java - Using superclass method to calculate price -

i doing problem on inheritance , hierarchy of classes. problem this: have superclass contains quantity attribute. code class here:

class items {  private int quantity;   public items(int quantity) {    this.quantity = quantity;  } 

then have 2 subclasses contains prices , other attributes. code snippet:

class coffee extends items {  private string size;   public coffee (int quantity, string size) {   super(quantity);   this.size = size;   } }  class donuts extends items {  private double price;  private string flavour;   public donuts(int quantity, double price, string flavour) {    super(quantity);    this.price = price;    this.flavour = flavour;   } } 

what want calculate total price each object.

my program reads text file , creates object , stores them in arraylist. text file reading this, please note have commented first 2 lines explain each token is, not included in real file.:

coffee,3,medium // name of item quantity , size

donut,7,0.89,chocolate // name quantity price flavor

donut,3,1.19,eclair

coffee,1,large

i want calculate total price without duplication of code. have done far in superclass this:

 public double totalprice(items x) {    double total = 0;    if(x instanceof coffee) {      total = getquantity() * getsizeprice();    } else {      if (x instanceof donuts) {        total = totalprice();       }     }    return total;  }    public abstract string getsizeprice(); 

in coffee subclass:

public double getsizeprice() {   double pricesmall = 1.39;   double pricemed = 1.69;   double pricelar = 1.99;    if(size == "small") {      return pricesmall;   } else {    if (size == "medium" ) {      return pricemed;     }   }   return pricelar; } 

i believe going in circles 1 wondering if community guide me in right direction. if question confusing, feel free ask , explain further. possible totalprice() method in each class , through ploymorphism class calculates price of items in main method.