6.11. (Optional) Software Engineering Case Study: Identifying Objects’ States and Activities in the ATM System

In Section 5.14, we identified many of the class attributes needed to implement the ATM system and added them to a class diagram (Fig. 5.28). In this section, we show how these attributes represent an object’s state. We identify some key states that our objects may occupy and discuss how objects change state in response to various events occurring in the system. We also discuss the workflow, or activities, that objects perform in the ATM system. We present the activities of the BalanceInquiry and Withdrawal transaction objects.

State Machine Diagrams

Each object in a system goes through a series of discrete states. An object’s current ...

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