The Power of Decoupling in OOP

First what is Decoupling ??
Encapsulating the behavior that have several values.Decoupling encourage you to make another layer.
For Example
Suppose that u have animal class and another subclass class ( Dog , Bride ) this class inherit from animal as will and you need to add the capability of flying for this subclass , the best solution to do that is using Decoupling as following :-

public class animal {
      public Flys FlyingType  ;
}

public interface Flys{
      string fly();
}

class ItFly : Flys{

    public string fly(){

         return "It Can Fly";

       }

}

class CantFly : Flys{

     public string fly(){

         return "It Can not Fly";

       }

}

Now you can set and change the behavior in the fly.

You can also extend this behavior by add new class (FlySuperFast or FlyWithWings) without effect super-class or any subclass. 

The Negative for using Decoupling is increase number of object and class.

Look following UML for more information