Which statement describes the Adapter pattern?

Which statement describes the Adapter pattern?

• A. Wraps an object to add behavior.
• B. Provides a global point of access for an instance.
• C. Converts one interface into another expected by clients to enable collaboration with incompatible classes.
• D. Defines an algorithm family only.

Answer: (C)

The Adapter pattern is about converting one interface into another so that clients can work with objects that have incompatible interfaces. It acts as a bridge: the client expects a certain interface (the one it knows how to use), while the real object provides a different one. The adapter wraps or holds the real object (the adaptee) and translates the client’s calls into the calls the adaptee understands, possibly adapting method names, parameters, or semantics. For example, if a client works with a Target interface that has a method request(), but you have an Adaptee with a different method like specificRequest(), an adapter can implement Target and internally call specificRequest() on the adaptee, performing any needed data transformation. This lets you reuse existing code without changing it, and lets new code work with legacy or third-party components. There are common ways to implement the adapter: by wrapping the adaptee inside the adapter (object adapter, via composition) or by inheriting from the adaptee and implementing the target interface (class adapter, where language rules allow). The key idea is the interface translation that enables collaboration between otherwise incompatible classes. Wrapping an object to add behavior is more characteristic of a decorator, which extends functionality without changing the interface. Providing a global point of access for an instance is the Singleton pattern, and defining an algorithm family without changing the algorithms themselves aligns with patterns like Strategy.

The Adapter pattern is about converting one interface into another so that clients can work with objects that have incompatible interfaces. It acts as a bridge: the client expects a certain interface (the one it knows how to use), while the real object provides a different one. The adapter wraps or holds the real object (the adaptee) and translates the client’s calls into the calls the adaptee understands, possibly adapting method names, parameters, or semantics.

For example, if a client works with a Target interface that has a method request(), but you have an Adaptee with a different method like specificRequest(), an adapter can implement Target and internally call specificRequest() on the adaptee, performing any needed data transformation. This lets you reuse existing code without changing it, and lets new code work with legacy or third-party components.

There are common ways to implement the adapter: by wrapping the adaptee inside the adapter (object adapter, via composition) or by inheriting from the adaptee and implementing the target interface (class adapter, where language rules allow). The key idea is the interface translation that enables collaboration between otherwise incompatible classes.

Wrapping an object to add behavior is more characteristic of a decorator, which extends functionality without changing the interface. Providing a global point of access for an instance is the Singleton pattern, and defining an algorithm family without changing the algorithms themselves aligns with patterns like Strategy.