Create two sub-directories under impl: include and lib.

在impl目录下创建两个子目录：include和lib。

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Create a directory impl under the application directory sample_spl.

在应用程序目录sample_spl下创建目录impl。

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Both are interfaces, with implementation classes within the sub-directory called impl.

这两个文件都是接口，类的实现在子目录impl下。

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