OOPs in Java & 4 Pillars of OOPs, Advantages & Why It Matter

OOPs in Java: If we talk about java, the most important concept we need to know is OOPs. OOPs helps you to write clean, Organized and scalable code. Why oops is better than procedural is given

What is OOPs in Java

OOPs stands for Object Oriented Programming. It is a Java programming paradigm that focuses on creating objects that contain both data and behavior. Before starting the pillar of OOP, first we have to know about classes and objects.

Class

A class is a blueprint or, say, template of an object. It represent the set of properties or methods. Class is a logical entity. It is declared with the keyword class. And it does not take memory, but the object takes it when created.

Object

An object is the instance of a class. It is created from the class and actually holds the values of the properties and can use the methods. An object is a real entity, not logical like a class. It takes memory when it is created. In short, we say class is the template, and the object is the thing made from that template. While creating a home, first its map is passed; then, on the basis of that map, the home is made. Just like that, the home map is a class, and the home is a real entity like an object. It is created using a new keyword.

Benefits of Object-Oriented Programming:-

There are many Benefits of OOPs like:-

1. Modularity
2. Code reusability
3. Improved security
4. Flexible
5. Scalable
6. Maintainable

Pillar of Object Oriented Programming:-

The main four pillars of object-oriented programming are as follows:

1. Encapsulation
2. Abstraction
3. Inheritance
4. Polymorphism

1-Encapsulation

Binding of the data and methods together inside the single unit i.e class is called the encapsulation. It helps in hiding the internal data and access it by using getter and setter method. It is also known as data hiding. It is used for security reason.

Access Modifier

The Four Access modifier are as follows:-

Advantage and Disadvantage Of Encapsulation

2-Abstraction

To Hide the internal implementation and show only the necessary things is called Abstraction. For example: Switching on the fan no matter to know the mechanism of fan and its working. It is one of the most important pillar of the oops.
In Java we can achieve abstraction with abstract classes and interfaces.

Advantage and Disadvantage Of Abstraction

Inheritance

Inheritance means to pass the properties and methods of the parent class to its child class. For example, in real life, children have the properties of their parents, like some of your properties match your father’s.

This is the parent class
class Vehicle {
String color = “Black”;
int wheels = 4;

void start() {
System.out.println(“Vehicle is starting…”);
}
}

This is the Child Class which inherit the Vehicle class using extend keyword
class Car extends Vehicle {
String model = “Sedan”;

void showDetails() {
System.out.println(“Color: ” + color);
System.out.println(“Wheels: ” + wheels);
System.out.println(“Model: ” + model);
}
}

Types of Inheritance

The types of inheritance and differences are given below: –

Advantage and Disadvantage Of Inheritance

PolyMorphism

Polymorphism is made up of two greek words Poly=many, morph=forms. That allows objects to behave differently based on their specific class type. This means can take multiple forms.

Types of PolyMorphism

1. Compile-Time Polymorphism
2. Runtime Polymorphism

Advantage and Disadvantage Of Polymorphism

Common Interview Questions

1. What is OOP in Java?
2. Tell me how abstraction and encapsulation different?
3. What is method overloading?
4. What is method overriding?
5. What is inheritance?
6. Can Java support multiple inheritance?
7. What is polymorphism?
8. Java is a pure OOPs ? Why?

For official documentation, see Oracle Java Tutorials

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