Polymorphism: More Than Just Method Definitions

In object-oriented programming, interfaces play a crucial role in ensuring code flexibility and reusability. While you correctly state that interfaces only require classes that implement them to provide the necessary methods, their true value extends far beyond method declaration.

Consider the example you provided, using the IBox interface and a Rectangle class. Creating an instance of IBox directly is not possible, as interfaces themselves are not intended to be instantiated. Instead, you instantiate the Rectangle class, which implements the IBox interface. This ensures that Rectangle has the required methods specified in the interface.

However, the true power of interfaces lies in their ability to enable polymorphism. For example, you could create a list of IBox objects, which could contain instances of different classes that implement IBox, such as Rectangle, Square, or Circle.

You can then perform operations on each box in the list using the methods defined in IBox, even though the actual class of each box may vary. This eliminates the need to check the concrete type of each box and allows you to treat them all as IBox objects.

In summary, interfaces provide more than just method signatures. They facilitate polymorphism, allowing you to work with different implementations of the same abstract concept through a common interface. By decoupling the interface from its implementations, you gain flexibility, reusability, and easier maintenance of your codebase.