Design Principle

Design Principle 1
Identify the aspects of your application that vary and
separate them from what stays the same

Design Principle 2
Program to an interface, not an implementation

Design Principle 3
Favor composition over inheritance.

Design Principle 4
Strive for loosely coupled designs between objects that interact

Design Principle 5 (Open-Closed Principle)
Classes should be open for extension, but closed for modification