Localization. Practical Tasks

You saved title=Bücher in a UTF-8 file messages_de.properties, ran the program on Java 8, and the console shows “Bücher” instead of “Bücher”. Before Java 9, ResourceBundle read properties files as ISO-8859-1, so any non-ASCII text saved in UTF-8 turned into garbage. Since Java 9 (JEP 226) such files are read as UTF-8 by default, but this is only one of the surprises you meet the first time you localize an application.

This page collects 3 Java localization exercises with hints: properties files with texts in two languages, a report whose title changes with the locale, and prices in the currency of the current locale for the online store practice project. You will need the classes Locale, ResourceBundle and NumberFormat; the general theory is in the lesson Internationalization (i18n) and Localization (l10n) in Java.

Java Topics in Two Languages (ResourceBundle)

1. Create properties files in two languages, for example English and French, containing the names of the Java topics you have studied.
2. Write a method that takes a locale as a parameter and prints all the information from the properties file.

FullReport Class: a Report Titled in the Locale Language

Employee Report · part 2 of 2 · ← part 1

1. Create a FullReport class that prints the same information as the Report class (Employee Salary Report on the Java String Exercises page), but the report title must change depending on the selected locale (use the ResourceBundle class).
2. Use the NumberFormat class to format the numbers.

Receipt with Prices in the Current Locale Currency

Online Store · part 4 of 4 · ← part 3

1. When a customer makes a purchase, print a report of the purchased products to the console. The currency must match the current locale (use the NumberFormat class). For example, for the locale en_US:

   Product        Price
   --------------------
   Jeans      $1,500.78
   Skirt      $1,000.56
   Tie          $500.78
   --------------------
   Total:     $3,002.12
   

2. The report must be in the language of the current locale — use ResourceBundle.

Solution on Patreon →

Common Localization Mistakes and How to Fix Them

In localization exercises the program usually breaks not because of the logic but because of the environment: a properties file is not on the classpath, a key is missing from one of the files, or a formatted amount contains a non-breaking space instead of a regular one. The table lists the symptom, the cause and the fix.

What Does This Code Print: the Fallback Locale

If there is no properties file for the requested locale, ResourceBundle.getBundle() first looks for the file of the default locale (Locale.getDefault()) and only then falls back to the base file without a suffix. That is why, on a computer with a French default locale, a “German” report is unexpectedly printed in French rather than in the language of the base file (search order).

// src/main/resources/messages.properties:    title=Report
// src/main/resources/messages_fr.properties: title=Rapport
Locale.setDefault(Locale.of("fr", "FR"));   // before Java 19: new Locale("fr", "FR")

ResourceBundle bundle = ResourceBundle.getBundle("messages", Locale.GERMANY);
System.out.println(bundle.getString("title"));
System.out.println(bundle.getLocale());
// Output:
// Rapport
// fr

There is no messages_de_DE.properties file, so the search moves on to the default locale fr_FR and finds messages_fr.properties. To always get the base file when a translation is missing, switch this step off with ResourceBundle.Control:

ResourceBundle bundle = ResourceBundle.getBundle("messages", Locale.GERMANY,
        ResourceBundle.Control.getNoFallbackControl(ResourceBundle.Control.FORMAT_DEFAULT));
System.out.println(bundle.getString("title"));
System.out.println(bundle.getLocale().equals(Locale.ROOT));
// Output:
// Report
// true

The Control variant works in a regular (non-modular) project; calling it from a named module on Java 9+ throws UnsupportedOperationException.