如何使用while while循環添加輸出？

Question

我需要添加飲料的所有費用，直到輸入5才能退出程序。我該如何去做呢？當我運行這個程序時，它只顯示最後一個訂單的總數，而不是全部訂單。

import java.util.Scanner; 

public class Beverage 
{ 
    // Constants 
    static final double COSTOFCOFFEE = 1.00; 
    static final double COSTOFTEA = .75; 
    static final double COSTOFCHOCOLATE = 1.25; 
    static final double COSTOFCAPPUCCINO = 2.25; 
    static final double tax = 0.06; 

    public static void main(String[] args) 
    // This method determines the type & amount of beverages desired 
    { 
    Scanner keyboard=new Scanner(System.in); 
    double cost = 0;   // cost of the beverages 
    int numberOfCups = 0;  // number of cups desired 
    int bevType;    // type of beverage selected 
    double totalcost = 0 ; 
    do 
    { 
     System.out.println("Hot Beverage Menu"); 
     System.out.println("Please select a choice from the following"); 
     System.out.println("1: Coffee"); 
     System.out.println("2: Tea"); 
     System.out.println("3: Hot Chocolate"); 
     System.out.println("4: Cappuccino"); 
     System.out.println("5: EXIT "); 
     bevType = keyboard.nextInt(); 
     if (bevType < 5 && bevType > 0) 
     { 
     System.out.println("How many cups would you like?"); 
     numberOfCups = keyboard.nextInt(); 
     } 
     switch(bevType) 
     { 
     case 1 : cost = numberOfCups * COSTOFCOFFEE; 
      break; 
     case 2 : cost = numberOfCups * COSTOFTEA; 
      break; 
     case 3 : cost = numberOfCups* COSTOFCHOCOLATE; 
      break; 
     case 4 : cost = numberOfCups * COSTOFCAPPUCCINO;  
      break; 
     case 5 : System.out.println("Thanks for your order"); 
      totalcost = totalcost + cost; 
      break; 
     default : System.out.println("Invalid Selection");   
     }  
     if (bevType == 1 || bevType == 2 || bevType == 3 || bevType == 4) 
     System.out.printf("The total cost is $%.2f \n" , cost); 
    }while (bevType!=5); 
    if(bevType == 5) 
     System.out.println("The total cost of all beverages is " +totalcost); 
    keyboard.close(); 
    } 
} 

Answer 1

將每個cost加到totalcost。喜歡的東西，

if (bevType == 1 || bevType == 2 || bevType == 3 || bevType == 4) 
    System.out.printf("The total cost is $%.2f \n" , cost); 
    totalcost += cost; //<-- add to total. 
} 

Answer 2

它只是顯示你的最後一個值的原因是因爲你沒有保持跟蹤它重新分配你的「成本」變量。在你的交換機中，你說：

cost = numberOfCups * X //where X is whatever type of coffee 

下一次有人選擇了不是5的東西時，通過說成本=來損失成本的價值。

有兩種方法可以解決這個問題。首先是使用一個公式，使成本在整個過程中保持其價值。這說

cost = cost + (numberOfCups) * X 

然而，混淆的「成本」一詞，因爲我們是在談論該項目的成本，而不是總成本來完成。但是，您已經有了一個可以跟蹤「totalCost」總成本的變量。

所以裏面的，如果你的開關後聲明中，你可以添加

totalCost = totalCost + cost; 

，或者使用更清潔的方式來寫它;

totalCost += cost; 

Answer 3

刪除行「totalcost = totalcost + cost;」在案例5和

加上「totalcost + = cost;」如果條件下

case 5 : System.out.println("Thanks for your order"); 
      // totalcost = totalcost + cost; <-----remove this line 
      break; 

default : System.out.println("Invalid Selection");   
}  

if (bevType == 1 || bevType == 2 || bevType == 3 || bevType == 4) 
{ System.out.printf("The total cost is $%.2f \n" , cost); 
    totalcost += cost; 
}