序列图和 Java
我正在阅读有关序列图的内容，并且发现了一个涉及 Java 代码的练习（多项选择），它让我有点困惑......你能帮我选择正确的选项，以便让我更清楚吗？我想这对你来说很简单。非常感谢。
这是图像的直接链接（托管在 ImageShack 中）： 序列图和 Java
您会选择什么答案？
I'm reading about Sequence Diagrams and I've found an exercise (multiple choice) which envolves Java code and it got me kind of confused... Can you help me to choose the right option, in order to get it clearer for me? I think it'd be simple for you. Many thanks in advance.
Here's the direct link to the image (hosted in ImageShack):
Sequence Diagrams and Java
What answer would you choose?
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评论（2）
该图显示了一个进程调用 as()，该进程调用 cw()，后者调用 du()，后者调用 at()。
所以a上的functions()必须包含cw()。
你能将这个逻辑应用到其余的箭头吗？
The diagram shows a process calling a.s() which calls c.w(), which calls d.u(), which calls a.t().
So functions() on a must include c.w().
Can you apply that logic to the rest of the arrows?
一个提示：右侧提供的类图与寻找答案并不真正相关。
另一个提示：从 d 到 at() 的调用与其他调用不同，它只是返回而不是调用另一个方法。
备注：在Java中，所有方法调用最终都会返回或抛出异常，除非系统提前退出。这使得这个序列图有点奇怪——只有一个方法调用（我上面提到的那个）显示返回。该图的其余部分显示了类之间来回的方法调用链。这不是 Java 中类协作的常见方式，似乎纯粹是为了测试您对 UML 的理解而构建的。
One hint: the class diagram provided on the right is not really relevant to finding the answer.
Another hint: the call from d to a.t() is different from the other calls in that it just returns instead of calling another method.
A remark: in Java, all method calls ultimately return or throw an exception unless the system exits prematurely. This makes this sequence diagram a bit odd - only one of the method calls (the one I mention above) is shown to return. The rest of the diagram shows a chaining of method calls to-and-fro between classes. This is not a common way classes collaborate in Java and seems to be constructed purely to as an excercise to test your understanding of UML.