我该如何让这个哨兵控制回路起作用？

Question

它一切都很好。但是当它到达结尾，并询问我是否想再试一次时，它只是终止程序，我不会输入y或n

编辑：对不起，我应该在发布前更好地检查预览，但似乎就像我在提交时搞砸了代码一样。这里是我的实际代码

import java.util.Scanner; 

class MillionDollarYears2 
{ 
public static void main(String[] args) 
{ 
    String answer = "y"; 
    double dollars; 
    final double interest = 0.05; 
    int year = 0; 
    Scanner scan = new Scanner(System.in); 

    while(answer.equals("y")) 
    { 
     System.out.println("How many dollars are deposited?"); 
     dollars = scan.nextDouble(); 


     while(dollars < 1000000.00) 
     { 
      dollars = dollars + dollars * interest; 
      year = year + 1; 
     } 
      System.out.println("It took " + year + " years to reach your goal."); 

      System.out.println("Would you like to try again? (y or n)"); 
      answer = scan.nextLine(); 


    } 

} 

}

Answer 1

您还没有进入Y/N回答正确的变量。 您的相关片段（含澄清评论）：

System.out.println("It took " + year + " years to reach your goal");            
answer = scan.nextLine(); // This seems like a mistake 

System.out.println("Would you like to try again? (y or n)"); 
dollars = scan.nextLine(); // This should be saved to answer, which the loop checks against 

因此，更正后，while循环的结束应该是这个样子：

System.out.println("It took " + year + " years to reach your goal");            

System.out.println("Would you like to try again? (y or n)"); 
answer = scan.nextLine(); 

Answer 2

它终止，因为在此之后行：

System.out.println("It took " + year + " years to reach your goal");            
answer = scan.nextLine(); 

答案可能包含一个不是“y”的值并终止while循环。

你问后再次尝试这样做：

dollars = scan.nextLine(); 

变化dollars到answer该行之前删除answer = scan.nextLine();两行。

Answer 3

变化scan.nextLine()到scan.next()

工作PROG：

public static void main(String[] args) 
{ 
    String answer = "y"; 
    double dollars; 
    final double interest = 0.05; 
    int year = 0; 
    Scanner scan = new Scanner(System.in); 

    while(answer.equals("y")) 
    { 
     System.out.println("How many dollars are deposited?"); 
     dollars = scan.nextDouble(); 


     while(dollars < 1000000.00) 
     { 
      dollars = dollars + dollars * interest; 
      year = year + 1; 
     } 
      System.out.println("It took " + year + " years to reach your goal."); 

      System.out.println("Would you like to try again? (y or n)"); 
      answer = scan.next(); 


    } 

}