The Strategy pattern

The Strategy pattern is a common demonstration of abstraction in object-oriented programming. The pattern implements different solutions to a single problem, each in a different object. The core class can then choose the most appropriate implementation dynamically at runtime.

Typically, different algorithms have different trade-offs; one might be faster than another, but uses a lot more memory, while a third algorithm may be most suitable when multiple CPUs are present or a distributed system is provided.

Here is the Strategy pattern in UML:

Figure 11.4: Strategy pattern in UML

The Core code connecting to the Strategy abstraction simply needs to know that it is dealing with some kind of class that fits the Strategy interface for this particular action. Each of the implementations should perform the same task, but in different ways. The implementation interfaces need to be identical, and it's often helpful to leverage an...