Introduction to Object-Oriented Programming (OOP)

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Arjit Sharma
01 Min

What is OOP ?

Object-Oriented Programming is a paradigm centered around the concept of objects - real-world entities that have attributes (data) and behaviors (methods).

tbh a fancy way of saying “Let’s write code that feels more like the real world”

In Java, everything revolves around classes and objects, making OOP a fundamental skill for every Java developer.

—

Classes and Objects

Blueprint or a template are used to create objects. java.lang.Object is the superclass of all classes in java.

class Person {
	String name;
	int age;
	
	// Constructor
	public Person(){
		name="";
		age=0;
	}
	
	void sleeps(int hours){
		System.out.println("This person sleeps " + hours + " hours");
	}
	
}

public class Main{
	public static void main(String s[]){
		Person p1 = new Person();
		p1.age=25;
		p1.name="arjit";
		p1.sleeps(6);
	}
}

Constructor - A constructor only exists in the context of creating a new instance or object of a class.

Encapsulation

Practice of bundling the data (attributes) and methods (functions) that operate on the data into a single unit (class), and restricting access to some of the object’s components.

Package - A java package is a group of similar types of classes, interfaces and sub-packages.

Access Modifiers

  • public: Accessible from anywhere.
  • private: Accessible only within the class.
  • protected: Accessible within package and subclasses.
  • Default (no modifier): Accessible within package only.
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