/*

 * Copyright 2005-2006 Sun Microsystems, Inc.  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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

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 */

package java.util.spi;

import java.util.Locale;

/**

 * <p>

 * This is the super class of all the locale sensitive service provider

 * interfaces (SPIs).

 * <p>

 * Locale sensitive  service provider interfaces are interfaces that

 * correspond to locale sensitive classes in the <code>java.text</code>

 * and <code>java.util</code> packages. The interfaces enable the

 * construction of locale sensitive objects and the retrieval of

 * localized names for these packages. Locale sensitive factory methods

 * and methods for name retrieval in the <code>java.text</code> and

 * <code>java.util</code> packages use implementations of the provider

 * interfaces to offer support for locales beyond the set of locales

 * supported by the Java runtime environment itself.

 * <p>

 * <h4>Packaging of Locale Sensitive Service Provider Implementations</h4>

 * Implementations of these locale sensitive services are packaged using the

 * <a href="../../../../technotes/guides/extensions/index.html">Java Extension Mechanism</a>

 * as installed extensions.  A provider identifies itself with a

 * provider-configuration file in the resource directory META-INF/services,

 * using the fully qualified provider interface class name as the file name.

 * The file should contain a list of fully-qualified concrete provider class names,

 * one per line. A line is terminated by any one of a line feed ('\n'), a carriage

 * return ('\r'), or a carriage return followed immediately by a line feed. Space

 * and tab characters surrounding each name, as well as blank lines, are ignored.

 * The comment character is '#' ('\u0023'); on each line all characters following

 * the first comment character are ignored. The file must be encoded in UTF-8.

 * <p>

 * If a particular concrete provider class is named in more than one configuration

 * file, or is named in the same configuration file more than once, then the

 * duplicates will be ignored. The configuration file naming a particular provider

 * need not be in the same jar file or other distribution unit as the provider itself.

 * The provider must be accessible from the same class loader that was initially

 * queried to locate the configuration file; this is not necessarily the class loader

 * that loaded the file.

 * <p>

 * For example, an implementation of the

 * {@link java.text.spi.DateFormatProvider DateFormatProvider} class should

 * take the form of a jar file which contains the file:

 * <pre>

 * META-INF/services/java.text.spi.DateFormatProvider

 * </pre>

 * And the file <code>java.text.spi.DateFormatProvider</code> should have

 * a line such as:

 * <pre>

 * <code>com.foo.DateFormatProviderImpl</code>

 * </pre>

 * which is the fully qualified class name of the class implementing

 * <code>DateFormatProvider</code>.

 * <h4>Invocation of Locale Sensitive Services</h4>

 * <p>

 * Locale sensitive factory methods and methods for name retrieval in the

 * <code>java.text</code> and <code>java.util</code> packages invoke

 * service provider methods when needed to support the requested locale.

 * The methods first check whether the Java runtime environment itself

 * supports the requested locale, and use its support if available.

 * Otherwise, they call the <code>getAvailableLocales()</code> methods of

 * installed providers for the appropriate interface to find one that

 * supports the requested locale. If such a provider is found, its other

 * methods are called to obtain the requested object or name. If neither

 * the Java runtime environment itself nor an installed provider supports

 * the requested locale, a fallback locale is constructed by replacing the

 * first of the variant, country, or language strings of the locale that's

 * not an empty string with an empty string, and the lookup process is

 * restarted. In the case that the variant contains one or more '_'s, the

 * fallback locale is constructed by replacing the variant with a new variant

 * which eliminates the last '_' and the part following it.  Even if a

 * fallback occurs, methods that return requested objects or name are

 * invoked with the original locale before the fallback.The Java runtime

 * environment must support the root locale for all locale sensitive services

 * in order to guarantee that this process terminates.

 * <p>

 * Providers of names (but not providers of other objects) are allowed to

 * return null for some name requests even for locales that they claim to

 * support by including them in their return value for

 * <code>getAvailableLocales</code>. Similarly, the Java runtime

 * environment itself may not have all names for all locales that it

 * supports. This is because the sets of objects for which names are

 * requested can be large and vary over time, so that it's not always

 * feasible to cover them completely. If the Java runtime environment or a

 * provider returns null instead of a name, the lookup will proceed as

 * described above as if the locale was not supported.

 *

 * @since        1.6

 */

public abstract class LocaleServiceProvider {

    /**

     * Sole constructor.  (For invocation by subclass constructors, typically

     * implicit.)

     */

    protected LocaleServiceProvider() {

    }

    /**

     * Returns an array of all locales for which this locale service provider

     * can provide localized objects or names.

     *

     * @return An array of all locales for which this locale service provider

     * can provide localized objects or names.

     */

    public abstract Locale[] getAvailableLocales();

}