Part 1 — Definition

A Class is a user-defined blueprint from which objects are created. It represents the set of properties or methods that are common to all objects of one type. An Object is a basic unit of Object-Oriented Programming and represents real-life entities.

Part 2 — Syntax

class ClassName {
    // Fields (Attributes)
    // Methods (Behaviors)
}

ClassName obj = new ClassName(); // Object creation

Part 3 — Example

Problem: Model a simple "Car" with a brand and a method to start.

class Car {
    String brand;
    void drive() {
        System.out.println(brand + " is driving...");
    }
}

public class Main {
    public static void main(String[] args) {
        Car myCar = new Car();
        myCar.brand = "Tesla";
        myCar.drive();
    }
}

Part 4 — Video

Video: Coming Soon

Part 1 — Definition

A Constructor is a special method that is used to initialize objects. It is called when an object of a class is created. It has the same name as the class and no return type. If you don't define one, Java provides a "Default Constructor".

Part 2 — Syntax

class Student {
    Student() {
        // Initialization code
    }
}

Part 3 — Example

Problem: Initialize a student's name and roll number at the time of creation.

class Student {
    String name;
    int roll;

    Student(String n, int r) {
        name = n;
        roll = r;
    }
}

Observation: Constructors ensure that an object is never in an invalid state after creation.

Part 4 — Video

Video: Coming Soon