What is an Object?

About

In Java, an object is an instance of a class that contains state (fields/variables) and behavior (methods). Objects are created based on the blueprint defined by a class.

Characteristics of an Object

1. State (Attributes)

   • Represented by instance variables (fields).

   • Stores the data or properties of the object.

2. Behavior (Methods)

   • Defined by functions inside the class.

   • Determines what actions an object can perform.

3. Identity (Reference)

   • Each object has a unique memory address in the heap.

Example of an Object

// Class Definition
class Car {
    String brand;  // Attribute
    int speed;

    // Constructor
    Car(String brand, int speed) {
        this.brand = brand;
        this.speed = speed;
    }

    // Method (Behavior)
    void accelerate() {
        speed += 10;
        System.out.println(brand + " is now going at " + speed + " km/h.");
    }
}

// Main Class
public class Main {
    public static void main(String[] args) {
        // Creating Objects
        Car car1 = new Car("Toyota", 50);
        Car car2 = new Car("Honda", 40);

        // Accessing Object Methods
        car1.accelerate();  // Toyota is now going at 60 km/h.
        car2.accelerate();  // Honda is now going at 50 km/h.
    }
}

How Objects Work in Memory

1. Objects are created in the heap memory.

2. The reference variable (like car1 and car2) points to the object in memory.

3. Multiple reference variables can point to the same object.

Car car3 = car1;  // Now both car1 and car3 point to the same object

When is the object created with new keyword

In Java, the object is created with the new keyword during runtime.

The new keyword plays a crucial role in the object creation process:

1. Memory Allocation: It triggers the allocation of memory for the new object on the heap. The heap is a special area of memory dedicated to storing objects in Java.

2. Constructor Call: It invokes the constructor of the class specified after new. The constructor is responsible for initializing the object's state by assigning values to its fields.

Therefore, the new keyword initiates object creation and memory allocation at runtime, not during compilation. This allows for dynamic object creation based on your program's needs.