What is a Class in Java?

A class in Java is a blueprint or template used to create objects. It defines the properties (fields) and behaviors (methods) of an object.

Basic Syntax of a Class

class ClassName {
    // fields (variables)
    // methods
}

Example 1: Basic Class with Object Creation

// Define a class
class Car {
    // fields
    String brand = "Toyota";
    int speed = 120;

    // method
    void displayInfo() {
        System.out.println("Brand: " + brand);
        System.out.println("Speed: " + speed + " km/h");
    }
}

// Main class
public class Main {
    public static void main(String[] args) {
        // create an object of Car
        Car myCar = new Car();
        myCar.displayInfo(); // call method
    }
}

Output:

Brand: Toyota
Speed: 120 km/h

Example 2: Class with Constructor and Parameters

class Student {
    String name;
    int age;

    // constructor
    Student(String n, int a) {
        name = n;
        age = a;
    }

    void showDetails() {
        System.out.println("Name: " + name);
        System.out.println("Age: " + age);
    }
}

public class Main {
    public static void main(String[] args) {
        Student s1 = new Student("Alice", 20);
        s1.showDetails();
    }
}

Output:

Name: Alice
Age: 20

Components of a Class

Example 3: Multiple Objects from One Class

class Dog {
    String breed;

    void bark() {
        System.out.println(breed + " is barking!");
    }
}

public class Main {
    public static void main(String[] args) {
        Dog d1 = new Dog();
        d1.breed = "Labrador";
        d1.bark();

        Dog d2 = new Dog();
        d2.breed = "Pug";
        d2.bark();
    }
}

Output:

Labrador is barking!
Pug is barking!

Why Use Classes?

• To organize code using Object-Oriented Programming (OOP)
• To model real-world things (like Car, Student, Dog)
• For reusability and modularity

Keywords Related to Classes

• class – to define a class
• new – to create an object
• this – refers to the current object
• static – to define class-level fields or methods