Question

Distinguish between inheriting interface and inheriting implementation. How do inheritance hierarchies designed for inheriting interface differ from those designed for inheriting implementation?

Short answer

Inheriting interfaces focuses on fulfilling a contract via method signatures, while inheriting implementations reuses code. Interface hierarchies are flatter and more flexible, whereas implementation hierarchies tend to be deeper with tighter dependencies.

Step-by-step solution

Understanding Interfaces

When you inherit an interface, you're focusing on defining a contract or a set of methods that a class must implement. An interface doesn't provide any method implementations, only their signatures. Therefore, when you create a hierarchy that inherits interfaces, you ensure that various classes can promise to provide specific functionality without imposing how that functionality should be achieved. This promotes design flexibility and allows multiple classes to implement the same interface in different ways.

Understanding Implementation Inheritance

Inheriting implementation refers to using a superclass to provide common functionality that is passed down to subclasses. This form of inheritance allows classes to reuse code, reducing redundancy. The superclass contains methods with actual code implementations, which subclasses can use directly or override if needed. This approach fixes certain behaviors in superclasses and relies on subclasses primarily for enhancements or specific adaptations.

Comparison of Hierarchies

Inheritance hierarchies designed for inheriting interfaces are typically flatter because each class implements interfaces independently, allowing for greater flexibility and adaptability. In contrast, those designed for inheriting implementation often have deeper hierarchies. This is because classes are structured to extend and refine functionality over a chain of superclasses, likely creating more dependencies and a tighter inheritance tree.

Key concepts

Interface Inheritance

Interface inheritance focuses on defining a set of methods that a class must implement. Think of it as a contract that classes sign up to, to ensure they provide specific functionalities. Interfaces only include method signatures without any actual code to execute. This means the method itself doesn't dictate how to carry out the tasks but just declares what tasks need to be performed.

This type of inheritance is highly flexible and promotes consistency across different classes. By following an interface, various classes can implement the same methods but execute them in different ways based on their specific requirements.

One benefit is that it allows multiple classes to adhere to the same set of guidelines, which can make your code base more organized and easier to maintain. Since interfaces do not carry any implementation details, they offer the flexibility to adapt and change without affecting other parts of the code.

Implementation Inheritance

Implementation inheritance is about reusing code through a superclass. This means a class acquires methods and properties from a parent class, which includes actual code implementations. It reduces redundancy as subclasses can use the functionality provided by superclasses right out of the box.

Here's how it works:

• Subclasses automatically inherit the methods from the superclass, cutting down on repeated code writing.
• If needed, subclasses can override or extend these methods to add new behavior.

This approach is powerful for cases where many classes share the same functionality. By defining those common methods in a superclass, you ensure a consistent implementation and centralized management.

However, since it fixes specific behaviors within the superclass, changing superclass behavior can have widespread effects on all subclasses. This can sometimes lead to rigid structures or require careful management to avoid unintended changes.

Inheritance Hierarchies

Inheritance hierarchies differ significantly when comparing interface and implementation inheritance. With interface inheritance, hierarchies tend to be flatter. Each class stands independently and can implement interfaces in various ways. This leads to more adaptable designs where classes implement functionality as needed without being tied to a specific structure.

In contrast, implementation inheritance often results in deeper hierarchies. Classes extend and build upon the functionality of ancestors, creating layers of inheritance. This can lead to complex hierarchies with multiple levels where subclasses depend on superclasses for their behavior.

Here's a quick comparison:

• Interface inheritance promotes loose coupling among classes, facilitating more agile and flexible architecture changes.
• Implementation inheritance can form tightly coupled hierarchies, leading to less flexibility but possibly stronger integration among related classes.

Understanding these differences is key to designing effective inheritance structures that suit your programming goals.