Object-Orientated Programming principles

There are four main OOPs concepts in Java. These are:

Abstraction. Abstraction means using simple things to represent complexity. We all know how to turn the TV on, but we don’t need to know how it works in order to enjoy it. In Java, abstraction means simple things like objects, classes, and variables represent more complex underlying code and data. This is important because it lets avoid repeating the same work multiple times.

Encapsulation. This is the practice of keeping fields within a class private, then providing access to them via public methods. It’s a protective barrier that keeps the data and code safe within the class itself. This way, we can re-use objects like code components or variables without allowing open access to the data system-wide.

Inheritance. This is a special feature of Object Oriented Programming in Java. It lets programmers create new classes that share some of the attributes of existing classes. This lets us build on previous work without reinventing the wheel.

Polymorphism. This Java OOPs concept lets programmers use the same word to mean different things in different contexts. One form of polymorphism in Java is method overloading. That’s when different meanings are implied by the code itself. The other form is method overriding. That’s when the different meanings are implied by the values of the supplied variables.

Polymorphism in Java works by using a reference to a parent class to affect an object in the child class.
Two more examples of polymorphism in Java are method overriding and method overloading.

In method overriding, the child class can use the OOP polymorphism concept to override a method of its parent class. That allows a programmer to use one method in different ways depending on whether it’s invoked by an object of the parent class or an object of the child class.

In method overloading, a single method may perform different functions depending on the context in which it’s called. That is, a single method name might work in different ways depending on what arguments are passed to it.