Java Locale lookupTag() Method

---

---

Description

The Java Locale lookupTag(List<Locale.LanguageRange> priorityList, Collection<String> tags) method returns the best-matching language tag using the lookup mechanism defined in RFC 4647. This lookup operation on the given tags ensures that the first matching tag with preserved case is returned.

Declaration

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

public static String lookupTag​(List<Locale.LanguageRange> priorityList, Collection<String> tags)

Parameters

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

tags − language tags.

Return Value

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

Exception

NullPointerException − if priorityList or locales is null

Getting Best Matched Language Tag for en, jp Locales Example

The following example shows the usage of Java Locale lookupTag() 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 lookupTag() 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<String> localeList = new ArrayList<>();
      localeList.add("en");
      localeList.add("jp");

      String filteredTags = Locale.lookupTag(priorityList, localeList);

      System.out.println(filteredTags);
   }
}

Output

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

en

Getting Best Matched Language Tag for en, en_CA, fr Locales Example

The following example shows the usage of Java Locale lookupTag() 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 lookupTag() 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<String> localeList = new ArrayList<>();
      localeList.add("en");
      localeList.add("en_CA");
      localeList.add("fr");

      String filteredTags = Locale.lookupTag(priorityList, localeList);

      System.out.println(filteredTags);
   }
}

Output

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

en

Getting Best Matched Language Tag for en, jp Locales Example

The following example shows the usage of Java Locale lookupTag() 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 lookupTag() 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<String> localeList = new ArrayList<>();
      localeList.add("en");
      localeList.add("jp");

      String filteredTags = Locale.lookupTag(priorityList, localeList);

      System.out.println(filteredTags);
   }
}

Output

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

en