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With inspiration from other libraries
/*
* 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;
/**
* Operations to assist when working with a {@link Locale}.
*
* 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.
*
* @since 2.2
*/
public class LocaleUtils {
/** Concurrent map of language locales by country. */
private static final ConcurrentMap> cLanguagesByCountry =
new ConcurrentHashMap<>();
/** Concurrent map of country locales by language. */
private static final ConcurrentMap> cCountriesByLanguage =
new ConcurrentHashMap<>();
/**
* {@code LocaleUtils} instances should NOT be constructed in standard programming.
* Instead, the class should be used as {@code LocaleUtils.toLocale("en_GB");}.
*
* This constructor is public to permit tools that require a JavaBean instance
* to operate.
*/
public LocaleUtils() {
super();
}
//-----------------------------------------------------------------------
/**
* Converts a String to a Locale.
*
* This method takes the string format of a locale and creates the
* locale object from it.
*
*
* LocaleUtils.toLocale("") = new Locale("", "")
* LocaleUtils.toLocale("en") = new Locale("en", "")
* LocaleUtils.toLocale("en_GB") = new Locale("en", "GB")
* LocaleUtils.toLocale("en_001") = new Locale("en", "001")
* LocaleUtils.toLocale("en_GB_xxx") = new Locale("en", "GB", "xxx") (#)
*
*
* (#) 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.
*
* 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.
*
*
* @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(StringUtils.EMPTY, StringUtils.EMPTY);
}
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(StringUtils.EMPTY, 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(StringUtils.EMPTY, str.substring(1, 3), str.substring(4));
}
return parseLocale(str);
}
/**
* Tries to parse a locale from the given String.
*
* @param str the String to parse a locale from.
* @return a Locale instance parsed from the given String.
* @throws IllegalArgumentException if the given String can not be parsed.
*/
private static Locale parseLocale(final String str) {
if (isISO639LanguageCode(str)) {
return new Locale(str);
}
final String[] segments = str.split("_", -1);
final String language = segments[0];
if (segments.length == 2) {
final String country = segments[1];
if (isISO639LanguageCode(language) && isISO3166CountryCode(country) ||
isNumericAreaCode(country)) {
return new Locale(language, country);
}
} else if (segments.length == 3) {
final String country = segments[1];
final String variant = segments[2];
if (isISO639LanguageCode(language) &&
(country.isEmpty() || isISO3166CountryCode(country) || isNumericAreaCode(country)) &&
!variant.isEmpty()) {
return new Locale(language, country, variant);
}
}
throw new IllegalArgumentException("Invalid locale format: " + str);
}
/**
* Checks whether the given String is a ISO 639 compliant language code.
*
* @param str the String to check.
* @return true, if the given String is a ISO 639 compliant language code.
*/
private static boolean isISO639LanguageCode(final String str) {
return StringUtils.isAllLowerCase(str) && (str.length() == 2 || str.length() == 3);
}
/**
* Checks whether the given String is a ISO 3166 alpha-2 country code.
*
* @param str the String to check
* @return true, is the given String is a ISO 3166 compliant country code.
*/
private static boolean isISO3166CountryCode(final String str) {
return StringUtils.isAllUpperCase(str) && str.length() == 2;
}
/**
* Checks whether the given String is a UN M.49 numeric area code.
*
* @param str the String to check
* @return true, is the given String is a UN M.49 numeric area code.
*/
private static boolean isNumericAreaCode(final String str) {
return StringUtils.isNumeric(str) && str.length() == 3;
}
//-----------------------------------------------------------------------
/**
* Obtains the list of locales to search through when performing
* a locale search.
*
*
* localeLookupList(Locale("fr","CA","xxx"))
* = [Locale("fr","CA","xxx"), Locale("fr","CA"), Locale("fr")]
*
*
* @param locale the locale to start from
* @return the unmodifiable list of Locale objects, 0 being locale, not null
*/
public static List localeLookupList(final Locale locale) {
return localeLookupList(locale, locale);
}
//-----------------------------------------------------------------------
/**
* Obtains the list of locales to search through when performing
* a locale search.
*
*
* localeLookupList(Locale("fr", "CA", "xxx"), Locale("en"))
* = [Locale("fr","CA","xxx"), Locale("fr","CA"), Locale("fr"), Locale("en"]
*
*
* 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.
*
* @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 localeLookupList(final Locale locale, final Locale defaultLocale) {
final List list = new ArrayList<>(4);
if (locale != null) {
list.add(locale);
if (!locale.getVariant().isEmpty()) {
list.add(new Locale(locale.getLanguage(), locale.getCountry()));
}
if (!locale.getCountry().isEmpty()) {
list.add(new Locale(locale.getLanguage(), StringUtils.EMPTY));
}
if (!list.contains(defaultLocale)) {
list.add(defaultLocale);
}
}
return Collections.unmodifiableList(list);
}
//-----------------------------------------------------------------------
/**
* Obtains an unmodifiable list of installed locales.
*
* 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.
*
* @return the unmodifiable list of available locales
*/
public static List availableLocaleList() {
return SyncAvoid.AVAILABLE_LOCALE_LIST;
}
//-----------------------------------------------------------------------
/**
* Obtains an unmodifiable set of installed locales.
*
* 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.
*
* @return the unmodifiable set of available locales
*/
public static Set availableLocaleSet() {
return SyncAvoid.AVAILABLE_LOCALE_SET;
}
//-----------------------------------------------------------------------
/**
* Checks if the locale specified is in the list of available locales.
*
* @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);
}
//-----------------------------------------------------------------------
/**
* Obtains the list of languages supported for a given country.
*
* This method takes a country code and searches to find the
* languages available for that country. Variant locales are removed.
*
* @param countryCode the 2 letter country code, null returns empty
* @return an unmodifiable List of Locale objects, not null
*/
public static List languagesByCountry(final String countryCode) {
if (countryCode == null) {
return Collections.emptyList();
}
List langs = cLanguagesByCountry.get(countryCode);
if (langs == null) {
langs = new ArrayList<>();
final List locales = availableLocaleList();
for (final Locale locale : locales) {
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;
}
//-----------------------------------------------------------------------
/**
* Obtains the list of countries supported for a given language.
*
* This method takes a language code and searches to find the
* countries available for that language. Variant locales are removed.
*
* @param languageCode the 2 letter language code, null returns empty
* @return an unmodifiable List of Locale objects, not null
*/
public static List countriesByLanguage(final String languageCode) {
if (languageCode == null) {
return Collections.emptyList();
}
List countries = cCountriesByLanguage.get(languageCode);
if (countries == null) {
countries = new ArrayList<>();
final List locales = availableLocaleList();
for (final Locale locale : locales) {
if (languageCode.equals(locale.getLanguage()) &&
!locale.getCountry().isEmpty() &&
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 AVAILABLE_LOCALE_LIST;
/** Unmodifiable set of available locales. */
private static final Set AVAILABLE_LOCALE_SET;
static {
final List list = new ArrayList<>(Arrays.asList(Locale.getAvailableLocales())); // extra safe
AVAILABLE_LOCALE_LIST = Collections.unmodifiableList(list);
AVAILABLE_LOCALE_SET = Collections.unmodifiableSet(new HashSet<>(list));
}
}
}