1. CSE115: Introduction to Computer Science I Dr. Carl Alphonce 219 Bell Hall Office hours: M-F 11:00-11:50 645-4739 alphonce@buffalo.edu

2. State systems State-based system: –system’s behavior based on its current state Many systems are state-based: –Cable/Satellite TV box –Wrist-watch –Cell phone interface

4. State Diagram OFFON push button

5. State Pattern example

6. Polymorphism Behavior determined by method of object, because… it’s the object that responds: –the type of the object determines response –the type of the reference to object doesn’t

7. Polymorphism declared type of variable a supertype of actual type of object

8. Proxy Pattern Polymorphism

9. Polymorphism (in proxy pattern) context delegates method call to concrete tool

10. State Pattern delegation

11. Delegation in State code public class DeskLamp { private IState _state; public DeskLamp() { _state = new Off(); } public void pushButton() { _state.pushButton(this); } public void setState(IState s) { _state = s; }