所有Javadoc注释均以一个块注释开头，后跟一个星号（/**），并在该块注释出现（*/）时结束。（可选）每行可以以任意空格和一个星号开头；生成文档文件时将忽略这些文件。
/**
* Fields can be documented as well.
*
* As with other javadocs, the documentation before the first period is used as a
* summary, and is usually separated from the rest of the documentation by a blank
* line.
*
* Documentation for fields can use inline tags, such as:
* {@code code here}
* {@literal text here}
* {@link other.docs.Here}
*
* Field documentation can also make use of the following tags:
*
* @since 2.1.0
* @see some.other.class.Documentation
* @deprecated Describe why this field is outdated
*/
public static final String CONSTANT_STRING = "foo";