And this implementation is closed: After you compile the FulfillmentGenerator class, you can't extend the invoice method to new types without editing the source code and recompiling.

此实现是封闭的：在您编译FulfillmentGenerator类以后，在不编辑源代码和重新编译的情况下，您无法将invoice方法扩展到新的类型。

youdao

And this implementation is closed: After you compile the FulfillmentGenerator class, you can't extend the invoice method to new types without editing the source code and recompiling.

此实现是封闭的：在您编译FulfillmentGenerator类以后，在不编辑源代码和重新编译的情况下，您无法将invoice方法扩展到新的类型。

youdao