当我将商品添加到购物车时错误的杂货商品

Question

这是我的课堂作业。我一直在输出中得到错误的杂货。运行代码时我应该如何获取正确的项目？

这是我目前得到的输出：

购物者姓名：Gary

---

冰淇淋：5 件，每件 4.25 美元 = 21.25 美元

冰淇淋：5 件，每件 4.25 美元 = 21.25 美元

----> 小计 = $42.5

----> 7% 税 = 2.975 美元

---->总计 = $45.475

购物者姓名：Sally

---

冰淇淋：2 件，每件 4.25 美元 = 8.5 美元

冰淇淋：2 件，每件 4.25 美元 = 8.5 美元

----> 小计 = $17.0

----> 7% 税 = 1.1900000000000002 美元

---->总计 = $18.19

---

购物车类：

public class Cart
{
public String Name;
public int ItemNum;
public double tax;




public Cart(String ShopperName){
    Name = ShopperName;
}
public String getShopperName(){
    return Name;
}
public int getItemNumber(){
    return ItemNum;
}
public void addItem1(GroceryItem GroceryItem, int NumberItem){
    GroceryItem = GroceryItem;
    ItemNum = NumberItem;
}
public void addItem2(GroceryItem GroceryItem, int NumberItem){
    GroceryItem = GroceryItem;
    ItemNum = NumberItem;
}
public double getItemTotal(){
    double item_total = (double) (GroceryItem.getCost()*getItemNumber());
    return item_total;
}
public double getSubtotal(){
    double subtotal = (double) (getItemTotal() + getItemTotal());
    return subtotal;
}
public double getTaxTotal(){
    double tax = .07;
    double taxtotal = (double) (getSubtotal()*tax);
    return taxtotal;
}
public double getTotal(){
    double Total = (double) (getTaxTotal()+getSubtotal());
    return Total;
}
public void printReceipt(){
    System.out.println("Shopper Name: " + getShopperName());
    System.out.println("----------------------");
    System.out.println(GroceryItem.getName()+":"+ getItemNumber()+ " units at $" + GroceryItem.getCost()+" per unit"+ " = $"+ getItemTotal());
    System.out.println(GroceryItem.getName()+":"+ getItemNumber()+ " units at $" + GroceryItem.getCost()+" per unit"+ " = $"+ getItemTotal());
    System.out.println("----> Subtotal = $" + getSubtotal());
    System.out.println("----> 7% tax = $" + getTaxTotal() );
    System.out.println("---->Total = $" + getTotal());
    System.out.println("");
    System.out.println("");
    System.out.println("");
}
}

驱动类：

/**
 * Driver for Cart and GroceryItem.
 */
public class Driver
{
public static void main(String[] args)
{
    // create grocery items
    GroceryItem item1 = new GroceryItem("milk", 3.39);
    GroceryItem item2 = new GroceryItem("eggs", 1.75);
    GroceryItem item3 = new GroceryItem("ice cream", 4.25);

    // create new carts
    Cart shopper1 = new Cart("Gary");
    Cart shopper2 = new Cart("Sally");


    // add items to first cart 
    shopper1.addItem1(item2, 1);        //1 "eggs" is being added
    shopper1.addItem2(item1, 5);        //5 "milk" are being added

    // add items to second cart
    shopper2.addItem1(item3, 2);        //2 "ice cream" are being added
    shopper2.addItem2(item2, 2);        //2 "eggs" are being added

    // print cart's receipt
    shopper1.printReceipt();
    shopper2.printReceipt(); 

}
}

Answer 1

这看起来不对：

public void addItem1(GroceryItem GroceryItem, int NumberItem){
    GroceryItem = GroceryItem;
    ItemNum = NumberItem;
}

您正在将 GroceryItem 分配给它自己。

addItem2 方法也是如此。

实际上，您的购物车似乎没有任何存储物品的方法。看起来你没有掌握这里的要点。回到书本上，恐怕……

Answer 2

您在 addItem 方法中将项目分配给自身。声明实例变量并使用this 指定您要分配给实例变量。

例如：

public class Cart {
private GroceryItem groceryItem;
...

public void addItem1(GroceryItem groceryItem, int NumberItem){
    this.groceryItem = groceryItem;
    ...

然后在打印结果时，使用实例变量groceryItem。

另外，在java 中，成员（变量/方法名称）应该在lower camel case 中。