Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.commons.lang3; import java.util.ArrayList; import java.util.Arrays; import java.util.Collections; import java.util.HashSet; import java.util.List; import java.util.Locale; import java.util.Set; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentMap; /** * <p>Operations to assist when working with a {@link Locale}.</p> * * <p>This class tries to handle {@code null} input gracefully. * An exception will not be thrown for a {@code null} input. * Each method documents its behaviour in more detail.</p> * * @since 2.2 * @version $Id$ */ public class LocaleUtils { /** Concurrent map of language locales by country. */ private static final ConcurrentMap<String, List<Locale>> cLanguagesByCountry = new ConcurrentHashMap<String, List<Locale>>(); /** Concurrent map of country locales by language. */ private static final ConcurrentMap<String, List<Locale>> cCountriesByLanguage = new ConcurrentHashMap<String, List<Locale>>(); /** * <p>{@code LocaleUtils} instances should NOT be constructed in standard programming. * Instead, the class should be used as {@code LocaleUtils.toLocale("en_GB");}.</p> * * <p>This constructor is public to permit tools that require a JavaBean instance * to operate.</p> */ public LocaleUtils() { super(); } //----------------------------------------------------------------------- /** * <p>Converts a String to a Locale.</p> * * <p>This method takes the string format of a locale and creates the * locale object from it.</p> * * <pre> * LocaleUtils.toLocale("") = new Locale("", "") * LocaleUtils.toLocale("en") = new Locale("en", "") * LocaleUtils.toLocale("en_GB") = new Locale("en", "GB") * LocaleUtils.toLocale("en_GB_xxx") = new Locale("en", "GB", "xxx") (#) * </pre> * * <p>(#) The behaviour of the JDK variant constructor changed between JDK1.3 and JDK1.4. * In JDK1.3, the constructor upper cases the variant, in JDK1.4, it doesn't. * Thus, the result from getVariant() may vary depending on your JDK.</p> * * <p>This method validates the input strictly. * The language code must be lowercase. * The country code must be uppercase. * The separator must be an underscore. * The length must be correct. * </p> * * @param str the locale String to convert, null returns null * @return a Locale, null if null input * @throws IllegalArgumentException if the string is an invalid format * @see Locale#forLanguageTag(String) */ public static Locale toLocale(final String str) { if (str == null) { return null; } if (str.isEmpty()) { // LANG-941 - JDK 8 introduced an empty locale where all fields are blank return new Locale("", ""); } if (str.contains("#")) { // LANG-879 - Cannot handle Java 7 script & extensions throw new IllegalArgumentException("Invalid locale format: " + str); } final int len = str.length(); if (len < 2) { throw new IllegalArgumentException("Invalid locale format: " + str); } final char ch0 = str.charAt(0); if (ch0 == '_') { if (len < 3) { throw new IllegalArgumentException("Invalid locale format: " + str); } final char ch1 = str.charAt(1); final char ch2 = str.charAt(2); if (!Character.isUpperCase(ch1) || !Character.isUpperCase(ch2)) { throw new IllegalArgumentException("Invalid locale format: " + str); } if (len == 3) { return new Locale("", str.substring(1, 3)); } if (len < 5) { throw new IllegalArgumentException("Invalid locale format: " + str); } if (str.charAt(3) != '_') { throw new IllegalArgumentException("Invalid locale format: " + str); } return new Locale("", str.substring(1, 3), str.substring(4)); } final String[] split = str.split("_", -1); final int occurrences = split.length - 1; switch (occurrences) { case 0: if (StringUtils.isAllLowerCase(str) && (len == 2 || len == 3)) { return new Locale(str); } throw new IllegalArgumentException("Invalid locale format: " + str); case 1: if (StringUtils.isAllLowerCase(split[0]) && (split[0].length() == 2 || split[0].length() == 3) && split[1].length() == 2 && StringUtils.isAllUpperCase(split[1])) { return new Locale(split[0], split[1]); } throw new IllegalArgumentException("Invalid locale format: " + str); case 2: if (StringUtils.isAllLowerCase(split[0]) && (split[0].length() == 2 || split[0].length() == 3) && (split[1].length() == 0 || (split[1].length() == 2 && StringUtils.isAllUpperCase(split[1]))) && split[2].length() > 0) { return new Locale(split[0], split[1], split[2]); } //$FALL-THROUGH$ default: throw new IllegalArgumentException("Invalid locale format: " + str); } } //----------------------------------------------------------------------- /** * <p>Obtains the list of locales to search through when performing * a locale search.</p> * * <pre> * localeLookupList(Locale("fr","CA","xxx")) * = [Locale("fr","CA","xxx"), Locale("fr","CA"), Locale("fr")] * </pre> * * @param locale the locale to start from * @return the unmodifiable list of Locale objects, 0 being locale, not null */ public static List<Locale> localeLookupList(final Locale locale) { return localeLookupList(locale, locale); } //----------------------------------------------------------------------- /** * <p>Obtains the list of locales to search through when performing * a locale search.</p> * * <pre> * localeLookupList(Locale("fr", "CA", "xxx"), Locale("en")) * = [Locale("fr","CA","xxx"), Locale("fr","CA"), Locale("fr"), Locale("en"] * </pre> * * <p>The result list begins with the most specific locale, then the * next more general and so on, finishing with the default locale. * The list will never contain the same locale twice.</p> * * @param locale the locale to start from, null returns empty list * @param defaultLocale the default locale to use if no other is found * @return the unmodifiable list of Locale objects, 0 being locale, not null */ public static List<Locale> localeLookupList(final Locale locale, final Locale defaultLocale) { final List<Locale> list = new ArrayList<Locale>(4); if (locale != null) { list.add(locale); if (locale.getVariant().length() > 0) { list.add(new Locale(locale.getLanguage(), locale.getCountry())); } if (locale.getCountry().length() > 0) { list.add(new Locale(locale.getLanguage(), "")); } if (list.contains(defaultLocale) == false) { list.add(defaultLocale); } } return Collections.unmodifiableList(list); } //----------------------------------------------------------------------- /** * <p>Obtains an unmodifiable list of installed locales.</p> * * <p>This method is a wrapper around {@link Locale#getAvailableLocales()}. * It is more efficient, as the JDK method must create a new array each * time it is called.</p> * * @return the unmodifiable list of available locales */ public static List<Locale> availableLocaleList() { return SyncAvoid.AVAILABLE_LOCALE_LIST; } //----------------------------------------------------------------------- /** * <p>Obtains an unmodifiable set of installed locales.</p> * * <p>This method is a wrapper around {@link Locale#getAvailableLocales()}. * It is more efficient, as the JDK method must create a new array each * time it is called.</p> * * @return the unmodifiable set of available locales */ public static Set<Locale> availableLocaleSet() { return SyncAvoid.AVAILABLE_LOCALE_SET; } //----------------------------------------------------------------------- /** * <p>Checks if the locale specified is in the list of available locales.</p> * * @param locale the Locale object to check if it is available * @return true if the locale is a known locale */ public static boolean isAvailableLocale(final Locale locale) { return availableLocaleList().contains(locale); } //----------------------------------------------------------------------- /** * <p>Obtains the list of languages supported for a given country.</p> * * <p>This method takes a country code and searches to find the * languages available for that country. Variant locales are removed.</p> * * @param countryCode the 2 letter country code, null returns empty * @return an unmodifiable List of Locale objects, not null */ public static List<Locale> languagesByCountry(final String countryCode) { if (countryCode == null) { return Collections.emptyList(); } List<Locale> langs = cLanguagesByCountry.get(countryCode); if (langs == null) { langs = new ArrayList<Locale>(); final List<Locale> locales = availableLocaleList(); for (int i = 0; i < locales.size(); i++) { final Locale locale = locales.get(i); if (countryCode.equals(locale.getCountry()) && locale.getVariant().isEmpty()) { langs.add(locale); } } langs = Collections.unmodifiableList(langs); cLanguagesByCountry.putIfAbsent(countryCode, langs); langs = cLanguagesByCountry.get(countryCode); } return langs; } //----------------------------------------------------------------------- /** * <p>Obtains the list of countries supported for a given language.</p> * * <p>This method takes a language code and searches to find the * countries available for that language. Variant locales are removed.</p> * * @param languageCode the 2 letter language code, null returns empty * @return an unmodifiable List of Locale objects, not null */ public static List<Locale> countriesByLanguage(final String languageCode) { if (languageCode == null) { return Collections.emptyList(); } List<Locale> countries = cCountriesByLanguage.get(languageCode); if (countries == null) { countries = new ArrayList<Locale>(); final List<Locale> locales = availableLocaleList(); for (int i = 0; i < locales.size(); i++) { final Locale locale = locales.get(i); if (languageCode.equals(locale.getLanguage()) && locale.getCountry().length() != 0 && locale.getVariant().isEmpty()) { countries.add(locale); } } countries = Collections.unmodifiableList(countries); cCountriesByLanguage.putIfAbsent(languageCode, countries); countries = cCountriesByLanguage.get(languageCode); } return countries; } //----------------------------------------------------------------------- // class to avoid synchronization (Init on demand) static class SyncAvoid { /** Unmodifiable list of available locales. */ private static final List<Locale> AVAILABLE_LOCALE_LIST; /** Unmodifiable set of available locales. */ private static final Set<Locale> AVAILABLE_LOCALE_SET; static { final List<Locale> list = new ArrayList<Locale>(Arrays.asList(Locale.getAvailableLocales())); // extra safe AVAILABLE_LOCALE_LIST = Collections.unmodifiableList(list); AVAILABLE_LOCALE_SET = Collections.unmodifiableSet(new HashSet<Locale>(list)); } } }