Java creating objects within objects

Question

I'm trying to create a Pizza menu. I have 3 classes,

PizzaBase (with get / set methods for the thickness of the base [either thin or deeppan])
PizzaTopping, again with get / set methods for the type of topping
Pizza, where my cost variable is stored and used across the 3 classes using inheritance.

As a cost variable is used for the base, the topping and the overall pizza itself.

Now my question is this, how would I go about creating a Pizza object, which in turn creates 1 base object, and a few toppings objects, each with a price?

I can work out how to calculate an overall price, I'm just a bit stuck creating objects within objects.

 public class PizzaTopping extends Pizza{

private String topping;




public String getTopping(){
    return this.topping; 
}

public void setTopping( String topping ){
    this.topping = topping;

    }

}



   public class PizzaBase extends Pizza{

  private String base;  


    public void setBase( String base ){
    this.base = base;
    }

    public String getBase(){
        return this.base;
    }




 }




 public class Pizza {
private double cost;

public void setCost( double cost ){
    this.cost = Math.abs(cost);
}
public double getCost(){
    return this.cost; 
}


public void makingPizza(){
    PizzaBase b = new PizzaBase();



}

 }

Why should PizzaTopping extend Pizza? A Pizza is composed of PizzaToppings; a PizzaTopping is not a Pizza itself. I would rethink the object model. — Vivin Paliath
– Vivin Paliath, Commented Dec 11, 2013 at 17:03
Yea since asking this question I have got rid of the inheritance aspect.. each class now has its own cost property. However I'm still struggling with creating objects within objects — Ryan H
– Ryan H, Commented Dec 11, 2013 at 17:08
Well you already have an object within an object, String topping. It's not really any more special than that. — kviiri
– kviiri, Commented Dec 11, 2013 at 17:13
I would make an interface for your "pricing" to start. This way, you can use polymorphism and impress your teacher. Second, I don't see any contructors, just getters/setters. I would have a constructor on Pizza that took an array/list of PizzaTopings and a PizzaBase. This constructor would then set all the approriate items on itself (encapsulation, teachers love that too). The PizzaToppings and PizzaBase classes probably also need some sort of constructor as well. — CodeChimp
– CodeChimp, Commented Dec 11, 2013 at 17:16

faisal · Accepted Answer · 2013-12-11 17:20:38Z

1

Replace the Pizza class with CostableItem class:

public class CostableItem {
 private double cost;

 public void setCost( double cost ){
    this.cost = Math.abs(cost);
 }
 public double getCost(){
    return this.cost; 
 }
}

Then extend it in both toppings and base:

public class PizzaBase extends CostableItem {...}
public class PizzaTopping extends CostableItem {...}

After that create a class called Pizza that has one base and multiple toppings:

public class Pizza{
 private PizzaBase base;
 private ArrayList<PizzaToppings> toppings;
 //..
}

answered Dec 11, 2013 at 17:20

faisal

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2 Comments

Vivin Paliath Over a year ago

It would be better to make CostableItem an interface.

faisal Over a year ago

I think so too, just answering his question about how to create a object inside a object.

Vivin Paliath · Accepted Answer · 2013-12-11 17:25:50Z

You don't need inheritance for this at all. At the most you might need an interface. So I would design it this way:

public interface PricedItem {
   double getCost(); //double is suitable for our purposes
}

Since you want to calculate cost, everything that is a priced item should have a getCost() method. This will apply to your PizzaTopping, PizzaBase, and Pizza class:

public class PizzaTopping implements PricedItem

    private String name;
    private double cost;

    public PizzaTopping(String name, double cost) {
        this.name = name;
        this.cost = cost;
    }

    ...

    @Override
    public double getCost() {
        return cost;
    }
}

More or less the same thing for PizzaBase:

public class PizzaBase implements PricedItem {

    private double cost;

    ...

}

Your Pizza class will also implement PricedItem. But what is also important is that you will have a collection of PizzaTopping instances; there is no inheritance here!

public class Pizza implements PricedItem {

   private double cost;
   private PizzaBase base;
   private List<PizzaTopping> toppings;

   public Pizza(double cost, PizzaBase base) {
        this.cost = cost;
        this.base = base;
        toppings = new ArrayList<PizzaTopping>();
   }

   ...

   public void addTopping(PizzaTopping topping) {
       //left as an exercise to the reader :)
   }

   @Override
   public double getCost() {
        //this is left as an exercise to the reader :)

        return totalCost;
   }  
}

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