Java method overriding in class inherit

class Animal {
   public void displayInfo() {
      System.out.println("This is an animal.");
   }
}

class Dog extends Animal {
   @Override
   public void displayInfo() {
      System.out.println("This is a Dog.");
   }
}

class Main {
   public static void main(String[] args) {
   	  
      Animal a1 = new Animal();
      a1.displayInfo();
	  
      Dog d1 = new Dog();
      d1.displayInfo();
   }
}

output:

This is an Animal.
This is a Dog.