In Chapter 1, Unified Modeling Language Primer, we learned that behavioral diagrams illustrate how system components interact to form a system. We examined the following behavioral diagrams—activity diagram, interaction diagram, state Machine diagram, and use case diagram. It follows that behavioral design patterns are focused on the interaction of objects and classes in a system. The key component here is the interaction, also referred to as the communication between objects and classes.
The twelve behavioral design patterns presented in this chapter can be grouped into two subcategories—those that focus on classes and those that focus on objects. The following table details the subcategories:
| Object Scope | Class Scope |
| Chain of responsibility pattern | Interpreter pattern |
| Command pattern | Template method pattern |
| Iterator... |