In which cases is it recommended to use interfaces in software system design?

Interfaces are recommended for use in the following cases:

• When you need to define a contract that different classes must implement, ensuring polymorphism.
• To separate abstraction from implementation, which facilitates component replacement and testing.
• When designing modular and extensible systems, where different parts can interact through interfaces.
• To simplify maintenance and scaling of code, especially in large teams.

For example, in Android, you can define an interface for handling clicks, which is implemented by different activities or fragments, regardless of the specific implementation.