What do you mean by Class and Object in Java?

In Java, a class and an object are fundamental concepts in object-oriented programming. Let's explore what each term means:

1. Class:
   • A class is a blueprint or template that defines the structure and behavior of objects. It serves as a blueprint for creating objects of a specific type.
   • In Java, a class defines the attributes (data members) and methods (functions) that objects of that class will have. Attributes represent the state of an object, while methods define the actions or behaviors that the object can perform.
   • A class provides a way to encapsulate data and behavior related to a specific entity or concept. It encapsulates the data and behavior into a single unit.
   • Classes in Java are defined using the class keyword, followed by the class name and the class body that contains the attributes and methods.

Example of a simple class in Java:

public class Person {
    // Attributes
    String name;
    int age;

    // Method
    public void sayHello() {
        System.out.println("Hello, my name is " + name + " and I am " + age + " years old.");
    }
}

2. Object:
   • An object is an instance of a class. It is a concrete realization or instantiation of the blueprint defined by a class.
   • In Java, you create objects based on the class template. Each object has its own set of attributes (data) and can invoke the methods (behavior) defined in the class.
   • Objects represent individual entities or instances that you want to model in your program.
   • You can create multiple objects from the same class, and each object can have its own unique state (attribute values).

Creating and using objects in Java:

public class Person {
    // Attributes
    String name;
    int age;

    // Method
    public void sayHello() {
        System.out.println("Hello, my name is " + name + " and I am " + age + " years old.");
    }
}
public class Main {
    public static void main(String[] args) {
        // Create objects of the Person class
        Person person1 = new Person();
        Person person2 = new Person();

        // Set attribute values for each object
        person1.name = "Alice";
        person1.age = 30;

        person2.name = "Bob";
        person2.age = 25;

        // Call methods on the objects
        person1.sayHello(); // Output: Hello, my name is Alice and I am 30 years old.
        person2.sayHello(); // Output: Hello, my name is Bob and I am 25 years old.
    }
}

In summary, a class defines the blueprint or template for creating objects, and an object is a concrete instance of that class with its own data and behavior. Objects allow you to model real-world entities and interact with them in your Java programs.