Strategy is a very generic design pattern with many use cases. In general, whenever we want to be able to apply different algorithms dynamically and transparently, Strategy is the way to go. By different algorithms, I mean different implementations of the same algorithm. This means that the result should be exactly the same, but each implementation has a different performance and code complexity (as an example, think of sequential search versus binary search).

We have already seen how Python and Java use the Strategy pattern to support different sorting algorithms. However, Strategy is not limited to sorting. It can also be used to create all kinds of different resource filters (authentication, logging, data compression, encryption, and so forth) [j.mp/javaxfilter].

Another usage of the Strategy pattern is to create different formatting representations, either to achieve portability (for example, line-breaking differences between platforms) or dynamically change the representation...