Locale Class in Java

A Locale object represents a specific language, country or region, such as "English in the United States" or "Hindi in India". It doesn't hold any text or formats itself. It is an identifier that you pass to other classes, such as NumberFormat, DateTimeFormatter and ResourceBundle, so they know which rules and translations to use. The class is java.util.Locale, and its objects are immutable. In this lesson, you will learn the parts of a locale, the ways to create one, how to read its names, and how the default locale works.

The Parts of a Locale

Written together as a language tag, they look like en-US, hi-IN or fr-CA.

Ways to Create a Locale

Constants come in two kinds: a language alone, such as Locale.GERMAN (de), and a language with a country, such as Locale.GERMANY (de-DE).

Methods

Example: Creating and Reading Locales

import java.util.Locale;
 
public class Locales {
    public static void main(String[] args) {
        Locale india = Locale.of("hi", "IN");
        System.out.println(india + " | " + india.toLanguageTag());
        System.out.println("language: " + india.getLanguage()
            + " -> " + india.getDisplayLanguage(Locale.ENGLISH));
        System.out.println("country:  " + india.getCountry()
            + " -> " + india.getDisplayCountry(Locale.ENGLISH));
        System.out.println("name in English: "
            + india.getDisplayName(Locale.ENGLISH));
        System.out.println("name in German:  "
            + india.getDisplayName(Locale.GERMAN));
        System.out.println("name in Hindi:   "
            + india.getDisplayName(india));
 
        Locale fromTag = Locale.forLanguageTag("fr-CA");
        System.out.println(fromTag.getDisplayName(Locale.ENGLISH));
 
        Locale built = new Locale.Builder()
            .setLanguage("te").setRegion("IN").build();
        System.out.println(built.toLanguageTag() + " = "
            + built.getDisplayName(Locale.ENGLISH));
 
        System.out.println(Locale.GERMANY.equals(Locale.of("de", "DE")));
        System.out.println(Locale.GERMAN + " vs " + Locale.GERMANY);
 
        // Rules that depend on the language.
        System.out.println("TITLE".toLowerCase(Locale.ROOT)
            + " / " + "TITLE".toLowerCase(Locale.of("tr", "TR")));
 
        System.out.println("Installed locales: more than 100? "
            + (Locale.getAvailableLocales().length > 100));
    }
}

hi_IN | hi-IN
language: hi -> Hindi
country:  IN -> India
name in English: Hindi (India)
name in German:  Hindi (Indien)
name in Hindi:   हिन्दी (भारत)
French (Canada)
te-IN = Telugu (India)
true
de vs de_DE
title / tıtle
Installed locales: more than 100? true

Explanation:

• toString() gives hi_IN with an underscore, the older form. toLanguageTag() gives hi-IN, the standard form to store and exchange.
• Display names can be requested in any language: "Hindi (India)" in English, "Hindi (Indien)" in German, and in Hindi itself.
• forLanguageTag and the builder create the same kind of object from different inputs.
• Equality: two locales with the same parts are equal.
• Locale.GERMAN vs Locale.GERMANY: de is the language anywhere; de_DE is German as used in Germany. They can differ in formats: Germany and Switzerland write numbers differently.
• Case rules depend on the language. In Turkish, the lowercase of I is the dotless ı, so "TITLE".toLowerCase(turkish) gives tıtle. For text that isn't for people, such as keys, file names and protocol words, use Locale.ROOT, the neutral locale.

The Default Locale

Every JVM has a default locale, taken from the operating system's settings at startup. Methods that don't receive a locale use it: String.format("%,d", n), NumberFormat.getInstance(), toLowerCase().

Common Mistakes

Using new Locale(...). It is deprecated; use Locale.of.

Confusing language with country. Locale.FRENCH and Locale.FRANCE are different, and so are en-US and en-GB.

Calling toLowerCase() or toUpperCase() without a locale on identifiers. On a Turkish system, "ID".toLowerCase() isn't "id". Use Locale.ROOT.

Storing toString() and reading it back with forLanguageTag. hi_IN isn't a valid tag; store toLanguageTag().

Interview Corner

Practice

1. Easy: Print the display name of Locale.JAPAN in English, in French and in Japanese.
2. Harder: Print every available locale whose country is IN, with its language tag and English display name, sorted by tag.

Key Takeaways