Strategy Pattern

“Define a family of algorithms, encapsulate each one, and make them interchangeable.”

The Strategy pattern (GoF, 1994), also known as Policy, allows selecting an algorithm at runtime. Instead of hardcoding a single algorithm, the class delegates to a strategy object that implements a common interface. Swapping the strategy changes the behavior without modifying the client.

This favors composition over inheritance: behaviors are defined as separate interfaces and classes, decoupling the algorithm from the code that uses it. The client picks (or receives) the appropriate strategy, and the algorithm varies independently.