从数组列表中返回某个“类型”的对象

Question

I have an order class:

public abstract class Order {
protected String location;
protected double price;

public Order(double price, String location){
    this.price = price;
    this.location = location;
}
public abstract double calculateBill();

public String getLocation() {
    return location;
}
public double getPrice() {
    return price;
}
public abstract String printOrder(String format);       
}

It is extended by three subclasses 'NonProfitOrder', 'RegularOrder', and 'OverseasOrder' each of which only differ in the way they calculateBill().

Then I have and OrderManger class

public class OrderManager {
private ArrayList<Order> orders;

public OrderManager() {

}
public OrderManager(ArrayList<Order> orders) {
    this.orders = orders;   
}   
public void addOrder(Order o) {
    orders.add(o);
}   
public ArrayList<Order> getOrdersAbove(double val) {
    for (Order o : orders) {
        double bill = o.calculateBill();
        if (bill > val)
            orders.add(o);
    }
    return orders;
}   
public int numOrders() {
    return orders.size();
}   
public String printOrders() {
    for (Order o : orders){
        String format = "Long";
    }
    return printOrders("Long");
}
public String printOrders(String type) {
    for (Order o : orders) {

    }       
}
public double totalBill() {
    double sum = 0;
    for(Order o : orders) {
         sum = o.calculateBill();
    }
    return sum;     
}   
}

I believe that i have everything working correctly, except that I am having trouble with the printOrders(String type) which return a string of all orders of 'type' where 'type' is "Regular", "Overseas", or "NonProfit". My question would be what is the correct way to loop through and array list and only returning the objects of a given 'type'?

Answer 1

Simple solution here would be the following:

public String printOrders(Class orderClass) {
    StringBuilder sb = new StringBuilder();
    for (Order o : orders) {
        if(o.getClass().equals(orderClass))
        {
            sb.append(o.printOrder()).append("\n");
        }
    }
    return sb.toString();       
}

Then when you call the method:

String orderString = orderManager.printOrders(NonProfitOrder.class);
System.out.println(orderString);