状态机图通过对类对象的生存周期建立模型来描述对象随时间变化的动态行为，也可以用来描述用例、协作和方法的动态行为，它是展示状态与状态转换的图-State machine diagram of the class object through the life cycle of the object model to describe the dynamic behavior over time, can also be used to describe the use case, collabor