JDK 18国际化指南：Java SE 18国际化技术详解

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本资源是一份名为《Java Platform, Standard Edition Internationalization Guide》的文档，版本为Release 18，编号为F51165-01，发布日期为2022年3月。这份指南是Oracle及其关联公司于1993年和2022年共同发布的，旨在为Java平台提供国际化的详细指导。作为标准版的一部分，它关注的是如何在Java应用程序中实现国际化和本地化，以确保跨语言环境下的正确运行和用户体验。在JDK 18的国际ization (i18n) 指南中，主要包含了以下几个关键知识点： 1. **国际化基础**：文档首先介绍了国际化的概念，即软件设计时考虑到全球用户的需求，支持多种语言和文化特性。这包括文本显示、日期时间格式、货币符号等的处理方式。 2. **资源管理**：如何有效地管理和组织国际化资源，如文本字符串、图像和布局信息，以便在不同的语言环境下进行替换和加载。 3. **字符集与编码**：讲解了Java中的字符集支持，如Unicode、UTF-8等，以及如何处理不同字符集之间的转换和兼容性问题。 4. **本地化API**：介绍Java提供的Localizations API，如java.text.MessageFormat、java.util.Locale和java.util.ResourceBundle，这些工具帮助开发者创建和维护本地化的应用程序资源。 5. **日期和时间格式化**：讨论了如何根据用户的本地设置正确地格式化日期和时间，包括时区处理。 6. **数字和货币格式**：指导如何适应不同国家和地区的数字和货币格式规范，如千位分隔符、小数点位置等。 7. **键盘输入和显示**：针对各种语言的键盘布局和输入法，提供支持策略。 8. **国际化测试**：强调了在开发过程中对国际化特性的测试，确保跨语言环境的稳定性。 9. **版权与许可**：文档开头的法律声明强调了软件使用和分发的限制，以及未经许可的复制、修改或公开展示的禁止，特别是对于美国政府用户和代理购买的情况。这份指南是开发人员在构建具有国际友好性的Java应用时的重要参考资料，有助于确保产品在全球市场上的可访问性和可用性。阅读并遵循其中的指导，可以帮助开发者避免常见的国际化错误，提升用户体验。

Internationalization Overview

Internationalization is the process of designing an application so that it can be adapted to

various languages and regions without engineering changes. Sometimes the term

internationalization is abbreviated as i18n, because there are 18 letters between the first "i"

and the last "n."

An internationalized program has the following characteristics:

• With the addition of localization data, the same executable can run worldwide.

• Textual elements, such as status messages and the GUI component labels, are not

hardcoded in the program. Instead they are stored outside the source code and retrieved

dynamically.

• Support for new languages does not require recompilation.

• Culturally-dependent data, such as dates and currencies, appear in formats that conform

to the end user's region and language.

• It can be localized quickly.

The internet demands global software - that is, software that can be developed independently

of the countries or languages of its users, and then localized for multiple countries or regions.

The Java Platform provides a rich set of APIs for developing global applications. These

internationalization APIs are based on the Unicode standard and include the ability to adapt

text, numbers, dates, currency, and user-defined objects to any country's conventions.

This guide summarizes the internationalization APIs and features of the Java Platform,

Standard Edition. For coding examples and step-by-step instructions, see the

Internationalization Trail in the Java Tutorials.

Text Representation

The Java programming language is based on the Unicode character set, and several libraries

implement the Unicode standard. Unicode is an international character set standard which

supports all of the major scripts of the world, as well as common technical symbols. The

original Unicode specification defined characters as fixed-width 16-bit entities, but the

Unicode standard has since been changed to allow for characters whose representation

requires more than 16 bits. The range of legal code points is now U+0000 to U+10FFFF. An

encoding defined by the standard, UTF-16, allows to represent all Unicode code points using

one or two 16-bit units.

The primitive data type char in the Java programming language is an unsigned 16-bit integer

that can represent a Unicode code point in the range U+0000 to U+FFFF, or the code units of

UTF-16. The various types and classes in the Java platform that represent character

sequences - char[], implementations of java.lang.CharSequence (such as the String

class), and implementations of java.text.CharacterIterator - are UTF-16 sequences.

Most Java source code is written in ASCII, a 7-bit character encoding, or ISO-8859-1, an 8-bit

character encoding, but is translated into UTF-16 before processing.

The Character class is an object wrapper for the char primitive type. The Character

class also contains static methods such as isLowerCase() and isDigit() for

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determining the properties of a character. These methods have overloads that accept

either a char (which allows representation of Unicode code points in the range U+0000

to U+FFFF) or an int (which allows representation of all Unicode code points).

Locale Identification and Localization

A Locale object is an identifier for a particular combination of language and region.

Localization is the process of adapting software for a specific region or language by

adding locale-specific components and translating text.

Locales

On the Java platform, a locale is simply an identifier for a particular combination of

language and region. It is not a collection of locale-specific attributes. Instead, each

locale-sensitive class maintains its own locale-specific information. With this design,

there is no difference in how user and system objects maintain their locale-specific

resources. Both use the standard localization mechanism.

Java programs are not assigned a single global locale. All locale-sensitive operations

may be explicitly given a locale as an argument. This greatly simplifies multilingual

programs. While a global locale is not enforced, a default locale is available for

programs that do not wish to manage locales explicitly. A default locale also makes it

possible to affect the behavior of the entire presentation with a single choice.

Java locales act as requests for certain behavior from another object. For example, a

French Canadian locale passed to a Calendar object asks that the Calendar

behave correctly for the customs of Quebec. It is up to the object accepting the locale

to do the right thing. If the object has not been localized for a particular locale, it will try

to find a "close" match with a locale for which it has been localized. Thus if a

Calendar object was not localized for French Canada, but was localized for the

French language in general, it would use the French localization instead.

Locale Class

A Locale object represents a specific geographical, political, or cultural region. An

operation that requires a locale to perform its task is called locale-sensitive and uses

the

Locale

object to tailor information for the user. For example, displaying a number is

a locale-sensitive operation - the number should be formatted according to the

customs and conventions of the user's native country, region, or culture.

Supported Locales

On the Java platform, there does not have to be a single set of supported locales,

since each class maintains its own localizations. Nevertheless, there is a consistent

set of localizations supported by the classes of the Java Platform. Other

implementations of the Java Platform may support different locales. Locales that are

supported by the JDK are summarized by release. Use the search field on the

Technical Resources from Oracle page and search for "Supported Locales" to see

what is supported.

Chapter 1

Locale Identification and Localization

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JDK 18国际化指南：Java SE 18国际化技术详解

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