# Annotations

`Annotations`（注解），`metadata`（愿数据）的一种形式，提供了程序的相关数据但并不是程序的一部分，注解不会影响它所标注的代码的运行。

注解有很多用途，其中有：

* **Information for the compiler**：编译器可以使用注解检测报错或者禁止警告。
* **Compile-time and deployment-time processing**：软件工具可以处理注释信息用以生成代码，XML文件等。
* **Runtime processing**：有些注释可以在运行时被检查。

这几章我们将说明哪里可以使用注释，怎么应用注释，JavaSE平台(Java SE API)可用的预定义注释类型，类型注解何如结合可插入类型系统来编写强类型检查的代码，以及如何实现重复注解。


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://eric3wade.gitbook.io/java/learning-the-java-language/annotations.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.