locale.java

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/*
 * @(#)Locale.java	1.69 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

/*
 * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
 * (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved
 *
 * The original version of this source code and documentation
 * is copyrighted and owned by Taligent, Inc., a wholly-owned
 * subsidiary of IBM. These materials are provided under terms
 * of a License Agreement between Taligent and Sun. This technology
 * is protected by multiple US and International patents.
 *
 * This notice and attribution to Taligent may not be removed.
 * Taligent is a registered trademark of Taligent, Inc.
 *
 */

package java.util;

import java.io.*;
import java.security.AccessController;
import java.text.MessageFormat;
import sun.security.action.GetPropertyAction;
import sun.text.resources.LocaleData;

/**
 *
 * A <code>Locale</code> object represents a specific geographical, political,
 * or cultural region. An operation that requires a <code>Locale</code> to perform
 * its task is called <em>locale-sensitive</em> and uses the <code>Locale</code>
 * to tailor information for the user. For example, displaying a number
 * is a locale-sensitive operation--the number should be formatted
 * according to the customs/conventions of the user's native country,
 * region, or culture.
 *
 * <P>
 * Create a <code>Locale</code> object using the constructors in this class:
 * <blockquote>
 * <pre>
 * Locale(String language)
 * Locale(String language, String country)
 * Locale(String language, String country, String variant)
 * </pre>
 * </blockquote>
 * The language argument is a valid <STRONG>ISO Language Code.</STRONG> 
 * These codes are the lower-case, two-letter codes as defined by ISO-639.
 * You can find a full list of these codes at a number of sites, such as:
 * <BR><a href ="http://www.ics.uci.edu/pub/ietf/http/related/iso639.txt">
 * <code>http://www.ics.uci.edu/pub/ietf/http/related/iso639.txt</code></a>
 *
 * <P>
 * The country argument is a valid <STRONG>ISO Country Code.</STRONG> These 
 * codes are the upper-case, two-letter codes as defined by ISO-3166.
 * You can find a full list of these codes at a number of sites, such as:
 * <BR><a href="http://www.chemie.fu-berlin.de/diverse/doc/ISO_3166.html">
 * <code>http://www.chemie.fu-berlin.de/diverse/doc/ISO_3166.html</code></a>
 *
 * <P>
 * The variant argument is a vendor or browser-specific code.
 * For example, use WIN for Windows, MAC for Macintosh, and POSIX for POSIX.
 * Where there are two variants, separate them with an underscore, and
 * put the most important one first. For example, a Traditional Spanish collation 
 * might construct a locale with parameters for language, country and variant as: 
 * "es", "ES", "Traditional_WIN".
 *
 * <P>
 * Because a <code>Locale</code> object is just an identifier for a region,
 * no validity check is performed when you construct a <code>Locale</code>.
 * If you want to see whether particular resources are available for the
 * <code>Locale</code> you construct, you must query those resources. For
 * example, ask the <code>NumberFormat</code> for the locales it supports
 * using its <code>getAvailableLocales</code> method.
 * <BR><STRONG>Note:</STRONG> When you ask for a resource for a particular
 * locale, you get back the best available match, not necessarily
 * precisely what you asked for. For more information, look at
 * {@link ResourceBundle}.
 *
 * <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>
 *
 * <P>
 * Once you've created a <code>Locale</code> you can query it for information about
 * itself. Use <code>getCountry</code> to get the ISO Country Code and
 * <code>getLanguage</code> to get the ISO 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 locale and one
 * that uses the locale specified as an argument.
 *
 * <P>
 * The Java 2 platform provides a number of classes that perform locale-sensitive
 * operations. For example, the <code>NumberFormat</code> class formats
 * numbers, currency, or percentages in a locale-sensitive manner. Classes
 * such as <code>NumberFormat</code> have a number of 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>
 * These methods have two variants; one with an explicit locale
 * and one without; the latter using the default 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.
 *
 * <P>
 * Each class that performs locale-sensitive operations allows you
 * to get all the available objects of that type. You can sift
 * through these objects by language, country, or variant,
 * and use the display names to present a menu to the user.
 * For example, you can create a menu of all the collation objects
 * suitable for a given language. Such classes must implement these
 * three class methods:
 * <blockquote>
 * <pre>
 * public static Locale[] getAvailableLocales()
 * public static String getDisplayName(Locale objectLocale,
 *                                     Locale displayLocale)
 * public static final String getDisplayName(Locale objectLocale)
 *     // getDisplayName will throw MissingResourceException if the locale
 *     // is not one of the available locales.
 * </pre>
 * </blockquote>
 *
 * @see         ResourceBundle
 * @see         java.text.Format
 * @see         java.text.NumberFormat
 * @see         java.text.Collator
 * @version     1.69, 01/23/03
 * @author      Mark Davis
 * @since       1.1
 */

public final class Locale implements Cloneable, Serializable {

    /** Useful constant for language.
     */
    static public final Locale ENGLISH = new Locale("en","","");

    /** Useful constant for language.
     */
    static public final Locale FRENCH = new Locale("fr","","");

    /** Useful constant for language.
     */
    static public final Locale GERMAN = new Locale("de","","");

    /** Useful constant for language.
     */
    static public final Locale ITALIAN = new Locale("it","","");

    /** Useful constant for language.
     */
    static public final Locale JAPANESE = new Locale("ja","","");

    /** Useful constant for language.
     */
    static public final Locale KOREAN = new Locale("ko","","");

    /** Useful constant for language.
     */
    static public final Locale CHINESE = new Locale("zh","","");

    /** Useful constant for language.
     */
    static public final Locale SIMPLIFIED_CHINESE = new Locale("zh","CN","");

    /** Useful constant for language.
     */
    static public final Locale TRADITIONAL_CHINESE = new Locale("zh","TW","");

    /** Useful constant for country.
     */
    static public final Locale FRANCE = new Locale("fr","FR","");

    /** Useful constant for country.
     */
    static public final Locale GERMANY = new Locale("de","DE","");

    /** Useful constant for country.
     */
    static public final Locale ITALY = new Locale("it","IT","");

    /** Useful constant for country.
     */
    static public final Locale JAPAN = new Locale("ja","JP","");

    /** Useful constant for country.
     */
    static public final Locale KOREA = new Locale("ko","KR","");

    /** Useful constant for country.
     */
    static public final Locale CHINA = new Locale("zh","CN","");

    /** Useful constant for country.
     */
    static public final Locale PRC = new Locale("zh","CN","");

    /** Useful constant for country.
     */
    static public final Locale TAIWAN = new Locale("zh","TW","");

    /** Useful constant for country.
     */
    static public final Locale UK = new Locale("en","GB","");

    /** Useful constant for country.
     */
    static public final Locale US = new Locale("en","US","");

    /** Useful constant for country.
     */
    static public final Locale CANADA = new Locale("en","CA","");

    /** Useful constant for country.
     */
    static public final Locale CANADA_FRENCH = new Locale("fr","CA","");

    /** serialization ID
     */
    static final long serialVersionUID = 9149081749638150636L;

    /**
     * Construct a locale from language, country, variant.
     * NOTE:  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.
     * @param language lowercase two-letter ISO-639 code.
     * @param country uppercase two-letter ISO-3166 code.
     * @param variant vendor and browser specific code. See class description.
     * @exception NullPointerException thrown if any argument is null.
     */
    public Locale(String language, String country, String variant) {
        this.language = convertOldISOCodes(language);
        this.country = toUpperCase(country).intern();
        this.variant = variant.intern();
    }

    /**
     * Construct a locale from language, country.
     * NOTE:  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.
     * @param language lowercase two-letter ISO-639 code.
     * @param country uppercase two-letter ISO-3166 code.
     * @exception NullPointerException thrown if either argument is null.
     */
    public Locale(String language, String country) {
        this(language, country, "");
    }

    /**
     * Construct a locale from a language code.
     * NOTE:  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.
     * @param language lowercase two-letter ISO-639 code.
     * @exception NullPointerException thrown if argument is null.
     * @since 1.4
     */
    public Locale(String language) {