       * Throws {@link IllegalArgumentException} because {@code "de-*-DE"} is
       * not a valid basic language range.
       * </td>
       * </tr>
       * </table>
       *
       * @see #filter(List, Collection, FilteringMode)
       * @see #filterTags(List, Collection, FilteringMode)
       *
       * @since 1.8
       */
      public static enum FilteringMode {
          /**
           * Specifies automatic filtering mode based on the given Language
           * Priority List consisting of language ranges. If all of the ranges
           * are basic, basic filtering is selected. Otherwise, extended
           * filtering is selected.
           */
          AUTOSELECT_FILTERING,
  
          /**
           * Specifies extended filtering.
           */
          EXTENDED_FILTERING,
  
          /**
           * Specifies basic filtering: Note that any extended language ranges
           * included in the given Language Priority List are ignored.
           */
          IGNORE_EXTENDED_RANGES,
  
          /**
           * Specifies basic filtering: If any extended language ranges are
           * included in the given Language Priority List, they are mapped to the
           * basic language range. Specifically, a language range starting with a
           * subtag {@code "*"} is treated as a language range {@code "*"}. For
           * example, {@code "*-US"} is treated as {@code "*"}. If {@code "*"} is
           * not the first subtag, {@code "*"} and extra {@code "-"} are removed.
           * For example, {@code "ja-*-JP"} is mapped to {@code "ja-JP"}.
           */
          MAP_EXTENDED_RANGES,
  
          /**
           * Specifies basic filtering: If any extended language ranges are
           * included in the given Language Priority List, the list is rejected
           * and the filtering method throws {@link IllegalArgumentException}.
           */
          REJECT_EXTENDED_RANGES
      };
  
      /**
       * This class expresses a <em>Language Range</em> defined in
       * <a href="http://tools.ietf.org/html/rfc4647">RFC 4647 Matching of
       * Language Tags</a>. A language range is an identifier which is used to
       * select language tag(s) meeting specific requirements by using the
       * mechanisms described in <a href="Locale.html#LocaleMatching">Locale
       * Matching</a>. A list which represents a user's preferences and consists
       * of language ranges is called a <em>Language Priority List</em>.
       *
       * <p>There are two types of language ranges: basic and extended. In RFC
       * 4647, the syntax of language ranges is expressed in
       * <a href="http://tools.ietf.org/html/rfc4234">ABNF</a> as follows:
       * <blockquote>
       * <pre>
       *     basic-language-range    = (1*8ALPHA *("-" 1*8alphanum)) / "*"
       *     extended-language-range = (1*8ALPHA / "*")
       *                               *("-" (1*8alphanum / "*"))
       *     alphanum                = ALPHA / DIGIT
       * </pre>
       * </blockquote>
       * For example, {@code "en"} (English), {@code "ja-JP"} (Japanese, Japan),
       * {@code "*"} (special language range which matches any language tag) are
       * basic language ranges, whereas {@code "*-CH"} (any languages,
       * Switzerland), {@code "es-*"} (Spanish, any regions), and
       * {@code "zh-Hant-*"} (Traditional Chinese, any regions) are extended
       * language ranges.
       *
       * @see #filter
       * @see #filterTags
       * @see #lookup
       * @see #lookupTag
       *
       * @since 1.8
       */
      public static final class LanguageRange {
  
         /**
          * A constant holding the maximum value of weight, 1.0, which indicates
          * that the language range is a good fit for the user.
          */
          public static final double MAX_WEIGHT = 1.0;
  
         /**
          * A constant holding the minimum value of weight, 0.0, which indicates
          * that the language range is not a good fit for the user.
          */
          public static final double MIN_WEIGHT = 0.0;
  
          private final String range;
          private final double weight;
  
          private volatile int hash = 0;
  
          /**
           * Constructs a {@code LanguageRange} using the given {@code range}.
           * Note that no validation is done against the IANA Language Subtag
           * Registry at time of construction.
           *
           * <p>This is equivalent to {@code LanguageRange(range, MAX_WEIGHT)}.
           *
           * @param range a language range
           * @throws NullPointerException if the given {@code range} is
           *     {@code null}
           */
          public LanguageRange(String range) {
              this(range, MAX_WEIGHT);
          }
  
          /**
           * Constructs a {@code LanguageRange} using the given {@code range} and
           * {@code weight}. Note that no validation is done against the IANA
           * Language Subtag Registry at time of construction.
           *
           * @param range  a language range
           * @param weight a weight value between {@code MIN_WEIGHT} and
           *     {@code MAX_WEIGHT}
           * @throws NullPointerException if the given {@code range} is
           *     {@code null}
           * @throws IllegalArgumentException if the given {@code weight} is less
           *     than {@code MIN_WEIGHT} or greater than {@code MAX_WEIGHT}
           */
          public LanguageRange(String range, double weight) {
              if (range == null) {
                  throw new NullPointerException();
              }
              if (weight < MIN_WEIGHT || weight > MAX_WEIGHT) {
                  throw new IllegalArgumentException("weight=" + weight);
              }
  
              range = range.toLowerCase();
  
              // Do syntax check.
              boolean isIllFormed = false;
              String[] subtags = range.split("-");
              if (isSubtagIllFormed(subtags[0], true)
                  || range.endsWith("-")) {
                  isIllFormed = true;
              } else {
                  for (int i = 1; i < subtags.length; i++) {
                      if (isSubtagIllFormed(subtags[i], false)) {
                          isIllFormed = true;
                          break;
                      }
                  }
              }
              if (isIllFormed) {
                  throw new IllegalArgumentException("range=" + range);
              }
  
              this.range = range;
              this.weight = weight;
          }
  
          private static boolean isSubtagIllFormed(String subtag,
                                                   boolean isFirstSubtag) {
              if (subtag.equals("") || subtag.length() > 8) {
                  return true;
              } else if (subtag.equals("*")) {
                  return false;
              }
              char[] charArray = subtag.toCharArray();
              if (isFirstSubtag) { // ALPHA
                  for (char c : charArray) {
                      if (c < 'a' || c > 'z') {
                          return true;
                      }
                  }
              } else { // ALPHA / DIGIT
                  for (char c : charArray) {
                      if (c < '0' || (c > '9' && c < 'a') || c > 'z') {
                          return true;
                      }
                  }
              }
              return false;
          }
  
          /**
           * Returns the language range of this {@code LanguageRange}.
           *
           * @return the language range.
           */
          public String getRange() {
              return range;
          }
  
          /**
           * Returns the weight of this {@code LanguageRange}.
           *
           * @return the weight value.
           */
          public double getWeight() {
              return weight;
          }
  
          /**
           * Parses the given {@code ranges} to generate a Language Priority List.
           *
           * <p>This method performs a syntactic check for each language range in
           * the given {@code ranges} but doesn't do validation using the IANA
           * Language Subtag Registry.
           *
           * <p>The {@code ranges} to be given can take one of the following
           * forms:
           *
           * <pre>
           *   "Accept-Language: ja,en;q=0.4"  (weighted list with Accept-Language prefix)
           *   "ja,en;q=0.4"                   (weighted list)
           *   "ja,en"                         (prioritized list)
           * </pre>
           *
           * In a weighted list, each language range is given a weight value.
           * The weight value is identical to the "quality value" in
           * <a href="http://tools.ietf.org/html/rfc2616">RFC 2616</a>, and it
           * expresses how much the user prefers  the language. A weight value is
           * specified after a corresponding language range followed by
           * {@code ";q="}, and the default weight value is {@code MAX_WEIGHT}
           * when it is omitted.
           *
           * <p>Unlike a weighted list, language ranges in a prioritized list
           * are sorted in the descending order based on its priority. The first
           * language range has the highest priority and meets the user's
           * preference most.
           *
           * <p>In either case, language ranges are sorted in descending order in
           * the Language Priority List based on priority or weight. If a
           * language range appears in the given {@code ranges} more than once,
           * only the first one is included on the Language Priority List.
           *
           * <p>The returned list consists of language ranges from the given
           * {@code ranges} and their equivalents found in the IANA Language
           * Subtag Registry. For example, if the given {@code ranges} is
           * {@code "Accept-Language: iw,en-us;q=0.7,en;q=0.3"}, the elements in
           * the list to be returned are:
           *
           * <pre>
           *  <b>Range</b>                                   <b>Weight</b>
           *    "iw" (older tag for Hebrew)             1.0
           *    "he" (new preferred code for Hebrew)    1.0
           *    "en-us" (English, United States)        0.7
           *    "en" (English)                          0.3
           * </pre>
           *
           * Two language ranges, {@code "iw"} and {@code "he"}, have the same
           * highest priority in the list. By adding {@code "he"} to the user's
           * Language Priority List, locale-matching method can find Hebrew as a
           * matching locale (or language tag) even if the application or system
           * offers only {@code "he"} as a supported locale (or language tag).
           *
           * @param ranges a list of comma-separated language ranges or a list of
           *     language ranges in the form of the "Accept-Language" header
           *     defined in <a href="http://tools.ietf.org/html/rfc2616">RFC
           *     2616</a>
           * @return a Language Priority List consisting of language ranges
           *     included in the given {@code ranges} and their equivalent
           *     language ranges if available. The list is modifiable.
           * @throws NullPointerException if {@code ranges} is null
           * @throws IllegalArgumentException if a language range or a weight
           *     found in the given {@code ranges} is ill-formed
           */
          public static List<LanguageRange> parse(String ranges) {
              return LocaleMatcher.parse(ranges);
          }
  
          /**
           * Parses the given {@code ranges} to generate a Language Priority
           * List, and then customizes the list using the given {@code map}.
           * This method is equivalent to
           * {@code mapEquivalents(parse(ranges), map)}.
           *
           * @param ranges a list of comma-separated language ranges or a list
           *     of language ranges in the form of the "Accept-Language" header
           *     defined in <a href="http://tools.ietf.org/html/rfc2616">RFC
           *     2616</a>
           * @param map a map containing information to customize language ranges
           * @return a Language Priority List with customization. The list is
           *     modifiable.
           * @throws NullPointerException if {@code ranges} is null
           * @throws IllegalArgumentException if a language range or a weight
           *     found in the given {@code ranges} is ill-formed
           * @see #parse(String)
           * @see #mapEquivalents
           */
          public static List<LanguageRange> parse(String ranges,
                                                  Map<String, List<String>> map) {
              return mapEquivalents(parse(ranges), map);
          }
  
          /**
           * Generates a new customized Language Priority List using the given
           * {@code priorityList} and {@code map}. If the given {@code map} is
           * empty, this method returns a copy of the given {@code priorityList}.
           *
           * <p>In the map, a key represents a language range whereas a value is
           * a list of equivalents of it. {@code '*'} cannot be used in the map.
           * Each equivalent language range has the same weight value as its
           * original language range.
           *
           * <pre>
           *  An example of map:
           *    <b>Key</b>                            <b>Value</b>
           *      "zh" (Chinese)                 "zh",
           *                                     "zh-Hans"(Simplified Chinese)
           *      "zh-HK" (Chinese, Hong Kong)   "zh-HK"
           *      "zh-TW" (Chinese, Taiwan)      "zh-TW"
           * </pre>
           *
           * The customization is performed after modification using the IANA
           * Language Subtag Registry.
           *
           * <p>For example, if a user's Language Priority List consists of five
           * language ranges ({@code "zh"}, {@code "zh-CN"}, {@code "en"},
           * {@code "zh-TW"}, and {@code "zh-HK"}), the newly generated Language
           * Priority List which is customized using the above map example will
           * consists of {@code "zh"}, {@code "zh-Hans"}, {@code "zh-CN"},
           * {@code "zh-Hans-CN"}, {@code "en"}, {@code "zh-TW"}, and
           * {@code "zh-HK"}.
           *
           * <p>{@code "zh-HK"} and {@code "zh-TW"} aren't converted to
           * {@code "zh-Hans-HK"} nor {@code "zh-Hans-TW"} even if they are
           * included in the Language Priority List. In this example, mapping
           * is used to clearly distinguish Simplified Chinese and Traditional
           * Chinese.
           *
           * <p>If the {@code "zh"}-to-{@code "zh"} mapping isn't included in the
           * map, a simple replacement will be performed and the customized list
           * won't include {@code "zh"} and {@code "zh-CN"}.
           *
           * @param priorityList user's Language Priority List
           * @param map a map containing information to customize language ranges
           * @return a new Language Priority List with customization. The list is
           *     modifiable.
           * @throws NullPointerException if {@code priorityList} is {@code null}
           * @see #parse(String, Map)
           */
          public static List<LanguageRange> mapEquivalents(
                                                List<LanguageRange>priorityList,
                                                Map<String, List<String>> map) {
              return LocaleMatcher.mapEquivalents(priorityList, map);
          }
  
          /**
           * Returns a hash code value for the object.
           *
           * @return  a hash code value for this object.
           */
          @Override
          public int hashCode() {
              if (hash == 0) {
                  int result = 17;
                  result = 37*result + range.hashCode();
                  long bitsWeight = Double.doubleToLongBits(weight);
                  result = 37*result + (int)(bitsWeight ^ (bitsWeight >>> 32));
                  hash = result;
              }
              return hash;
          }
  
          /**
           * Compares this object to the specified object. The result is true if
           * and only if the argument is not {@code null} and is a
           * {@code LanguageRange} object that contains the same {@code range}
           * and {@code weight} values as this object.
           *
           * @param obj the object to compare with
           * @return  {@code true} if this object's {@code range} and
           *     {@code weight} are the same as the {@code obj}'s; {@code false}
           *     otherwise.
           */
          @Override
          public boolean equals(Object obj) {
              if (this == obj) {
                  return true;
              }
              if (!(obj instanceof LanguageRange)) {
                  return false;
              }
              LanguageRange other = (LanguageRange)obj;
              return hash == other.hash
                     && range.equals(other.range)
                     && weight == other.weight;
          }
      }
  
      /**
       * Returns a list of matching {@code Locale} instances using the filtering
       * mechanism defined in RFC 4647.
       *
       * @param priorityList user's Language Priority List in which each language
       *     tag is sorted in descending order based on priority or weight
       * @param locales {@code Locale} instances used for matching
       * @param mode filtering mode
       * @return a list of {@code Locale} instances for matching language tags
       *     sorted in descending order based on priority or weight, or an empty
       *     list if nothing matches. The list is modifiable.
       * @throws NullPointerException if {@code priorityList} or {@code locales}
       *     is {@code null}
       * @throws IllegalArgumentException if one or more extended language ranges
       *     are included in the given list when
       *     {@link FilteringMode#REJECT_EXTENDED_RANGES} is specified
       *
       * @since 1.8
       */
      public static List<Locale> filter(List<LanguageRange> priorityList,
                                        Collection<Locale> locales,
                                        FilteringMode mode) {
          return LocaleMatcher.filter(priorityList, locales, mode);
      }
  
      /**
       * Returns a list of matching {@code Locale} instances using the filtering
       * mechanism defined in RFC 4647. This is equivalent to
       * {@link #filter(List, Collection, FilteringMode)} when {@code mode} is
       * {@link FilteringMode#AUTOSELECT_FILTERING}.
       *
       * @param priorityList user's Language Priority List in which each language
       *     tag is sorted in descending order based on priority or weight
       * @param locales {@code Locale} instances used for matching
       * @return a list of {@code Locale} instances for matching language tags
       *     sorted in descending order based on priority or weight, or an empty
       *     list if nothing matches. The list is modifiable.
       * @throws NullPointerException if {@code priorityList} or {@code locales}
       *     is {@code null}
       *
       * @since 1.8
       */
      public static List<Locale> filter(List<LanguageRange> priorityList,
                                        Collection<Locale> locales) {
          return filter(priorityList, locales, FilteringMode.AUTOSELECT_FILTERING);
      }
  
      /**
       * Returns a list of matching languages tags using the basic filtering
       * mechanism defined in RFC 4647.
       *
       * @param priorityList user's Language Priority List in which each language
       *     tag is sorted in descending order based on priority or weight
       * @param tags language tags
       * @param mode filtering mode
       * @return a list of matching language tags sorted in descending order
       *     based on priority or weight, or an empty list if nothing matches.
       *     The list is modifiable.
       * @throws NullPointerException if {@code priorityList} or {@code tags} is
       *     {@code null}
       * @throws IllegalArgumentException if one or more extended language ranges
       *     are included in the given list when
       *     {@link FilteringMode#REJECT_EXTENDED_RANGES} is specified
       *
       * @since 1.8
       */
      public static List<String> filterTags(List<LanguageRange> priorityList,
                                            Collection<String> tags,
                                            FilteringMode mode) {
          return LocaleMatcher.filterTags(priorityList, tags, mode);
      }
  
      /**
       * Returns a list of matching languages tags using the basic filtering
       * mechanism defined in RFC 4647. This is equivalent to
       * {@link #filterTags(List, Collection, FilteringMode)} when {@code mode}
       * is {@link FilteringMode#AUTOSELECT_FILTERING}.
       *
       * @param priorityList user's Language Priority List in which each language
       *     tag is sorted in descending order based on priority or weight
       * @param tags language tags
       * @return a list of matching language tags sorted in descending order
       *     based on priority or weight, or an empty list if nothing matches.
       *     The list is modifiable.
       * @throws NullPointerException if {@code priorityList} or {@code tags} is
       *     {@code null}
       *
       * @since 1.8
       */
      public static List<String> filterTags(List<LanguageRange> priorityList,
                                            Collection<String> tags) {
          return filterTags(priorityList, tags, FilteringMode.AUTOSELECT_FILTERING);
      }
  
      /**
       * Returns a {@code Locale} instance for the best-matching language
       * tag using the lookup mechanism defined in RFC 4647.
       *
       * @param priorityList user's Language Priority List in which each language
       *     tag is sorted in descending order based on priority or weight
       * @param locales {@code Locale} instances used for matching
       * @return the best matching <code>Locale</code> instance chosen based on
       *     priority or weight, or {@code null} if nothing matches.
       * @throws NullPointerException if {@code priorityList} or {@code tags} is
       *     {@code null}
       *
       * @since 1.8
       */
      public static Locale lookup(List<LanguageRange> priorityList,
                                  Collection<Locale> locales) {
          return LocaleMatcher.lookup(priorityList, locales);
      }
  
      /**
       * Returns the best-matching language tag using the lookup mechanism
       * defined in RFC 4647.
       *
       * @param priorityList user's Language Priority List in which each language
       *     tag is sorted in descending order based on priority or weight
       * @param tags language tangs used for matching
       * @return the best matching language tag chosen based on priority or
       *     weight, or {@code null} if nothing matches.
       * @throws NullPointerException if {@code priorityList} or {@code tags} is
       *     {@code null}
       *
       * @since 1.8
       */
      public static String lookupTag(List<LanguageRange> priorityList,
                                     Collection<String> tags) {
          return LocaleMatcher.lookupTag(priorityList, tags);
      }
  
  }
  