用a | a格式写的剩余字母的值如果已没有字母，则该值为空；否则，递归调用该模板。

The value of the remaining letters written in the a | a format. If there are no letters left, the value is empty; otherwise, you call the template recursively.

youdao

如果字符串不能为空或者必须为特定格式，请检查格式并抛出异常。

If the string can't be empty or must be in a specific format, check for the format and throw an exception.

youdao

xml类型字段包含一个完整的、格式规范的抑或模式有效的文档(或者为空)。

An XML-type field contains a complete, well-formed, optionally schema-valid document (or null).

youdao

比如，在发现的href为空的地方不需要添加链接—格式良好的文档不应该出现这种情况，但是有时候确实会出现。

For instance, you don't need to add cases where the found href is null - something that shouldn't happen with a well-formed document but sometimes does.

youdao

比如，在发现的href为空的地方不需要添加链接—格式良好的文档不应该出现这种情况，但是有时候确实会出现。

For instance, you don't need to add cases where the found href is null - something that shouldn't happen with a well-formed document but sometimes does.

youdao