The document introduces design patterns and related concepts like object-oriented analysis and design (OOAD) and dependency injection. It uses the strategy pattern as an example, showing how interfaces can be used to allow different duck types to have different flying behaviors without complex conditional logic. Dependency injection is discussed as a way to decouple classes and allow flexibility in how dependencies are satisfied.

1. Design Patterns Abhishek Chatterjee

7. An Orientation Example – Strategy Pattern Duck quack() swim() abstract display() MallardDuck display() RedheadDuck display() Lots of other types of ducks

8. An Orientation Example – Strategy Pattern Duck quack() swim() abstract display() fly() MallardDuck display() RedheadDuck display() Lots of other types of ducks

9. An Orientation Example – Strategy Pattern Duck quack() swim() abstract display() fly() MallardDuck display() RedheadDuck display() Lots of other types of ducks

10. An Orientation Example – Strategy Pattern Duck quack() swim() abstract display() fly() MallardDuck display() RedheadDuck display() Yay!! I can fly too!!! RubberDuck display()

12. Hey Abbey-Shack…. If you want to try Monster.com’s resume services, now is the time.

13. Who is going to rescue me now? <<Interfaces>> !!! Yes!!! That’s it! I make an IFlyable interface and RubberDuck doesn’t get to implement it… MallardDuck <<IFlyable>> display() RedheadDuck <<IFlyable>> display() RubberDuck //You can’t fly! display() They can’t see me happy 

14. I… I… I… I have a Question! SimCorp simulates 50 ducks… are you saying you are going to write 50 fly methods? What if there is a change in flying style and it effects 20 ducks… will all 20 ducks change? I am losing money you know…

16. Strategy Pattern in Action Duck quack() swim() abstract display() MallardDuck IFlyBehavior:FlyWithWings display() RubberDuck IFlyBehavior: DontFly display() IFlyBehavior fly() FlyWithWings FlyWithRocket DontFly

20. Q & A

21. Thank You