无限循环或提前终止 do while 循环

Question

我已经和这个程序斗争了一段时间了。它已经开始正确编译，但是当我按原样运行它时，它会无限显示“你的账单是__”。当我更改初始响应值时，它拒绝运行。我不知道如何解决它。

/* Savannah Moore
   CSCI 1301
    2/11/2013
    Internet Package Code: Code determines customer's final pricing. */
import java.util.Scanner;

public class internet{
    public static void main(String[] args){
      double hours, price;
      int internet;
      String response, check="Yes";


      Scanner kb = new Scanner(System.in); /* This sections questions the user as to which package they have bought. */
       System.out.println("Our internet packages include:");
        System.out.println("Package 1: For $9.95 per month, 10 hours of access are provided. Additional hours are $2.00 per hour.");
        System.out.println("Package 2: For $13.95 per month, 20 hours of access are provided. Additional hours are $1.00 per hour.");
        System.out.println("Package 3: For $19.95 per month, unlimited access is provided.");
        System.out.println("Please enter your package number:");
       internet=kb.nextInt();
        System.out.println("Please enter your total hours used:");
       hours=kb.nextDouble();   
        response = "Yes";

while(check.compareToIgnoreCase(response)== 0)
  {
      switch (internet)
      {
      case 1: 
              {  if (hours > 10)
                       price = (hours-10)*2 + 9.95; /* This adds the additional hours to the user's price at the current overage rate. */
                    else    
                        price = 9.95;
                }
              System.out.println("Your bill is $" +price);  
               break; 
      case 2: 
              {  if (hours > 20)
                       price = (hours-20) + 13.95;
                    else    
                        price = 13.95;
                }
              System.out.println("Your bill is $" +price);  
               break;        
     case 3:System.out.println("Your bill is $19.95");  
                break; 
      default: System.out.println("This package choice is invalid.");

      System.out.println("Would you like to compare your price with that of another package? Yes or No"); /* This gives the user the ability to stop the loop. */
      response=kb.nextLine();
      response=kb.nextLine();   
     }
    }

    System.out.println("Thank you for using us as your internet service provider.  Have a nice day!");
    }
    }

Answer 1

循环进入无限循环，因为用户将响应更改为“否”的机会在 case 语句中。因此，当您 break; 退出 case 语句时，您会立即跳回 'while' 检查，并且因为 response 和 check 都仍然是 'Yes'，它会再次执行所有操作。

只需将这些语句放在 case 语句中的 default: 案例之后，它应该可以工作。

换句话说，改变：

   ...
   default: System.out.println("This package choice is invalid.");

   System.out.println("Would you like to compare your price with that of another package? 
       Yes or No"); /* This gives the user the ability to stop the loop. */
   response=kb.nextLine();
   response=kb.nextLine();   
  }
}

到：

     ...
     default: System.out.println("This package choice is invalid.");
   }
   System.out.println("Would you like to compare your price with that of another package? 
        Yes or No"); /* This gives the user the ability to stop the loop. */
   response=kb.nextLine();
   response=kb.nextLine();   
}

我不确定你为什么要两次response=kb.nextLine();。

Answer 2

这应该可以解决问题

import java.lang.*;
import java.util.Scanner;

public class Program
{
    /**
     * This is the main entry point for the application
     */
  public static void main(String[] args){
      double hours, price;
      int internet;
      String response, check="Yes";


        response = "Yes";

while(check.compareToIgnoreCase(response)== 0)
  {

      Scanner kb = new Scanner(System.in); /* This sections questions the user as to which package they have bought. */
       System.out.println("Our internet packages include:");
        System.out.println("Package 1: For $9.95 per month, 10 hours of access are provided. Additional hours are $2.00 per hour.");
        System.out.println("Package 2: For $13.95 per month, 20 hours of access are provided. Additional hours are $1.00 per hour.");
        System.out.println("Package 3: For $19.95 per month, unlimited access is provided.");
        System.out.println("Please enter your package number:");
       internet=kb.nextInt();
        System.out.println("Please enter your total hours used:");
       hours=kb.nextDouble();   
      switch (internet)
      {
      case 1: 
              {  if (hours > 10)
                       price = (hours-10)*2 + 9.95; /* This adds the additional hours to the user's price at the current overage rate. */
                    else    
                        price = 9.95;
                }
              System.out.println("Your bill is $" +price);  
               break; 
      case 2: 
              {  if (hours > 20)
                       price = (hours-20) + 13.95;
                    else    
                        price = 13.95;
                }
              System.out.println("Your bill is $" +price);  
               break;        
     case 3:System.out.println("Your bill is $19.95");  
                break; 
      default: System.out.println("This package choice is invalid.");
      }
      System.out.println("Would you like to compare your price with that of another package? Yes or No"); /* This gives the user the ability to stop the loop. */
      response=kb.nextLine();
      response=kb.nextLine();   

    }

    System.out.println("Thank you for using us as your internet service provider.  Have a nice day!");
    }
}