Java.Core.What is “internationalization”, “localization” in Java ?

Internationalization (i18n) & Localization (l10n) in Java

Internationalization (i18n) and Localization (l10n) in Java are used to develop applications that support multiple languages, regions, and cultural formats without changing the core code.

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1. What is Internationalization (i18n)?

✅ Internationalization (i18n) is the process of designing an application so that it can be easily adapted to different languages and regions without modifying the codebase.

🔹 Key Features of i18n:

• Separates code from language-specific data.
• Uses resource bundles to store language-specific messages.
• Supports date, time, number, and currency formatting.

✅ Example of Internationalization:

import java.util.*;

public class InternationalizationExample {
    public static void main(String[] args) {
        ResourceBundle bundle = ResourceBundle.getBundle("Messages", Locale.FRANCE);
        System.out.println(bundle.getString("greeting"));
    }
}

ResourceBundle.getBundle("Messages", Locale.FRANCE) → Loads French translations.

2. What is Localization (l10n)?

✅ Localization (l10n) is the process of translating and adapting an internationalized application for a specific language or region.

🔹 Key Features of l10n:

• Provides translated text in different languages.
• Customizes date, number, and currency formats.
• Adapts regional settings (e.g., decimal separator in 1,000.50 vs. 1.000,50).

✅ Example: Resource Bundle for English (Messages_en.properties)

greeting=Hello, welcome to our application!

✅ Example: Resource Bundle for French (Messages_fr.properties)

greeting=Bonjour, bienvenue dans notre application !

✅ Example: Switching Language at Runtime

import java.util.*;

public class LocalizationExample {
    public static void main(String[] args) {
        Locale locale = new Locale("fr", "FR"); // Change to French
        ResourceBundle bundle = ResourceBundle.getBundle("Messages", locale);
        System.out.println(bundle.getString("greeting")); // Output: Bonjour, bienvenue...
    }
}

🔹 Key Takeaway: The same application displays messages in different languages based on the Locale.

3. Difference Between Internationalization & Localization

Feature	Internationalization (i18n)	Localization (l10n)
Definition	Designing software to support multiple languages	Translating & adapting the application for a specific language
Goal	Make code language-independent	Provide region-specific content
Who Does It?	Developers	Translators/Localizers
Example	Using ResourceBundle to separate text	Creating Messages_fr.properties for French

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4. Formatting Numbers, Dates, and Currency Based on Locale

Java provides the NumberFormat and DateFormat classes to format data based on regional settings.

✅ Example: Formatting Currency Based on Locale

import java.text.NumberFormat;
import java.util.Locale;

public class CurrencyLocalization {
    public static void main(String[] args) {
        double amount = 1234.56;

        NumberFormat usFormat = NumberFormat.getCurrencyInstance(Locale.US);
        NumberFormat frFormat = NumberFormat.getCurrencyInstance(Locale.FRANCE);

        System.out.println("US: " + usFormat.format(amount)); // Output: $1,234.56
        System.out.println("France: " + frFormat.format(amount)); // Output: 1 234,56 €
    }
}

✅ Example: Formatting Dates Based on Locale

import java.text.DateFormat;
import java.util.*;

public class DateLocalization {
    public static void main(String[] args) {
        Date today = new Date();

        DateFormat usFormat = DateFormat.getDateInstance(DateFormat.LONG, Locale.US);
        DateFormat frFormat = DateFormat.getDateInstance(DateFormat.LONG, Locale.FRANCE);

        System.out.println("US: " + usFormat.format(today)); // Output: January 12, 2025
        System.out.println("France: " + frFormat.format(today)); // Output: 12 janvier 2025
    }
}

🔹 Key Takeaway: The same number and date are formatted differently based on the locale.

5. Summary

Feature	Internationalization (i18n)	Localization (l10n)
Purpose	Make the application language-independent	Adapt the application for a specific language
Process	Use ResourceBundle, Locale, NumberFormat, DateFormat	Create translated properties files
Who Does It?	Developers	Translators
Example	ResourceBundle.getBundle("Messages", locale)	Messages_fr.properties for French

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Final Thoughts

✔ Internationalization makes code flexible, and localization makes it usable worldwide.
✔ ResourceBundle + Locale = Easy text translation.
✔ NumberFormat, DateFormat, CurrencyFormat = Region-based formatting.