Factory Method Pattern in Java

This asset describes the Factory Method Pattern implementation in Java

interface CarPlant {
 
 //This is the factory method
 public Car createCar(String str);
}

//This class is one of the 'Concrete Creator' class. It implements the CarPlant interface.
class CarAPlant implements CarPlant{
 
 //This method returns the object of Car type
 public Car createCar(String str){
  if(str.equals("Petrol")){
   
   //returns an object of type CarAPetrol
   return new CarAPetrol();
  }else{
   
   //returns an object of type CarADiesel
   return new CarADiesel();
  }
 }
}

//This class is one of the 'Concrete Creator' class. It implements the CarPlant interface.
class CarBPlant implements CarPlant {
 
 //This method returns the object of Car type
 public Car createCar(String str){
  if(str.equals("Petrol")){
   
   //returns an object of type CarBPetrol
   return new CarBPetrol();
  }else{
   
   //returns an object of type CarADiesel
   return new CarBDiesel();
  }
 }
}

//This is the abstract 'Product' class. All the products must extend this class
abstract class Car {
 
 //Abstract method display.
 public abstract void display();
}

class CarAPetrol extends Car{
 
 //Implements the abstract method display() of the superclass Car.
 public void display(){
  System.out.println("This is a Petrol variant of CarA");
 }
}

class CarADiesel extends Car{
 
 //Implements the abstract method display() of the superclass Car.
 public void display(){
  System.out.println("This is a Diesel variant of CarA");
 }
}

class CarBPetrol extends Car{ 
 //Implements the abstract method display() of the superclass Car.
 public void display(){
  System.out.println("This is a Petrol variant of CarB");
 }
}

class CarBDiesel extends Car{
 
 //Implements the abstract method display() of the superclass Car.
 public void display(){
  System.out.println("This is a Diesel variant of CarB");
 }
}

public class FactoryPatternClass {
 //This is the 'Creator' Interface which contains the factory method
 public static void main(String args[]){
  Car car;
  CarPlant carAObj = new CarAPlant();
  CarPlant carBObj = new CarBPlant();
  //car has the reference to the type CarA
  car= carAObj.createCar("Diesel");
  
  //Calls the display method of the CarA class
  car.display();
  //car now has the reference to the type CarB
  car= carBObj.createCar("Diesel");
  //Calls the display method of the CarB class
  car.display();
  }
}