Java arraylist add the qty

I am having an issue with comparing the properties of myProduct.setRefno(product.getRefno()), imported from another class along with a description, price and qty. I need to be able to key in a refno and if the reference number exists in the basket container, then I add only the qty rather than all the item details:

Actualmente el programa funciona de la siguiente manera:

ref1 description1 price1 1(qty)
ref2 description2 price2 1(qty)
ref1 description1 price1 1(qty)

Sin embargo, me gustaría como:

ref1 description1 price1 2(qty)
ref2 description2 price2 1(qty)

Si es el mismo refno, agrega solo la cantidad.

public class Zapper {

    public static void main(String[] args) throws ItemException {
        System.out.println("\n\nThis is Purchases\n\n");

        Products stock=new Products();// Define Variable 
        Products basket=new Products();// Define Variable 
        Purchase product;
        String refno;
        int offer;
        int count;
        int grandtotal;         
        char option;//char variable option

        boolean finished=false;//variable "boolean" set 

        while (!finished) { 
            try {
                option=Console.askOption("\n A)dd P)rint R)emove Q)uit");
                stock.open("stock.lin");
                switch (option) {   
                    case 'A': 
                        product= new Purchase();
                        refno= Console.askString("Enter Ref No:..");
                        product=(Purchase)stock.find(refno);//cast operator 
                        if ( product == null) {
                            System.out.println("Cannot find Ref No");
                        } else {
                            product.print("");
                            Purchase myProduct = new Purchase();
                            myProduct.setRefno(product.getRefno());
                            myProduct.setDescription(product.getDescription());
                            myProduct.setPrice(product.getPrice());
                            myProduct.setQty(1);
                            myProduct.setOffer(product.getOffer());
                            basket.add(myProduct);//add the value of item into Container stock  
                        }
                        break;//end of case statement Add

                    case 'R': 
                        refno= Console.askString("Enter Ref No:..");
                        Product myProduct = new Product();
                        myProduct=(Purchase)basket.find(refno);//cast operator
                        myProduct.setQty(1);
                        if ( myProduct == null)
                            System.out.println("Cannot find Ref No");

                        else {
                            basket.remove(myProduct);
                            basket.print("");   
                        }
                        break;//end of case statement Find

                    case 'P': 
                        basket.print("\nYou have purchased...");
                        break;//end of case statement Print             
                    case 'Q': 
                        finished=true;
                        break;//end of case statement "Q" 
                    case '\0':/*Do Nothing*/
                        break;//end of case statement "Do Nothing"
                    default:    
                        System.out.println("Error: Invalid Option ");
                        break;//end of case statement default
                }
            } catch (ItemException e) {
                System.out.println(e.getMessage());
            } catch (IOException e) {
                System.out.println(e.getMessage());
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }   
        }
        System.out.println("\n\nPurchases Finished \n\n");
    }

}

Solo tiene que cambiar el addmétodo-en su Productsclase. PurchaseSupongamos que almacena sus objetos en una Lista en su Productclase, podría verse así:

private List<Purchase> products; 

public void add(Purchase product) {
    String refNo = product.getRefno();
    for (Purchase p : this.products) { //for every product
        if (p.getRefno().equals(refNo)) { //if two refNumbers equals
            p.setQty(p.getQty() + product.getQty()); //add the desired quantity
            return; //force method to abort
        }
    }
    this.products.add(product); //otherwise, add the new product
}

Aunque, tengo que decir que encuentro algunos de tus nombres de clase un poco inusuales. Recuerde que siempre deben dar una buena pista sobre lo que realmente representan, por ejemplo, su Purchaseclase se parece más a Product. :)