What is the difference between a facade pattern and an adapter pattern in the context of software design?

The Facade pattern and the Adapter pattern solve different problems in software design, although both serve to simplify interaction with subsystems.

• The Facade provides a simplified interface to a complex system or set of classes. It hides complexity and implementation details, allowing the client to work with a single simple interface.

• The Adapter is used to convert the interface of one class into the interface expected by the client. It allows working with incompatible interfaces by 'adapting' one to the other.

Example:

• Facade: you have a complex library for working with databases, file systems, and networks. The facade combines these operations into a simple method saveData(), hiding the details.

• Adapter: you have a class with a method oldMethod(), and the client expects newMethod(). The adapter implements newMethod(), internally calling oldMethod().

In summary:

• The Facade simplifies the use of a complex system.
• The Adapter ensures compatibility between different interfaces.