Obtains an unmodifiable set of installed locales.
/*
* 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.
*/
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
/**
* <p>Operations to assist when working with a {@link Locale}.</p>
*
* <p>This class tries to handle <code>null</code> input gracefully.
* An exception will not be thrown for a <code>null</code> input.
* Each method documents its behaviour in more detail.</p>
*
* @author Stephen Colebourne
* @since 2.2
* @version $Id: LocaleUtils.java 534277 2007-05-01 23:50:01Z bayard $
*/
public class LocaleUtils {
/** Unmodifiable list of available locales. */
private static final List cAvailableLocaleList;
/** Unmodifiable set of available locales. */
private static Set cAvailableLocaleSet;
/** Unmodifiable map of language locales by country. */
private static final Map cLanguagesByCountry = Collections.synchronizedMap(new HashMap());
/** Unmodifiable map of country locales by language. */
private static final Map cCountriesByLanguage = Collections.synchronizedMap(new HashMap());
static {
List list = Arrays.asList(Locale.getAvailableLocales());
cAvailableLocaleList = Collections.unmodifiableList(list);
}
/**
* <p><code>LocaleUtils</code> instances should NOT be constructed in standard programming.
* Instead, the class should be used as <code>LocaleUtils.toLocale("en_GB");</code>.</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("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
*/
public static Locale toLocale(String str) {
if (str == null) {
return null;
}
int len = str.length();
if (len != 2 && len != 5 && len < 7) {
throw new IllegalArgumentException("Invalid locale format: " + str);
}
char ch0 = str.charAt(0);
char ch1 = str.charAt(1);
if (ch0 < 'a' || ch0 > 'z' || ch1 < 'a' || ch1 > 'z') {
throw new IllegalArgumentException("Invalid locale format: " + str);
}
if (len == 2) {
return new Locale(str, "");
} else {
if (str.charAt(2) != '_') {
throw new IllegalArgumentException("Invalid locale format: " + str);
}
char ch3 = str.charAt(3);
if (ch3 == '_') {
return new Locale(str.substring(0, 2), "", str.substring(4));
}
char ch4 = str.charAt(4);
if (ch3 < 'A' || ch3 > 'Z' || ch4 < 'A' || ch4 > 'Z') {
throw new IllegalArgumentException("Invalid locale format: " + str);
}
if (len == 5) {
return new Locale(str.substring(0, 2), str.substring(3, 5));
} else {
if (str.charAt(5) != '_') {
throw new IllegalArgumentException("Invalid locale format: " + str);
}
return new Locale(str.substring(0, 2), str.substring(3, 5), str.substring(6));
}
}
}
//-----------------------------------------------------------------------
/**
* <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, never null
*/
public static List localeLookupList(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, never null
*/
public static List localeLookupList(Locale locale, Locale defaultLocale) {
List list = new ArrayList(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 availableLocaleList() {
return cAvailableLocaleList;
}
//-----------------------------------------------------------------------
/**
* <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 availableLocaleSet() {
Set set = cAvailableLocaleSet;
if (set == null) {
set = new HashSet(availableLocaleList());
set = Collections.unmodifiableSet(set);
cAvailableLocaleSet = set;
}
return 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(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, never null
*/
public static List languagesByCountry(String countryCode) {
List langs = (List) cLanguagesByCountry.get(countryCode); //syncd
if (langs == null) {
if (countryCode != null) {
langs = new ArrayList();
List locales = availableLocaleList();
for (int i = 0; i < locales.size(); i++) {
Locale locale = (Locale) locales.get(i);
if (countryCode.equals(locale.getCountry()) &&
locale.getVariant().length() == 0) {
langs.add(locale);
}
}
langs = Collections.unmodifiableList(langs);
} else {
langs = Collections.EMPTY_LIST;
}
cLanguagesByCountry.put(countryCode, langs); //syncd
}
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, never null
*/
public static List countriesByLanguage(String languageCode) {
List countries = (List) cCountriesByLanguage.get(languageCode); //syncd
if (countries == null) {
if (languageCode != null) {
countries = new ArrayList();
List locales = availableLocaleList();
for (int i = 0; i < locales.size(); i++) {
Locale locale = (Locale) locales.get(i);
if (languageCode.equals(locale.getLanguage()) &&
locale.getCountry().length() != 0 &&
locale.getVariant().length() == 0) {
countries.add(locale);
}
}
countries = Collections.unmodifiableList(countries);
} else {
countries = Collections.EMPTY_LIST;
}
cCountriesByLanguage.put(languageCode, countries); //syncd
}
return countries;
}
}
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