LocaleUtils.java

  1. /*
  2.  * Licensed to the Apache Software Foundation (ASF) under one or more
  3.  * contributor license agreements.  See the NOTICE file distributed with
  4.  * this work for additional information regarding copyright ownership.
  5.  * The ASF licenses this file to You under the Apache License, Version 2.0
  6.  * (the "License"); you may not use this file except in compliance with
  7.  * the License.  You may obtain a copy of the License at
  8.  *
  9.  *      http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */
  17. package org.apache.commons.lang3;

  19. import java.util.ArrayList;
  20. import java.util.Arrays;
  21. import java.util.Collections;
  22. import java.util.HashSet;
  23. import java.util.List;
  24. import java.util.Locale;
  25. import java.util.Set;
  26. import java.util.concurrent.ConcurrentHashMap;
  27. import java.util.concurrent.ConcurrentMap;
  28. import java.util.function.Predicate;
  29. import java.util.stream.Collectors;

  31. /**
  32.  * Operations to assist when working with a {@link Locale}.
  33.  *
  34.  * <p>This class tries to handle {@code null} input gracefully.
  35.  * An exception will not be thrown for a {@code null} input.
  36.  * Each method documents its behavior in more detail.</p>
  37.  *
  38.  * @since 2.2
  39.  */
  40. public class LocaleUtils {

  42.     // class to avoid synchronization (Init on demand)
  43.     static class SyncAvoid {
  44.         /** Unmodifiable list of available locales. */
  45.         private static final List<Locale> AVAILABLE_LOCALE_LIST;
  46.         /** Unmodifiable set of available locales. */
  47.         private static final Set<Locale> AVAILABLE_LOCALE_SET;

  49.         static {
  50.             final List<Locale> list = new ArrayList<>(Arrays.asList(Locale.getAvailableLocales()));  // extra safe
  51.             AVAILABLE_LOCALE_LIST = Collections.unmodifiableList(list);
  52.             AVAILABLE_LOCALE_SET = Collections.unmodifiableSet(new HashSet<>(list));
  53.         }
  54.     }

  56.     /**
  57.      * The underscore character {@code '}{@value}{@code '}.
  58.      */
  59.     private static final char UNDERSCORE = '_';

  61.     /**
  62.      * The undetermined language {@value}.
  63.      */
  64.     private static final String UNDETERMINED = "und";

  66.     /**
  67.      * The dash character {@code '}{@value}{@code '}.
  68.      */
  69.     private static final char DASH = '-';

  71.     /**
  72.      * Concurrent map of language locales by country.
  73.      */
  74.     private static final ConcurrentMap<String, List<Locale>> cLanguagesByCountry = new ConcurrentHashMap<>();

  76.     /**
  77.      * Concurrent map of country locales by language.
  78.      */
  79.     private static final ConcurrentMap<String, List<Locale>> cCountriesByLanguage = new ConcurrentHashMap<>();

  81.     /**
  82.      * Obtains an unmodifiable list of installed locales.
  83.      *
  84.      * <p>This method is a wrapper around {@link Locale#getAvailableLocales()}.
  85.      * It is more efficient, as the JDK method must create a new array each
  86.      * time it is called.</p>
  87.      *
  88.      * @return the unmodifiable list of available locales
  89.      */
  90.     public static List<Locale> availableLocaleList() {
  91.         return SyncAvoid.AVAILABLE_LOCALE_LIST;
  92.     }

  94.     private static List<Locale> availableLocaleList(final Predicate<Locale> predicate) {
  95.         return availableLocaleList().stream().filter(predicate).collect(Collectors.toList());
  96.     }

  98.     /**
  99.      * Obtains an unmodifiable set of installed locales.
  100.      *
  101.      * <p>This method is a wrapper around {@link Locale#getAvailableLocales()}.
  102.      * It is more efficient, as the JDK method must create a new array each
  103.      * time it is called.</p>
  104.      *
  105.      * @return the unmodifiable set of available locales
  106.      */
  107.     public static Set<Locale> availableLocaleSet() {
  108.         return SyncAvoid.AVAILABLE_LOCALE_SET;
  109.     }

  111.     /**
  112.      * Obtains the list of countries supported for a given language.
  113.      *
  114.      * <p>This method takes a language code and searches to find the
  115.      * countries available for that language. Variant locales are removed.</p>
  116.      *
  117.      * @param languageCode  the 2 letter language code, null returns empty
  118.      * @return an unmodifiable List of Locale objects, not null
  119.      */
  120.     public static List<Locale> countriesByLanguage(final String languageCode) {
  121.         if (languageCode == null) {
  122.             return Collections.emptyList();
  123.         }
  124.         return cCountriesByLanguage.computeIfAbsent(languageCode, lc -> Collections.unmodifiableList(
  125.             availableLocaleList(locale -> languageCode.equals(locale.getLanguage()) && !locale.getCountry().isEmpty() && locale.getVariant().isEmpty())));
  126.     }

  128.     /**
  129.      * Checks if the locale specified is in the set of available locales.
  130.      *
  131.      * @param locale the Locale object to check if it is available
  132.      * @return true if the locale is a known locale
  133.      */
  134.     public static boolean isAvailableLocale(final Locale locale) {
  135.         return availableLocaleSet().contains(locale);
  136.     }

  138.     /**
  139.      * Checks whether the given String is a ISO 3166 alpha-2 country code.
  140.      *
  141.      * @param str the String to check
  142.      * @return true, is the given String is a ISO 3166 compliant country code.
  143.      */
  144.     private static boolean isISO3166CountryCode(final String str) {
  145.         return StringUtils.isAllUpperCase(str) && str.length() == 2;
  146.     }

  148.     /**
  149.      * Checks whether the given String is a ISO 639 compliant language code.
  150.      *
  151.      * @param str the String to check.
  152.      * @return true, if the given String is a ISO 639 compliant language code.
  153.      */
  154.     private static boolean isISO639LanguageCode(final String str) {
  155.         return StringUtils.isAllLowerCase(str) && (str.length() == 2 || str.length() == 3);
  156.     }

  158.     /**
  159.      * Tests whether a Locale's language is undetermined.
  160.      * <p>
  161.      * A Locale's language tag is undetermined if it's value is {@code "und"}. If a language is empty, or not well-formed (for example, "a" or"e2"), it will be
  162.      * equal to {@code "und"}.
  163.      * </p>
  164.      *
  165.      * @param locale the locale to test.
  166.      * @return whether a Locale's language is undetermined.
  167.      * @see Locale#toLanguageTag()
  168.      * @since 3.14.0
  169.      */
  170.     public static boolean isLanguageUndetermined(final Locale locale) {
  171.         return locale == null || UNDETERMINED.equals(locale.toLanguageTag());
  172.     }

  174.     /**
  175.      * Checks whether the given String is a UN M.49 numeric area code.
  176.      *
  177.      * @param str the String to check
  178.      * @return true, is the given String is a UN M.49 numeric area code.
  179.      */
  180.     private static boolean isNumericAreaCode(final String str) {
  181.         return StringUtils.isNumeric(str) && str.length() == 3;
  182.     }

  184.     /**
  185.      * Obtains the list of languages supported for a given country.
  186.      *
  187.      * <p>This method takes a country code and searches to find the
  188.      * languages available for that country. Variant locales are removed.</p>
  189.      *
  190.      * @param countryCode  the 2-letter country code, null returns empty
  191.      * @return an unmodifiable List of Locale objects, not null
  192.      */
  193.     public static List<Locale> languagesByCountry(final String countryCode) {
  194.         if (countryCode == null) {
  195.             return Collections.emptyList();
  196.         }
  197.         return cLanguagesByCountry.computeIfAbsent(countryCode,
  198.             k -> Collections.unmodifiableList(availableLocaleList(locale -> countryCode.equals(locale.getCountry()) && locale.getVariant().isEmpty())));
  199.     }

  201.     /**
  202.      * Obtains the list of locales to search through when performing
  203.      * a locale search.
  204.      *
  205.      * <pre>
  206.      * localeLookupList(Locale("fr", "CA", "xxx"))
  207.      *   = [Locale("fr", "CA", "xxx"), Locale("fr", "CA"), Locale("fr")]
  208.      * </pre>
  209.      *
  210.      * @param locale  the locale to start from
  211.      * @return the unmodifiable list of Locale objects, 0 being locale, not null
  212.      */
  213.     public static List<Locale> localeLookupList(final Locale locale) {
  214.         return localeLookupList(locale, locale);
  215.     }

  217.     /**
  218.      * Obtains the list of locales to search through when performing
  219.      * a locale search.
  220.      *
  221.      * <pre>
  222.      * localeLookupList(Locale("fr", "CA", "xxx"), Locale("en"))
  223.      *   = [Locale("fr", "CA", "xxx"), Locale("fr", "CA"), Locale("fr"), Locale("en"]
  224.      * </pre>
  225.      *
  226.      * <p>The result list begins with the most specific locale, then the
  227.      * next more general and so on, finishing with the default locale.
  228.      * The list will never contain the same locale twice.</p>
  229.      *
  230.      * @param locale  the locale to start from, null returns empty list
  231.      * @param defaultLocale  the default locale to use if no other is found
  232.      * @return the unmodifiable list of Locale objects, 0 being locale, not null
  233.      */
  234.     public static List<Locale> localeLookupList(final Locale locale, final Locale defaultLocale) {
  235.         final List<Locale> list = new ArrayList<>(4);
  236.         if (locale != null) {
  237.             list.add(locale);
  238.             if (!locale.getVariant().isEmpty()) {
  239.                 list.add(new Locale(locale.getLanguage(), locale.getCountry()));
  240.             }
  241.             if (!locale.getCountry().isEmpty()) {
  242.                 list.add(new Locale(locale.getLanguage(), StringUtils.EMPTY));
  243.             }
  244.             if (!list.contains(defaultLocale)) {
  245.                 list.add(defaultLocale);
  246.             }
  247.         }
  248.         return Collections.unmodifiableList(list);
  249.     }

  251.     /**
  252.      * Tries to parse a Locale from the given String.
  253.      * <p>
  254.      * See {@Link Locale} for the format.
  255.      * </p>
  256.      *
  257.      * @param str the String to parse as a Locale.
  258.      * @return a Locale parsed from the given String.
  259.      * @throws IllegalArgumentException if the given String can not be parsed.
  260.      * @see Locale
  261.      */
  262.     private static Locale parseLocale(final String str) {
  263.         if (isISO639LanguageCode(str)) {
  264.             return new Locale(str);
  265.         }
  266.         final int limit = 3;
  267.         final char separator = str.indexOf(UNDERSCORE) != -1 ? UNDERSCORE : DASH;
  268.         final String[] segments = str.split(String.valueOf(separator), 3);
  269.         final String language = segments[0];
  270.         if (segments.length == 2) {
  271.             final String country = segments[1];
  272.             if (isISO639LanguageCode(language) && isISO3166CountryCode(country) || isNumericAreaCode(country)) {
  273.                 return new Locale(language, country);
  274.             }
  275.         } else if (segments.length == limit) {
  276.             final String country = segments[1];
  277.             final String variant = segments[2];
  278.             if (isISO639LanguageCode(language) &&
  279.                     (country.isEmpty() || isISO3166CountryCode(country) || isNumericAreaCode(country)) &&
  280.                     !variant.isEmpty()) {
  281.                 return new Locale(language, country, variant);
  282.             }
  283.         }
  284.         throw new IllegalArgumentException("Invalid locale format: " + str);
  285.     }

  287.     /**
  288.      * Returns the given locale if non-{@code null}, otherwise {@link Locale#getDefault()}.
  289.      *
  290.      * @param locale a locale or {@code null}.
  291.      * @return the given locale if non-{@code null}, otherwise {@link Locale#getDefault()}.
  292.      * @since 3.12.0
  293.      */
  294.     public static Locale toLocale(final Locale locale) {
  295.         return locale != null ? locale : Locale.getDefault();
  296.     }

  298.     /**
  299.      * Converts a String to a Locale.
  300.      *
  301.      * <p>This method takes the string format of a locale and creates the
  302.      * locale object from it.</p>
  303.      *
  304.      * <pre>
  305.      *   LocaleUtils.toLocale("")           = new Locale("", "")
  306.      *   LocaleUtils.toLocale("en")         = new Locale("en", "")
  307.      *   LocaleUtils.toLocale("en_GB")      = new Locale("en", "GB")
  308.      *   LocaleUtils.toLocale("en-GB")      = new Locale("en", "GB")
  309.      *   LocaleUtils.toLocale("en_001")     = new Locale("en", "001")
  310.      *   LocaleUtils.toLocale("en_GB_xxx")  = new Locale("en", "GB", "xxx")   (#)
  311.      * </pre>
  312.      *
  313.      * <p>(#) The behavior of the JDK variant constructor changed between JDK1.3 and JDK1.4.
  314.      * In JDK1.3, the constructor upper cases the variant, in JDK1.4, it doesn't.
  315.      * Thus, the result from getVariant() may vary depending on your JDK.</p>
  316.      *
  317.      * <p>This method validates the input strictly.
  318.      * The language code must be lowercase.
  319.      * The country code must be uppercase.
  320.      * The separator must be an underscore or a dash.
  321.      * The length must be correct.
  322.      * </p>
  323.      *
  324.      * @param str  the locale String to convert, null returns null
  325.      * @return a Locale, null if null input
  326.      * @throws IllegalArgumentException if the string is an invalid format
  327.      * @see Locale#forLanguageTag(String)
  328.      */
  329.     public static Locale toLocale(final String str) {
  330.         if (str == null) {
  331.             // TODO Should this return the default locale?
  332.             return null;
  333.         }
  334.         if (str.isEmpty()) { // LANG-941 - JDK 8 introduced an empty locale where all fields are blank
  335.             return new Locale(StringUtils.EMPTY, StringUtils.EMPTY);
  336.         }
  337.         if (str.contains("#")) { // LANG-879 - Cannot handle Java 7 script & extensions
  338.             throw new IllegalArgumentException("Invalid locale format: " + str);
  339.         }
  340.         final int len = str.length();
  341.         if (len < 2) {
  342.             throw new IllegalArgumentException("Invalid locale format: " + str);
  343.         }
  344.         final char ch0 = str.charAt(0);
  345.         if (ch0 == UNDERSCORE || ch0 == DASH) {
  346.             if (len < 3) {
  347.                 throw new IllegalArgumentException("Invalid locale format: " + str);
  348.             }
  349.             final char ch1 = str.charAt(1);
  350.             final char ch2 = str.charAt(2);
  351.             if (!Character.isUpperCase(ch1) || !Character.isUpperCase(ch2)) {
  352.                 throw new IllegalArgumentException("Invalid locale format: " + str);
  353.             }
  354.             if (len == 3) {
  355.                 return new Locale(StringUtils.EMPTY, str.substring(1, 3));
  356.             }
  357.             if (len < 5) {
  358.                 throw new IllegalArgumentException("Invalid locale format: " + str);
  359.             }
  360.             if (str.charAt(3) != ch0) {
  361.                 throw new IllegalArgumentException("Invalid locale format: " + str);
  362.             }
  363.             return new Locale(StringUtils.EMPTY, str.substring(1, 3), str.substring(4));
  364.         }

  366.         return parseLocale(str);
  367.     }

  369.     /**
  370.      * {@link LocaleUtils} instances should NOT be constructed in standard programming.
  371.      * Instead, the class should be used as {@code LocaleUtils.toLocale("en_GB");}.
  372.      *
  373.      * <p>This constructor is public to permit tools that require a JavaBean instance
  374.      * to operate.</p>
  375.      *
  376.      * @deprecated TODO Make private in 4.0.
  377.      */
  378.     @Deprecated
  379.     public LocaleUtils() {
  380.         // empty
  381.     }

  383. }
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