使用GroceryList的java建议

Question

我正在制作一个程序，我有一个名为GroceryItem的类，另一个名为GroceryList，第三个是运行程序的main方法

我在这个项目上做了很多，但我现在被卡住了。请看一下我的代码并帮助我

食品杂货类：

public class GroceryItem {



    private String name;  
    private double pricePerUnit;  
    private int quantity;  

    public GroceryItem(int quantity, String name, double pricePerUnit) {  

        this.name = name;  
        this.pricePerUnit = pricePerUnit;  
        this.quantity = quantity;  

    }  

    public double getCost() {  

        return (this.quantity * this.pricePerUnit);  
    }  

    public void setQuantity(int quantity) {  

        this.quantity = quantity;  

    }  

}  

---

杂货店类别：

public class GroceryList {



    private GroceryItem[] list = null;  
    int num;  

    public GroceryList() {  

        list = new GroceryItem[10];  
        this.num = 0;  

    }  

    // Constructs a new empty grocery list.  
    public void add(GroceryItem item) {  
        list.add(item);  

    }  

    // Adds the given item order to this list, if the list is not full (has  
    // fewer than 10 items).  
    public double getTotalCost() {  
        double totalcost = 0;  
        for(int i = 0; i < list.length; i++){  
        totalcost += getGroceryItemOrder(getCost());  
        }  

        return totalcost;  
    }  
    // Returns the total sum cost of all grocery item orders in this list.  
}  

---

主要方法：

public static void main(String[] args) {


    GroceryList list = new GroceryList();  
    GroceryItem carrots = new GroceryItem(5,"Carrots", 0.40);  
    list.add(carrots);  
    GroceryItem apples = new GroceryItem( 4,"Apples", 0.15);  
    list.add(apples);  
    GroceryItem rice = new GroceryItem( 1,"Rice", 1.10);  
    list.add(rice);  
    GroceryItem tortillas = new GroceryItem(10,"Tortillas", .05);  
    list.add(tortillas);  
    GroceryItem strawberries = new GroceryItem(1,"Strawberries", 4.99);  
    list.add(strawberries);  
    GroceryItem chicken = new GroceryItem( 1,"Chicken", 5.99);  
    list.add(chicken);  
    GroceryItem lettuce = new GroceryItem( 1,"Lettuce", 0.99);  
    list.add(lettuce);  
    GroceryItem milk = new GroceryItem( 2,"Milk", 2.39);  
    list.add(milk);  
    GroceryItem yogurt = new GroceryItem( 3,"Yogurt", 0.60);  
    list.add(yogurt);  
    GroceryItem chocolate = new GroceryItem(1,"Chocolate", 3.99);  
    list.add(chocolate);  

}  

}

Answer 1

用这个来添加你的购物元素

杂货店类

public class GroceryList {



List<GroceryItem> list = null;  
int num;  

public GroceryList() {  

    list = new ArrayList<GroceryItem>();  
    this.num = 0;  

}  

// Constructs a new empty grocery list.  

   public void add(GroceryItem item) {  
    list.add(item);  
   System.out.println("Added Grocery :::: >>>> NAME:" +item.getName()+ " :::::  PRICE PER UNIT: "+item.getPricePerUnit()+" :::::: QUANTITY: "+item.getQuantity()+" ::::: FINALCOST: "+(item.getQuantity()*item.getPricePerUnit()) );}


// Adds the given item order to this list, if the list is not full (has  
// fewer than 10 items).  
 public double getTotalCost() {  
    double totalcost = 0;  
    for(int i = 0; i < list.size(); i++){  
    totalcost += list.get(i).getCost();  
    }  

    return totalcost;  
}  
// Returns the total sum cost of all grocery item orders in this list.  
}  


    /// Add this function as toString class

    @Override
        public String toString() {
            return "GroceryList [list=" + list + ", num=" + num + "]";
        }

---

// add a function for finding cost per item like this

public HashMap<String,Double>  getCostPerItem(int i) {
           HashMap<String, Double> itemPriceName= new HashMap<String, Double>();
           itemPriceName.put(list.get(i).getName(), 
              (list.get(i).getPricePerUnit()*list.get(i).getQuantity()));
          return itemPriceName;
       }

---

//在main函数中，可以调用上述指定函数

for(int i=0;i<list.list.size();i++) {
            System.out.println("Cost Per Item  "+list.getCostPerItem(i));
        }

---

Answer 2

您正在尝试使用add方法向数组中添加内容。 您应该使用ArrayList或类似的数据结构，或者使用索引添加项：

list[ index++ ] = item

原因是简单数组没有add方法ArrayList和其他几个集合类都可以

此外，在原始代码中，您有以下行：

totalcost += getGroceryItemOrder(getCost());  

此代码中没有定义方法getGroceryItemOrder(...)。在这种形式中，它将在GroceryItemList类上调用getCost()GroceryItemList没有这样的方法，因此会出现错误
您想在当前列表项上调用getCost()，因此需要的行是：

totalcost += list[i].getCost();