这些实例变量不能重新设置，如果它们不为空，则用于为每个请求提供用户名和密码。

These instance variables are not reset and, if they are not null, are used to provide the username and password on every request.

youdao

如果用户名和密码的其他两个来源为空，并且在每次使用后不能重新设置，则只能使用这些实例变量，所以每个请求都可能会使用它们。

These instance variables are only used if the other two sources of username and password are null, and are not reset after each use, so they can potentially be used on every request.

youdao

每次使用后，用户名和密码的线程本地存储值都被重新设置为空。

After each use, the thread local storage values of username and password are reset to null.

youdao