Online Car Ordering in Java

Car shopping these days has never been easier; if you're looking for a new car, the manufacturer website will usually feature a customization app on their website that will allow you to see what cool things you can equip your car with out of the box. While you can go into a website and customize what you'd like from scratch, they'll usually provide a few starter packages to make your experience a little smoother. This is something we can capture in our code using the Prototype Pattern!

The CarPackage and SportsCar:

public interface CarPackage
{
   CarPackage Clone();
}

// Car Implementation:
public class SportsCarPackage implements CarPackage
{
   public String seatType;
   public String engineModel;
   public boolean hasSunRoof;

   public SportsCarPackage()
   {
       this.seatType = "Basic";
       this.engineModel = "V6";
       this.hasSunRoof = false;
   }

   public CarPackage Clone()
   {
       SportsCarPackage copy = new SportsCarPackage();
       copy.seatType = this.seatType;
       copy.engineModel = this.engineModel;
       copy.hasSunRoof = this.hasSunRoof;
       return copy;
   }
}

The Car Catalogue:

With the implementation of our sports car package, we can create a cache where we'll store the prototypes.

public class CarCatalogue
{
   protected HashMap<String, CarPackage> catalogue;

   public CarCatalogue()
   {
       this.catalogue = new HashMap<String, CarPackage>();
   }

   public void Add(String key, CarPackage prototype)
   {
       this.catalogue.put(key, prototype.Clone());
   }

   public CarPackage Get(String key)
   {
       if(this.catalogue.containsKey(key))
       {
           return this.catalogue.get(key).Clone();
       }
       else
       {
           throw new IllegalArgumentException("Key does not exist.");
       }
   }
}

Demo of the Prototype Pattern:

public class Solution
{
   public static void main(String[] args)
   {
       CarCatalogue catalogue = new CarCatalogue();

       // Create a basic package with default values:
       SportsCarPackage basicPackage = new SportsCarPackage();
       catalogue.Add("Basic", basicPackage);

       // Create the next level up:
       SportsCarPackage trackPackage = new SportsCarPackage();
       trackPackage.seatType = "Leather";
       trackPackage.hasSunRoof = true;
       
       catalogue.Add("Track", trackPackage);

       // Add the sporty option:
       // Base it off of the Track package:
       SportsCarPackage sportPackage = (SportsCarPackage)catalogue.Get("Track");
       sportPackage.engineModel = "V8";

       catalogue.Add("Sport", sportPackage);

       // Create a custom package:
       SportsCarPackage myCustomPackage = (SportsCarPackage)catalogue.Get("Sport");
       // Extra power:
       myCustomPackage.engineModel = "V8 Hemi";
       // But no sun roof :(
       myCustomPackage.hasSunRoof = false;
   }
}