package chapter3.demo31; public class Order { private final String orderId; private final OrderItem[] items; private double total; // 有参构造 public Order(String orderId) { this.orderId = orderId; this.items = new OrderItem[3]; } // 获取订单号 public String getOrderId() { return orderId; } // 获取订单列表 public OrderItem[] getItems() { return items; } // 获取订单总额 public double getTotal() { calTotal(); return total; } // 指定一个订单项 public void setItem(OrderItem item, int i) { this.items[i] = item; } // 计算订单总额 public void calTotal() { double total = 0; for (OrderItem item : items) { total += item.getNum() * item.getBook().getPrice(); } this.total = total; } }