1. DuckFactory

2. MallardDuck

3. RedheadDuck

4. RubberDuck

5. DuckCall

6. Goose

7. GooseAdapter

8. Flock

9. CountingDuckFactory

10. Observable

11. QuackCounter

12. Quackologist

13. DuckSimulator

DuckFactory

MallardDuck

RedheadDuck

RubberDuck

DuckCall

Goose

GooseAdapter