Which statement best describes the primary advantage of using composition over inheritance?

Which statement best describes the primary advantage of using composition over inheritance?

• A. It enforces an is-a relationship that can be overly rigid.
• B. It reduces coupling by delegating behavior to contained objects.
• C. It prevents polymorphism entirely.
• D. Composition reduces coupling and increases flexibility.

Answer: (D)

By favoring composition, you gain behavior by assembling objects that collaborate, rather than building a family of classes through inheritance. The main advantage is reduced coupling and greater flexibility: the containing class depends on the interfaces of its components, not on how a base class implements things. This lets you swap, mix, or extend components without changing a rigid inheritance hierarchy, making maintenance easier and enabling new behavior to be assembled at design time or even changed at runtime. Delegating tasks to contained objects is the mechanism that makes this possible, so you can achieve diverse functionality by recombining components rather than rewriting or reonly subclassing. Why this fits best is that it captures both the reduction in tight interdependencies and the ability to adapt behavior without sweeping changes across an inheritance tree. The alternative that mentions delegation touches on the mechanism but doesn’t emphasize the broader payoff—the overall design becomes more modular and adaptable. Inheritance, while it can model is-a relationships, often leads to tighter coupling and fragility as requirements evolve, and polymorphism isn’t blocked by composition.

By favoring composition, you gain behavior by assembling objects that collaborate, rather than building a family of classes through inheritance. The main advantage is reduced coupling and greater flexibility: the containing class depends on the interfaces of its components, not on how a base class implements things. This lets you swap, mix, or extend components without changing a rigid inheritance hierarchy, making maintenance easier and enabling new behavior to be assembled at design time or even changed at runtime. Delegating tasks to contained objects is the mechanism that makes this possible, so you can achieve diverse functionality by recombining components rather than rewriting or reonly subclassing.

Why this fits best is that it captures both the reduction in tight interdependencies and the ability to adapt behavior without sweeping changes across an inheritance tree. The alternative that mentions delegation touches on the mechanism but doesn’t emphasize the broader payoff—the overall design becomes more modular and adaptable. Inheritance, while it can model is-a relationships, often leads to tighter coupling and fragility as requirements evolve, and polymorphism isn’t blocked by composition.