當我將商品添加到購物車時出現錯誤的雜貨商品

Question

這是用於我的課堂作業。我一直在輸出中收到錯誤的groceryitem。代碼運行時我應該如何獲得正確的項目？

這裏是輸出目前我得到：

購物名稱：加里

---

冰淇淋：5個單位在$ 4.25每單位= $ 21.25

冰淇淋：5個單位在$ 4.25 per unit = $ 21.25

---->小計= $ 42.5

- ---> 7％的稅= $ 2.975

---->共= $ 45.475

購物者名稱：薩利

---

冰淇淋：2個單位在每單位$ 4.25 = $ 8.5

冰淇淋：2個單位在每單位$ 4.25 = $ 8.5

---->小計= $ 17.0

----> 7％的稅= $ 1.1900000000000002

---->總= $ 18.19

---

車類：

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(""); 
} 
} 

驅動程序類：

/** 
* 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

這看起來錯：

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

您正在爲自己分配GroceryItem。

與addItem2方法相同。

其實，您的購物車似乎沒有任何方法來存儲物品。看起來你並沒有在這裏掌握要領。回到書籍恐怕....

Answer 2

你在addItem方法分配項目本身。聲明實例變量並通過使用this指定您正在分配給實例變量。

例如：

public class Cart { 
private GroceryItem groceryItem; 
... 

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

然後，當你打印結果，使用實例變量groceryItem。

另外，在java中，成員（變量/方法名稱）應該在lower camel case中。