001 /* LocaleServiceProvider.java -- Superclass of locale SPIs
002 Copyright (C) 2007 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
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012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
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017 along with GNU Classpath; see the file COPYING. If not, write to the
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019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038 package java.util.spi;
039
040 import java.util.Locale;
041
042 /**
043 * <p>
044 * This is the superclass of all the {@link Locale} service
045 * provider interfaces or SPIs. The locale SPIs are used
046 * to allow for the provision of additional support for
047 * locale-specific data. The runtime environment has its
048 * own collection of locale data, but these interfaces allow
049 * this to be extended by external classes.
050 * </p>
051 * <p>
052 * Service providers are created as concrete implementations
053 * of these interfaces, and accessed using the extension
054 * mechanism, realised by {@link ServiceLoader}. When a factory
055 * method of one of the locale-specific classes (such as
056 * {@link java.text.DateFormatSymbols} or {@link java.util.Currency})
057 * is called, the runtime environment is first asked to
058 * provide data for the specified locale. If the runtime
059 * environment fails to provide this, then the offer is
060 * made to service providers which implement the appropriate
061 * interface.
062 * </p>
063 * <p>
064 * Each provider implements the method specified by this
065 * class, {@link #getAvailableLocales()}. This method is
066 * called first to determine whether the provider will be of
067 * any use in providing data for the specified locale. If
068 * a provider is found to be capable, then a more specific
069 * method appropriate to the class requiring the data will
070 * be called. In the case of {@link java.text.DateFormatSymbols},
071 * this would be
072 * {@link java.text.spi.DateFormatSymbols#getInstance(Locale)}.
073 * </p>
074 * <p>
075 * If neither a service provider nor the runtime environment
076 * itself can fulfill the request, a fallback procedure is
077 * engaged. The locale is modified by applying the first
078 * applicable rule:
079 * </p>
080 * <ol>
081 * <li>If the variant contains a <code>'_'</code>, then
082 * this and everything following it is trimmed.</li>
083 * <li>If the variant is non-empty, it is converted to
084 * an empty string.</li>
085 * <li>If the country is non-empty, it is converted to
086 * an empty string.</li>
087 * <li>If the language is non-empty, it is converted to
088 * an empty string.</li>
089 * </ol>
090 * <p>
091 * The modified locale is then used to start the same
092 * process again. The root locale (@link java.util.Locale#ROOT}
093 * must be supported by the runtime environment in order
094 * to terminate this cycle.
095 * </p>
096 * <p>
097 * Note that any names returned by the providers may
098 * be <code>null</code>. Returning a <code>null</code>
099 * name is considered equivalent to not supporting a
100 * particular locale.
101 * </p>
102 *
103 * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
104 * @since 1.6
105 */
106 public abstract class LocaleServiceProvider
107 {
108
109 /**
110 * Constructs a new {@link LocaleServiceProvider}.
111 * Provided for implicit invocation by subclasses.
112 */
113 protected LocaleServiceProvider()
114 {
115 }
116
117 /**
118 * Returns an array of {@link Locale} instances,
119 * for which the provider can supply localized data.
120 *
121 * @return an array of supported locales.
122 */
123 public abstract Locale[] getAvailableLocales();
124
125 }