The Strategy pattern (also known as the policy pattern) is a design pattern whereby an algorithm's behavior can be selected at runtime. It is one of the Gang of Four's behavioral design patterns. When using this tag on implementation heavy questions - tag the code language the implementation is written in.
The intent of the strategy pattern is to "Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from the clients that use it."
The pattern relies heavily on composition. An important advantage of this approach over inheritance and simple method overrides is that the behavior can be freely changed at run-time by changing the object implementing it.
This pattern is one of the original design-patterns described in "Design Patterns" by Gamma, Helm, Johnson and Vlissides.
