What are Classes and Objects in Java? Java में Classes और Objects क्या हैं?

// Class Definition
public class Student {
    // Attributes (Member Variables)
    private String name;
    private int rollNumber;
    private double gpa;
    
    // Constructor
    public Student(String name, int rollNumber) {
        this.name = name;
        this.rollNumber = rollNumber;
        this.gpa = 0.0;
    }
    
    // Methods
    public void study() {
        System.out.println(name + ' is studying');
    }
    
    public void setGPA(double gpa) {
        this.gpa = gpa;
    }
    
    public double getGPA() {
        return gpa;
    }
}

// Creating Objects (Instances)
public class Main {
    public static void main(String[] args) {
        // Object creation
        Student student1 = new Student('John', 101);
        Student student2 = new Student('Jane', 102);
        
        // Using objects
        student1.study();
        student1.setGPA(3.8);
        System.out.println('GPA: ' + student1.getGPA());
    }
}

// Key Differences:
// Class: Blueprint, template, logical entity
// Object: Instance of class, physical entity created in memory
// One class can have multiple objects
// Objects consume memory, class does not