Design Pattern: Strategy pattern.

Head First - Design Patterns: chapter 01 notes:

Design Principle
Identify the aspects of your application that vary and separate them from what stays the same.


Take what varies and “encapsulate” it so it won’t affect the rest of your code.
The result? Fewer unintended consequences from code changes and more flexibility in your systems!


Design Principle
Program to an interface, not an implementation.
“Program to an interface” really means “Program to a supertype.”


Design Principle
Favor composition over inheritance


The Strategy Pattern defines a family of algorithms, encapsulates each one, and makes them interchangeable. Strategy lets the algorithm vary independently from clients that use it.