OOP is all about Encapsulation Yes, that’s right. Object Oriented Programming aims to encapsulate properties and methods into a consolidated object so that’s operations can be carried out on the object. The whole aim was to move from procedural functions which were not easy to reason about and prove correctness. But this principle often gets violated and people write procedural code using objects. Classic Example is: class Rectangle { private Long length; private Long breadth; //gettters //setters //constructors } And caller calculates area by: