ArrayList Problem

[Chris G Johnson]

Hi, I have a problem with the code below:-

import java.util.*;         //Needed when we use ArrayList
/**
 * Order class.
 * 
 * @author Ian Martin 
 * @version 14.9.4
 */
public class Order
{
    private ArrayList Orders;     //Will store references to Reservation objects
    
//Constructor 
    public Order()
    {
        Orders = new ArrayList(); //create an ArrayList object
    }
    
//Add a Order to the Order queue
    public void addOrders(item i)
    {
        Orders.add(i);
    }
    
//toString
    public String  toString()
    {
        String s = "\nItems on this Order are : \n";      //We'll build up a String with info on all the items in this order
        Order o;      //Used to store a reference to the order object that we retrieve from the ArrayList
        
        for (int i = 0; i < Orders.size();i++) //loop thru the ArrayList
        {
            o = (Order)Orders.get(i);   //get next object reference from the ArrayList
                                                    //and cast it to a Reservation reference
            s += o;     //Add data on this Reservation to the String s
                        //This uses the toString method in the Reservation class
        }
        return s;       //Pass back the String s as the method result
    }
    
//Calculate Booking cost
    public int  calcOrderCost(foodCollection fc)
    {
       int orderCost = 0; //Used to add up total
       Order o; 
       for (int i = 0; i < Orders.size();i++) //Loop and process each Reservation
        {
           o = (Order)Orders.get(i);    //get reference to next Reservation object
           orderCost += o.calcOrderCost(fc);  //get Reservation cost and add it to the total
        }
        return orderCost; //return the total cost of the booking
    }
}

The public string toString() method doesn't work and produces a class cast exception: null, Ithink this is because the arrayList is empty but I can't figure out why it is empty.

Thanks in advance to anyone who can shed some light onto this problem.

[Barry Higgins]

Don't think you're problem is with the ArrayList not being populated .. the hint is in the exception ClassCastException. This means that the object you are trying to cast to is not of that type.
When you call your addOrders method you pass it an object of type item and add that to the ArrayList but when you call toString or calcOrderCost you cast the items you take off the ArrayList to Order.
You might also want to have a look at the Collections tutorial on java.sun.com it's considered better practice to iterate through your ArrayList using the Collection methods than the way you have.
Anyway hope that helps..