Managing Complex Logic
While Creational patterns (Factory) and Structural patterns (Decorator) handle object setup, Behavioral patterns handle the "Brain" of your system. They define how objects communicate and how state transitions occur.
1. The Finite State Machine (FSM)
In many interviews (Vending Machine, ATM, Workflow Engine), your object must change its behavior based on its internal state. The State Pattern allows you to do this without nested switch statements.
2. Curriculum in this Module
- Theory: Advanced Behavioral logic (Current Page)
- Case Study: The State Pattern (Vending Machine) - Mastering transitions.
- Lesson: Chain of Responsibility - Building request middleware.
- Lesson: Command Pattern - Implementing Undo/Redo and Remote Controls.
3. Chain of Responsibility
Used when more than one object can handle a request.
- Real-world: A technical support line. Tier 1 handles basic stuff, escalates to Tier 2 if needed, then Tier 3.
- Code: Used in Servlet Filters and Logging Loggers.
4. Command Pattern
Encapsulates a request as an object.
- Real-world: A waiter taking an order. The "Order" is the command. It can be queued, delayed, or cancelled.
Final Takeaway
Mastering these patterns separates the "Senior" from the "Lead" developer. It shows you can architect systems that handle complex business workflows with ease.