修改项目目录

src/chapter3/demo31/Order.java

@@ -0,0 +1,43 @@
+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;
+    }
+}