Some badly written code to help learn and practice polymorphism concepts

Car.java

// File: Car.java
// Author: David Ginzberg
// Purpose: A small metaphorical program for practicing polymorphic 
//  code design and using interfaces
package polymorphism;

public class Car{
    private enum Model{
        CIVIC, CHARGER, Z4, JETTA;
    }
    protected enum Fuel{
        REGULAR, MIDGRADE, PREMIUM, DIESEL, AVGAS;
    }
    
    Model model;
    Fuel fuel;
    public Car(){
      model = Model.CIVIC;
      fuel = Fuel.REGULAR;
    }
    
    public Car(int whichOne){
        switch(whichOne){
          default:
          case 1:
              model = Model.CIVIC;
              fuel = Fuel.REGULAR;
              break;
          case 2:
              model = Model.CHARGER;
              fuel = Fuel.MIDGRADE;
              break;
          case 3:
              model = Model.Z4;
              fuel = Fuel.PREMIUM;
              break;
          case 4:
              model = Model.JETTA;
              fuel = Fuel.DIESEL;
              break;
        }
    }
        

    public void drive(){
        System.out.println("Driving my " + this);
    }

    public void refuel(){
        System.out.println("Refuelling my " + this + " with " + fuel.name());
    }
    
    public void testEmissions(){
        System.out.println("Emissions test for " + this + ". It passed.");
        if(model == Model.JETTA && fuel == Fuel.DIESEL){
            System.out.println("...But something's fishy...");
        }
    }
    public String toString(){
        return model.name();
    }
}

TestDrive.java

// File: Car.java
// Author: David Ginzberg
// Purpose: Driver class for Car.java example
package polymorphism;
import polymorphism.Car;

public class TestDrive{
    public static void main(String[] args){
        Car[] myCars = {
            new Car(1),
            new Car(2),
            new Car(3),
            new Car(4)
          };
        for(Car myCar : myCars){
            myCar.drive();
            myCar.refuel();
            myCar.testEmissions();
        }
    }
}