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Java in a Nutshell

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11. Internationalization

Internationalization is the process of making a program flexible enough to run correctly in any locale, as discussed in Chapter 4, What's New in Java 1.1. The required corollary to internationalization is localization--the process of arranging for a program to run in a specific locale.

There are several distinct steps to the task of internationalization. Java 1.1 addresses these steps with several different mechanisms:

  • A program must be able to read, write, and manipulate localized text. Java uses the Unicode character encoding, which by itself is a huge step towards internationalization. In addition, in Java 1.1 the InputStreamReader and OutputStreamWriter classes convert text from a locale-specific encoding to Unicode and from Unicode to a locale-specific encoding, respectively.

  • A program must conform to local customs when displaying dates and times, formatting numbers, and sorting strings. Java addresses these issues with the classes in the new java.text package.

  • A program must display all user-visible text in the local language. Translating the messages a program displays is always one of the main tasks in localizing a program. A more important task is writing the program so that all user-visible text is fetched at runtime, rather than hard-coded directly into the program. Java 1.1 facilitates this process with the ResourceBundle class and its subclasses in the java.util package.

This chapter discusses all three of these aspects of internationalization.

11.1 A Word About Locales

A locale represents a geographic, political, or cultural region. In Java 1.1, locales are represented by the java.util.Locale class. A locale is frequently defined by a language, which is represented by its standard lowercase two-letter code, such as en (English) or fr (French). Sometimes, however, language alone is not sufficient to uniquely specify a locale, and a country is added to the specification. A country is represented by an uppercase two-letter code. For example, the United States English locale (en_US) is distinct from the British English locale (en_GB), and the French spoken in Canada (fr_CA) is different from the French spoken in France (fr_FR). Occasionally, the scope of a locale is further narrowed with the addition of a system-dependent "variant" string.

The Locale class maintains a static default locale, which can be set and queried with Locale.setDefault() and Locale.getDefault(). Locale-sensitive methods in Java 1.1 typically come in two forms. One uses the default locale and the other uses a Locale object that is explicitly specified as an argument. A program can create and use any number of non-default Locale objects, although it is more common simply to rely on the default locale, which is inherited from the underlying default locale on the native platform. Locale-sensitive classes in Java often provide a method to query the list of locales that they support.

Finally, note that AWT components in Java 1.1 have a locale property, so it is possible for different components to use different locales. (Most components, however, are not locale-sensitive; they behave the same in any locale.)

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