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SOLID Principle

Single-responsiblity Principle​

Open-closed Principle​

Liskov Substitution Principle​

Subclasses should be substitutable for their base classes.

Given that class B is a subclass of class A, we should be able to pass an instance of class B to any method that expects an instance of class A and the method should not give any weird output in that case.

So in terms of functionality, subclass B should be a superset of superclass A.

Example​

Although in math, Square is a special case of Rectangle, letting Square class inherit Rectangle class violates Liskov Substitution Principle.

Square cannot replace Rectangle as its width and height are set together.

Interface Segregation Principle​

Dependency Inversion Principle​

References