Final answer:
In the context of programming, when a class implements an interface, it must provide concrete implementations for all of the methods declared in the interface. This creates a contract that ensures consistency and enables polymorphism, allowing objects of the implementing class to be treated as objects of the interface type.
Step-by-step explanation:
When a class implements an interface, it agrees to adhere to the contract defined by the interface. This contract is formed by the methods declared within the interface. By implementing an interface, a class agrees to provide concrete implementations for all of the abstract methods defined in the interface. If a class declares an interface but does not provide implementations for all of the methods defined therein, the class must be declared as abstract. Conversely, a non-abstract class that implements an interface is compelled to provide specific functionality for each method defined by the interface, thereby facilitating a form of polymorphism. This ensures consistency and allows for objects of the implementing class to be treated as objects of the interface type.
For example, in a Java program, an interface AudioPlayer might have a method called play(). Any class that implements this interface would need to provide a concrete instance of the play method, detailing exactly how the audio will be played.
Interfaces serve as a blueprint, allowing different classes to share a common set of functionalities, despite having potentially different implementations. It promotes the design principle of 'programming to an interface, not an implementation,' fostering flexibility and extensibility in software architecture.