如何使用方法从Map中返回值？

Question

如何在这种情况下返回int值？

import java.util.*; 

    public class ShoppingCart { 

    private Map<String, Purchase> shoppingCart = new HashMap<String, Purchase>(); 

    public void add (String product, int price) { 
     Purchase purchase = new Purchase(product, 1, price); 
     shoppingCart.put(product, purchase); 
    } 

    public int totalPrice() { 
     //How do I accomplish this? I want to return all the prices summed together 

     } 
    } 
} 

购买方式的构造是：

public Purchase(String product, int amount, int price) { 

Answer 1

通过在地图中的值（Javadoc）你循环。因为这很可能是功课，我会让你弄清楚其余的。

Answer 2

Iterate through map，总结每次购买

Answer 3

的你需要遍历映射值的价格总和的总价格

例如，这代码将工作。

public int totalPrice() { 
     int sum = 0; 
     for(Purchase p:shoppingCart.values()){ 
      sum+=p.getPrice(); 
     } 
     return sum; 
    } 

Answer 4

public int totalPrice() { 
    int i = 0; 
    for(Purchase purchase : shoppingCart.values()) { 
     i += purchase.getPrice(); 
    } 
    return i; 
} 

Answer 5

Map<String, Purchase> map = new HashMap<String, Purchase>(); 

    for(String value : map.values()) { 

    } 

Answer 6

在下面的代码，你并不需要为循环再次运行...
进口的java.util。*;

public class ShoppingCart { 

    private int sum = 0;  

    private Map<String, Purchase> shoppingCart = new HashMap<String, Purchase>(); 

    public void add (String product, int price) { 
     Purchase purchase = new Purchase(product, 1, price); 
     if(!shoppingCart.contains(product)){ 
      shoppingCart.put(product, purchase); 
      sum += price; 
     } 
    } 

    public int totalPrice() { 
     return price; 
     } 
    } 
}