These are the respective implementations of each abstract class and interface in the message queue framework interface package.

它们分别是消息队列框架接口包中每个抽象类和接口的实现。

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In this case, we use an abstract class to define the service interface and operations of the exposed capabilities, as shown in Figure 3.

在这种情况下，我们使用一个抽象的类，来定义服务接口以及预期功能的操作，如图3所示。

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Offering both an interface and an abstract class is redundant, but I find it convenient: in most cases, I only need the abstract class, but the interface enables multiple inheritance.

同时提供接口和抽象类是多余的，但我发现这样很方便：在大多数情况下，我只需要抽象类，但接口支持多继承性。

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