Java Locale lookup() Method

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Description

The Java Locale lookup(List<Locale.LanguageRange> priorityList, Collection<Locale> locales) method returns a Locale instance for the best-matching language tag using the lookup mechanism defined in RFC 4647.

Declaration

Following is the declaration for java.util.Locale.lookup() method

public static Locale lookup​(List<Locale.LanguageRange> priorityList, Collection<Locale> locales)

Parameters

priorityList − user's Language Priority List in which each language tag is sorted in descending order based on priority or weight.

locales − Locale instances used for matching.

Return Value

This method returns the best matching Locale instance chosen based on priority or weight, or null if nothing matches.

Exception

NullPointerException − if priorityList or locales is null

Getting Best Matched Language Tag Using Lookup on English, Japan Locales Example

The following example shows the usage of Java Locale lookup(List<Locale.LanguageRange>, Collection<Locale>) method. We're creating a string of comma separated locales and using that string, we've created a locale preference list. Now a list of locale is created and few locales are added. Using lookup() method, locales are searched and result is printed.

package com.tutorialspoint;

import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

public class LocaleDemo {
   public static void main(String[] args) {

      String tags = Locale.ENGLISH.toLanguageTag() 
         + ","
         + Locale.FRENCH.toLanguageTag();

      List<Locale.LanguageRange> priorityList = Locale.LanguageRange.parse(tags);
      List<Locale> localeList = new ArrayList<>();
      localeList.add(Locale.ENGLISH);
      localeList.add(Locale.JAPAN);

      Locale filteredTag = Locale.lookup(priorityList, localeList);

      System.out.println(filteredTag);
   }
}

Output

Let us compile and run the above program, this will produce the following result −

en

Getting Best Matched Language Tag Using Lookup on English, Canada, French Locales Example

The following example shows the usage of Java Locale lookup(List<Locale.LanguageRange>, Collection<Locale>) method. We're creating a different string of comma separated locales and using that string, we've created a locale preference list. Now a list of locale is created and few locales are added. Using lookup() method, locales are searched and result is printed.

package com.tutorialspoint;

import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

public class LocaleDemo {
   public static void main(String[] args) {

      String tags = Locale.ENGLISH.toLanguageTag() 
         + ","
         + Locale.FRENCH.toLanguageTag();

      List<Locale.LanguageRange> priorityList = Locale.LanguageRange.parse(tags);
      List<Locale> localeList = new ArrayList<>();
      localeList.add(Locale.ENGLISH);
      localeList.add(Locale.CANADA);
      localeList.add(Locale.FRENCH);

      Locale filteredTag = Locale.lookup(priorityList, localeList);

      System.out.println(filteredTag);
   }
}

Output

Let us compile and run the above program, this will produce the following result −

en

Getting Best Matched Language Tag Using Lookup on English, Japan Locales Example

The following example shows the usage of Java Locale lookup(List<Locale.LanguageRange>, Collection<Locale>,Locale.FilteringMode) method. We're creating a string of comma separated locales and using that string, we've created a locale preference list. Now a list of locale is created and few locales are added. Using lookup() method, locales are searched and result is printed.

package com.tutorialspoint;

import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

public class LocaleDemo {
   public static void main(String[] args) {

      String tags = Locale.ENGLISH.toLanguageTag() 
         + ","
         + Locale.CANADA.toLanguageTag();

      List<Locale.LanguageRange> priorityList = Locale.LanguageRange.parse(tags);
      List<Locale> localeList = new ArrayList<>();
      localeList.add(Locale.ENGLISH);
      localeList.add(Locale.JAPAN);

      Locale filteredTag = Locale.lookup(priorityList, localeList);

      System.out.println(filteredTag);
   }
}

Output

Let us compile and run the above program, this will produce the following result −

en