Source code

001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 * 
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 * 
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.lang3;
018
019import java.util.ArrayList;
020import java.util.Arrays;
021import java.util.Collections;
022import java.util.HashSet;
023import java.util.List;
024import java.util.Locale;
025import java.util.Set;
026import java.util.concurrent.ConcurrentHashMap;
027import java.util.concurrent.ConcurrentMap;
028
029/**
030 * <p>Operations to assist when working with a {@link Locale}.</p>
031 *
032 * <p>This class tries to handle {@code null} input gracefully.
033 * An exception will not be thrown for a {@code null} input.
034 * Each method documents its behaviour in more detail.</p>
035 *
036 * @since 2.2
037 */
038public class LocaleUtils {
039
040    /** Concurrent map of language locales by country. */
041    private static final ConcurrentMap<String, List<Locale>> cLanguagesByCountry = 
042        new ConcurrentHashMap<String, List<Locale>>();
043
044    /** Concurrent map of country locales by language. */
045    private static final ConcurrentMap<String, List<Locale>> cCountriesByLanguage = 
046        new ConcurrentHashMap<String, List<Locale>>();
047
048    /**
049     * <p>{@code LocaleUtils} instances should NOT be constructed in standard programming.
050     * Instead, the class should be used as {@code LocaleUtils.toLocale("en_GB");}.</p>
051     *
052     * <p>This constructor is public to permit tools that require a JavaBean instance
053     * to operate.</p>
054     */
055    public LocaleUtils() {
056      super();
057    }
058
059    //-----------------------------------------------------------------------
060    /**
061     * <p>Converts a String to a Locale.</p>
062     *
063     * <p>This method takes the string format of a locale and creates the
064     * locale object from it.</p>
065     *
066     * <pre>
067     *   LocaleUtils.toLocale("")           = new Locale("", "")
068     *   LocaleUtils.toLocale("en")         = new Locale("en", "")
069     *   LocaleUtils.toLocale("en_GB")      = new Locale("en", "GB")
070     *   LocaleUtils.toLocale("en_GB_xxx")  = new Locale("en", "GB", "xxx")   (#)
071     * </pre>
072     *
073     * <p>(#) The behaviour of the JDK variant constructor changed between JDK1.3 and JDK1.4.
074     * In JDK1.3, the constructor upper cases the variant, in JDK1.4, it doesn't.
075     * Thus, the result from getVariant() may vary depending on your JDK.</p>
076     *
077     * <p>This method validates the input strictly.
078     * The language code must be lowercase.
079     * The country code must be uppercase.
080     * The separator must be an underscore.
081     * The length must be correct.
082     * </p>
083     *
084     * @param str  the locale String to convert, null returns null
085     * @return a Locale, null if null input
086     * @throws IllegalArgumentException if the string is an invalid format
087     * @see Locale#forLanguageTag(String)
088     */
089    public static Locale toLocale(final String str) {
090        if (str == null) {
091            return null;
092        }
093        if (str.isEmpty()) { // LANG-941 - JDK 8 introduced an empty locale where all fields are blank
094            return new Locale(StringUtils.EMPTY, StringUtils.EMPTY);
095        }
096        if (str.contains("#")) { // LANG-879 - Cannot handle Java 7 script & extensions
097            throw new IllegalArgumentException("Invalid locale format: " + str);
098        }
099        final int len = str.length();
100        if (len < 2) {
101            throw new IllegalArgumentException("Invalid locale format: " + str);
102        }
103        final char ch0 = str.charAt(0);
104        if (ch0 == '_') {
105            if (len < 3) {
106                throw new IllegalArgumentException("Invalid locale format: " + str);
107            }
108            final char ch1 = str.charAt(1);
109            final char ch2 = str.charAt(2);
110            if (!Character.isUpperCase(ch1) || !Character.isUpperCase(ch2)) {
111                throw new IllegalArgumentException("Invalid locale format: " + str);
112            }
113            if (len == 3) {
114                return new Locale(StringUtils.EMPTY, str.substring(1, 3));
115            }
116            if (len < 5) {
117                throw new IllegalArgumentException("Invalid locale format: " + str);
118            }
119            if (str.charAt(3) != '_') {
120                throw new IllegalArgumentException("Invalid locale format: " + str);
121            }
122            return new Locale(StringUtils.EMPTY, str.substring(1, 3), str.substring(4));
123        }
124        
125        final String[] split = str.split("_", -1);
126        final int occurrences = split.length -1;
127        switch (occurrences) {
128            case 0:
129                if (StringUtils.isAllLowerCase(str) && (len == 2 || len == 3)) {
130                    return new Locale(str);
131                }
132            throw new IllegalArgumentException("Invalid locale format: " + str);
133                
134            case 1:
135                if (StringUtils.isAllLowerCase(split[0]) &&
136                    (split[0].length() == 2 || split[0].length() == 3) &&
137                     split[1].length() == 2 && StringUtils.isAllUpperCase(split[1])) {
138                    return new Locale(split[0], split[1]);
139                }
140            throw new IllegalArgumentException("Invalid locale format: " + str);
141
142            case 2:
143                if (StringUtils.isAllLowerCase(split[0]) && 
144                    (split[0].length() == 2 || split[0].length() == 3) &&
145                    (split[1].length() == 0 || split[1].length() == 2 && StringUtils.isAllUpperCase(split[1])) &&
146                     split[2].length() > 0) {
147                    return new Locale(split[0], split[1], split[2]);
148                }
149
150                //$FALL-THROUGH$
151            default:
152                throw new IllegalArgumentException("Invalid locale format: " + str);
153        }
154    }
155
156    //-----------------------------------------------------------------------
157    /**
158     * <p>Obtains the list of locales to search through when performing
159     * a locale search.</p>
160     *
161     * <pre>
162     * localeLookupList(Locale("fr","CA","xxx"))
163     *   = [Locale("fr","CA","xxx"), Locale("fr","CA"), Locale("fr")]
164     * </pre>
165     *
166     * @param locale  the locale to start from
167     * @return the unmodifiable list of Locale objects, 0 being locale, not null
168     */
169    public static List<Locale> localeLookupList(final Locale locale) {
170        return localeLookupList(locale, locale);
171    }
172
173    //-----------------------------------------------------------------------
174    /**
175     * <p>Obtains the list of locales to search through when performing
176     * a locale search.</p>
177     *
178     * <pre>
179     * localeLookupList(Locale("fr", "CA", "xxx"), Locale("en"))
180     *   = [Locale("fr","CA","xxx"), Locale("fr","CA"), Locale("fr"), Locale("en"]
181     * </pre>
182     *
183     * <p>The result list begins with the most specific locale, then the
184     * next more general and so on, finishing with the default locale.
185     * The list will never contain the same locale twice.</p>
186     *
187     * @param locale  the locale to start from, null returns empty list
188     * @param defaultLocale  the default locale to use if no other is found
189     * @return the unmodifiable list of Locale objects, 0 being locale, not null
190     */
191    public static List<Locale> localeLookupList(final Locale locale, final Locale defaultLocale) {
192        final List<Locale> list = new ArrayList<Locale>(4);
193        if (locale != null) {
194            list.add(locale);
195            if (locale.getVariant().length() > 0) {
196                list.add(new Locale(locale.getLanguage(), locale.getCountry()));
197            }
198            if (locale.getCountry().length() > 0) {
199                list.add(new Locale(locale.getLanguage(), StringUtils.EMPTY));
200            }
201            if (list.contains(defaultLocale) == false) {
202                list.add(defaultLocale);
203            }
204        }
205        return Collections.unmodifiableList(list);
206    }
207
208    //-----------------------------------------------------------------------
209    /**
210     * <p>Obtains an unmodifiable list of installed locales.</p>
211     * 
212     * <p>This method is a wrapper around {@link Locale#getAvailableLocales()}.
213     * It is more efficient, as the JDK method must create a new array each
214     * time it is called.</p>
215     *
216     * @return the unmodifiable list of available locales
217     */
218    public static List<Locale> availableLocaleList() {
219        return SyncAvoid.AVAILABLE_LOCALE_LIST;
220    }
221
222    //-----------------------------------------------------------------------
223    /**
224     * <p>Obtains an unmodifiable set of installed locales.</p>
225     * 
226     * <p>This method is a wrapper around {@link Locale#getAvailableLocales()}.
227     * It is more efficient, as the JDK method must create a new array each
228     * time it is called.</p>
229     *
230     * @return the unmodifiable set of available locales
231     */
232    public static Set<Locale> availableLocaleSet() {
233        return SyncAvoid.AVAILABLE_LOCALE_SET;
234    }
235
236    //-----------------------------------------------------------------------
237    /**
238     * <p>Checks if the locale specified is in the list of available locales.</p>
239     *
240     * @param locale the Locale object to check if it is available
241     * @return true if the locale is a known locale
242     */
243    public static boolean isAvailableLocale(final Locale locale) {
244        return availableLocaleList().contains(locale);
245    }
246
247    //-----------------------------------------------------------------------
248    /**
249     * <p>Obtains the list of languages supported for a given country.</p>
250     *
251     * <p>This method takes a country code and searches to find the
252     * languages available for that country. Variant locales are removed.</p>
253     *
254     * @param countryCode  the 2 letter country code, null returns empty
255     * @return an unmodifiable List of Locale objects, not null
256     */
257    public static List<Locale> languagesByCountry(final String countryCode) {
258        if (countryCode == null) {
259            return Collections.emptyList();
260        }
261        List<Locale> langs = cLanguagesByCountry.get(countryCode);
262        if (langs == null) {
263            langs = new ArrayList<Locale>();
264            final List<Locale> locales = availableLocaleList();
265            for (int i = 0; i < locales.size(); i++) {
266                final Locale locale = locales.get(i);
267                if (countryCode.equals(locale.getCountry()) &&
268                        locale.getVariant().isEmpty()) {
269                    langs.add(locale);
270                }
271            }
272            langs = Collections.unmodifiableList(langs);
273            cLanguagesByCountry.putIfAbsent(countryCode, langs);
274            langs = cLanguagesByCountry.get(countryCode);
275        }
276        return langs;
277    }
278
279    //-----------------------------------------------------------------------
280    /**
281     * <p>Obtains the list of countries supported for a given language.</p>
282     * 
283     * <p>This method takes a language code and searches to find the
284     * countries available for that language. Variant locales are removed.</p>
285     *
286     * @param languageCode  the 2 letter language code, null returns empty
287     * @return an unmodifiable List of Locale objects, not null
288     */
289    public static List<Locale> countriesByLanguage(final String languageCode) {
290        if (languageCode == null) {
291            return Collections.emptyList();
292        }
293        List<Locale> countries = cCountriesByLanguage.get(languageCode);
294        if (countries == null) {
295            countries = new ArrayList<Locale>();
296            final List<Locale> locales = availableLocaleList();
297            for (int i = 0; i < locales.size(); i++) {
298                final Locale locale = locales.get(i);
299                if (languageCode.equals(locale.getLanguage()) &&
300                        locale.getCountry().length() != 0 &&
301                        locale.getVariant().isEmpty()) {
302                    countries.add(locale);
303                }
304            }
305            countries = Collections.unmodifiableList(countries);
306            cCountriesByLanguage.putIfAbsent(languageCode, countries);
307            countries = cCountriesByLanguage.get(languageCode);
308        }
309        return countries;
310    }
311
312    //-----------------------------------------------------------------------
313    // class to avoid synchronization (Init on demand)
314    static class SyncAvoid {
315        /** Unmodifiable list of available locales. */
316        private static final List<Locale> AVAILABLE_LOCALE_LIST;
317        /** Unmodifiable set of available locales. */
318        private static final Set<Locale> AVAILABLE_LOCALE_SET;
319        
320        static {
321            final List<Locale> list = new ArrayList<Locale>(Arrays.asList(Locale.getAvailableLocales()));  // extra safe
322            AVAILABLE_LOCALE_LIST = Collections.unmodifiableList(list);
323            AVAILABLE_LOCALE_SET = Collections.unmodifiableSet(new HashSet<Locale>(list));
324        }
325    }
326
327}