Why is it important to declare base methods in an interface when designing a system?

Declaring basic methods in an interface during system design is important for ensuring contract-based programming and architectural flexibility. This allows:

• Defining a clear set of mandatory operations that must be implemented by all classes implementing the interface.
• Ensuring polymorphism, enabling work with different implementations through a common interface.
• Simplifying testing and component replacement without changing client code.
• Improving code readability and maintainability, as the interface serves as documentation for functionality.

For example, in Android, you can declare a Repository interface with basic methods getData() and saveData(), so that different implementations (such as local database or remote server) have the same contract.