add i18n in Java

Author: madawei2699

content/_index.md

@@ -7,6 +7,12 @@ outputs = ["Reveal"]
 
 ---
 
+## 2021
+
+- [i18n in Java](./i18n_java/)
+
+---
+
 ## 2020
 
 - [流量研究](./web_traffic_research/)

content/i18n_java/_index.md

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++++
+title = "i18n in Java"
+outputs = ["Reveal"]
++++
+
+## i18n in Java
+
+---
+
+### G11N/i18N/L10N
+
+![](https://img.bmpi.dev/53875fc9-00ac-e8e2-8d91-06399755dcba.png)
+
+> Internationalization is the process of designing an application so that it can be adapted to various **languages** and **regions** <ins>without engineering changes</ins>.
+
+---
+
+An internationalized program has the following characteristics:
+
+- With the <ins>addition of localized data</ins>, the <ins>same executable</ins> can run worldwide.
+- Textual elements, such as status messages and the GUI component labels, are <ins>not hardcoded</ins> in the program. Instead they are stored outside the source code and <ins>retrieved dynamically</ins>.
+- Support for <ins>new languages</ins> does not require recompilation.
+- Culturally-dependent data, such as <ins>dates and currencies</ins>, appear in formats that conform to the end user's region and language.
+- It can be <ins>localized quickly</ins>.
+
+---
+
+### Java i18n Demo
+
+```java
+import java.util.Locale;
+import java.util.ResourceBundle;
+
+public class Hello {
+
+    public static void main(String[] args) {
+        String language = "en";
+        String country = "US";
+
+        if (args.length == 1) {
+            language = args[0];
+        } else if (args.length == 2) {
+            language = args[0];
+            country = args[1];
+        }
+
+        var locale = new Locale(language, country);
+        var messages = ResourceBundle.getBundle("messages", locale);
+
+        System.out.print(messages.getString("hello") + " ");
+        System.out.println(messages.getString("world"));
+    }
+}
+```
+
+---
+
+messages_en.properties
+```
+hello=Hello(en)
+world=World
+```
+
+messages_en_US.properties
+```
+world=World(en_US)
+```
+
+messages_es.properties
+```
+hello=Hola
+world=Mundo
+```
+
+execute java
+```
+java Hello.java
+java Hello.java es
+```
+
+{{% fragment %}}
+
+```
+Hello(en) World(en_US)
+Hola Mundo
+```
+
+{{% /fragment %}}
+
+---
+
+### Java i18N workflow
+
+1. Create the Properties Files
+```
+greetings = Hello
+farewell = Goodbye
+inquiry = How are you?
+```
+2. Define the **Locale**
+```
+aLocale = new Locale("en","US");
+```
+3. Create a **ResourceBundle**
+```
+messages = ResourceBundle.getBundle("MessagesBundle", currentLocale);
+```
+```
+MessagesBundle_en_US.properties
+MessagesBundle_fr_FR.properties
+MessagesBundle_de_DE.properties
+```
+4. Fetch the Text from the ResourceBundle
+```
+String msg1 = messages.getString("greetings");
+```
+
+---
+
+How does an internationalized program identify the appropriate language and region of its end users?
+
+{{% fragment %}}
+
+It references a <ins>Locale</ins> object.
+
+{{% /fragment %}}
+
+---
+
+{{% section %}}
+
+### Locale in i18N
+
+> Locale is the user-specific location and cultural information managed by a computer. [(RFC6365)](https://datatracker.ietf.org/doc/html/rfc6365)
+
+> A concept or identifier used by programmers to represent a particular collection of cultural, regional, or linguistic preferences.
+
+---
+
+### Tags for Identifying Languages(BCP 47)
+
+![](https://img.bmpi.dev/d1feae2e-8820-2112-2354-60b8de71589c.png)
+
+```
+langtag = language["-" script]["-" region]*("-" variant)*("-" extension)["-" privateuse]
+```
+
+---
+
+### i18N IETF Standard
+
+- [Terminology Used in Internationalization in the IETF](https://datatracker.ietf.org/doc/html/rfc6365)
+- [IETF BCP<sub>Best Current Practice</sub> 47<sup>Language Tag Registry Update (LTRU)</sup>](https://www.rfc-editor.org/info/bcp47)
+- [Making Sense of Language Tags](https://www.slideserve.com/shantell/making-sense-of-language-tags)
+
+---
+
+### Locale in Java
+
+[java.util.Locale](https://github1s.com/openjdk/jdk/blob/master/src/java.base/share/classes/java/util/Locale.java)
+
+- Implements IETF [BCP 47](https://www.rfc-editor.org/info/bcp47)
+  - [RFC 4647](https://www.rfc-editor.org/rfc/rfc4647.txt): Matching of Language Tags
+    - <em>Filtering</em> is used to get all matching locales
+    - <em>lookup</em> is to choose the best matching locale
+  - [RFC 5646](https://www.rfc-editor.org/rfc/rfc5646.txt): Tags for Identifying Languages
+- Refers to IETF [RFC 2616](https://www.rfc-editor.org/rfc/rfc2616.txt)
+  - [Quality Values](https://datatracker.ietf.org/doc/html/rfc2616#section-3.9)
+- Refers to ISO
+  - [ISO 639](https://www.iso.org/iso-639-language-codes.html): Language codes
+  - [ISO 3166](https://www.iso.org/iso-3166-country-codes.html): Country codes
+  - [ISO 15924](https://unicode.org/iso15924/iso15924-codes.html): Script code
+
+{{% /section %}}
+
+---
+
+How does Java get messages by locale identify?
+
+{{% fragment %}}
+
+It's <em>ResourceBundle</em>!
+
+{{% /fragment %}}
+
+---
+
+### ResourceBundle in Java
+
+[java.util.ResourceBundle](https://github1s.com/openjdk/jdk/blob/master/src/java.base/share/classes/java/util/ResourceBundle.java)
+
+<a href="http://www.gdzwk.com/#/blog/i18n"> <img src="https://img.bmpi.dev/b542cf39-3946-24ed-a492-27f1f044d515.png" width="45%" height="45%" /></a>
+
+---
+
+### Others for i18N
+
+- [Common Language Data Repository(CLDR)](http://cldr.unicode.org/)<sup>Incorporated into JDK 8</sup>
+  - <ins>Locale-specific patterns for formatting and parsing</ins>: dates, times, timezones, numbers and currency values, measurement units,…
+  - <ins>Translations of names</ins>: languages, scripts, countries and regions, currencies, eras, months, weekdays, day periods, time zones, cities, and time units, and sequences (and search keywords),…
+  - <ins>Language & script information</ins>: characters used; plural cases; gender of lists; capitalization; rules for sorting & searching; writing direction; transliteration rules;…
+  - <ins>Country information</ins>: language usage, currency information, calendar preference, week conventions,…
+  - <ins>Validity</ins>: Definitions, aliases, and validity information for Unicode locales, languages, scripts, regions, and extensions,…
+- [UNICODE LOCALE DATA MARKUP LANGUAGE (LDML)](http://www.unicode.org/reports/tr35/)
+
+---
+
+### Outside of Java
+
+- [GUN gettext](https://www.gnu.org/software/gettext/)
+  - C
+  - C++
+  - Python
+  - PHP
+  - Elixir
+- [ICU](http://site.icu-project.org/)
+  - Code Page Conversion
+  - Collation
+  - Formatting(CLDR)
+  - Time Calculations
+  - Unicode Support
+  - Regular Expression
+  - Bidi
+  - Text Boundaries
+
+---
+
+### Further reading list
+
+- [Building a minimal i18n library](https://janmonschke.com/building-a-minimal-i18n-library)
+- [Clojure uses standard Java ResourceBundle](https://github.com/feldi/clojure-i18n/blob/master/src/i18n/core.clj)
+- [awesome-i18n](https://github.com/jpomykala/awesome-i18n)
+- [awesome-i18n](https://github.com/mrhota/awesome-i18n)
+- [国际化与本地化](https://www.bmpi.dev/dev/i18n-l10n/)
+- [国际化分析与处理](http://www.gdzwk.com/#/blog/i18n)