SOLID + OOP principles

OOP 4 principles

• abstraction

• inheritance

• polymorphism

• data encapsulation

SOLID abbrev for?

• SRP - single responsibility principle

• OCP - open close principle

• LSP - Liskov substitution principle

• ISP - interface segregation principle

• DIP - dependency inversion principle

SRP - single responsibility principle

• avoids bloated classes - one class should have a single responsibility - a single reason to change

OCP - open close principle

A class should be open to extension and closed to change. → no need to retest old code, backward compatibility, adaptability

usually achieved through inheritance

LSP - Liskov substitution principle

• Subclass should be able to substitute parent class → if subclass implements a method and throws UnsupportedMethodException, that will break this!

ISP - interface segregation principle

Avoids bloated interfaces. Implement only interfaces if all the methods from it are needed, otherwise break the interface apart.

DIP - dependency inversion principle

• a high level class shouldn’t depend on a low level one. High level - declares the what, low level - declared the how, the details. Use Interface, abstraction instead if implementation dependencies

• An abstraction shouldn’t depend on implementations. If an implementation needs new feature, you shouldn’t modify the base abstraction.