[docs] Add code style guide

README.md

@@ -293,6 +293,19 @@ Addax	19890604	1989-06-04 00:00:00	true	test
 - [online](https://addax.readthedocs.io)
 - [project](docs/src/main/sphinx/index.rst)
 
+## Code Style
+
+We recommend you use IntelliJ as your IDE. The code style template for the project can be found in the [codestyle](https://github.com/airlift/codestyle) repository along with our general programming and Java guidelines. In addition to those you should also adhere to the following:
+
+* Alphabetize sections in the documentation source files (both in table of contents files and other regular documentation files). In general, alphabetize methods/variables/sections if such ordering already exists in the surrounding code.
+* When appropriate, use the Java 8 stream API. However, note that the stream implementation does not perform well so avoid using it in inner loops or otherwise performance sensitive sections.
+* Categorize errors when throwing exceptions. For example, PrestoException takes an error code as an argument, `PrestoException(HIVE_TOO_MANY_OPEN_PARTITIONS)`. This categorization lets you generate reports so you can monitor the frequency of various failures.
+* Ensure that all files have the appropriate license header; you can generate the license by running `mvn license:format`.
+* Consider using String formatting (printf style formatting using the Java `Formatter` class): `format("Session property %s is invalid: %s", name, value)` (note that `format()` should always be statically imported). Sometimes, if you only need to append something, consider using the `+` operator.
+* Avoid using the ternary operator except for trivial expressions.
+* Use an assertion from Airlift's `Assertions` class if there is one that covers your case rather than writing the assertion by hand. Over time we may move over to more fluent assertions like AssertJ.
+* When writing a Git commit message, follow these [guidelines](https://chris.beams.io/posts/git-commit/).
+
 ## License
 
 This software is free to use under the Apache License [Apache license](/LICENSE).

README_zh.md

@@ -350,6 +350,19 @@ Addax	19890604	1989-06-04 00:00:00	true	test
 - [在线文档](https://addax.readthedocs.io)
 - [项目内文档](docs/src/main/sphinx/index.rst)
 
+## 代码风格
+
+建议使用 IntelliJ 作为开发 IDE。项目的代码风格模板可以在[codestyle](https://github.com/airlift/codestyle)资源库中找到，还有我们的一般编程和Java指南。除了这些之外，你还应该遵守以下几点。
+
+* 在文档源文件中按字母顺序排列章节（包括目录文件和其他常规文档文件）。一般来说，如果周围的代码中已经存在这样的排序，就按字母顺序排列方法/变量/部分。
+* 在适当的时候，使用Java 8的流API。然而，请注意，流的实现并不是很好，所以避免在内循环或其他对性能敏感的部分使用它。
+* 在抛出异常时对错误进行分类。例如，AddaxException需要一个错误代码作为参数，`AddaxException(RdbmsReaderErrorCode)`。这种分类可以让你生成报告，这样你就可以监控各种故障的频率。
+* 确保所有文件都有适当的许可证头；你可以通过运行`mvn license:format`生成许可证。
+* 考虑使用字符串格式化（使用Java`Formatter`类的printf风格格式化）：`format("Session property %s is invalid: %s", name, value)`（注意，`format()`应该总是静态导入）。有时，如果你只需要附加一些东西，可以考虑使用`+`运算符。
+* 除了琐碎的表达式，避免使用三元操作符。
+* 如果有涵盖你的情况的断言，就使用Airlift的`Assertions`类，而不是手工写断言。随着时间的推移，我们可能会转移到更流畅的断言，如AssertJ。
+* 在编写Git提交信息时，请遵循这些[指南]（https://chris.beams.io/posts/git-commit/）。
+
 ## License
 
 This software is free to use under the Apache License [Apache license](/license.txt).