循環不承認一個不斷變化的變量

Question

我想詢問用戶是否要繼續輸入號碼添加到了總價值

int total=0; 

    char letter='y'; 

    while (letter == 'y'); 
    { 
      Scanner userInput = new Scanner (System.in); 
      System.out.println("Input your number"); 
      int number = userInput.nextInt(); 

      total=number+total; 


      Scanner userInput1 = new Scanner (System.in); 
      System.out.println("Would you like to continue? Input y/n"); 
      char letter = userInput1.next().charAt(0); //**This is where there is an error** 

    }   
    System.out.println("The total of all the numbers inputted is "+total); 
    } 
} 

Answer 1

1. 你不應該有;第5行（while一行）。
2. 在循環之外初始化Scanner只有一次性能更高性能。
3. 在循環的最後一行，使用letter = ***而不是char letter = ***。您已經聲明變量letter。
4. 也許你應該處理nextInt行，以防用戶鍵入非數字。

可能的改進：

int total=0; 
char letter='y'; 
Scanner userInput = new Scanner(System.in); 
while(letter == 'y') 
{ 
    System.out.println("Input your number"); 
    int number = userInput.nextInt(); 
    total += number; 
    System.out.println("Woud you like to continue? Input y/n"); 
    letter = userInput.next().charAt(0); 
} 

Answer 2

只需刪除char，因爲letter已經定義。取而代之的

char letter = userInput1.next().charAt(0); 

寫

// char removed 
letter = userInput1.next().charAt(0); 

同時也可作爲Pemap表示刪除;的while

後，基本上你的代碼應該是類似於以下

while (letter == 'y') { 
     Scanner userInput = new Scanner (System.in); 
     System.out.println("Input your number"); 
     int number = userInput.nextInt(); 

     total = number + total; 


     Scanner userInput1 = new Scanner(System.in); 
     System.out.println("Would you like to continue? Input y/n"); 
     letter = userInput1.next().charAt(0); 
}   

Answer 3

2個問題。 1）你有一個;在一段時間聲明行中。第二）你已經聲明瞭字母變量。第二次詢問輸入後無需重新申報。希望能幫助到你。

int total=0; 
char letter='y'; 
while (letter == 'y') 
{ 
     Scanner userInput = new Scanner (System.in); 
     System.out.println("Input your number"); 
     int number = userInput.nextInt(); 

     total=number+total; 


     Scanner userInput1 = new Scanner (System.in); 
     System.out.println("Would you like to continue? Input y/n"); 
     letter = userInput1.next().charAt(0); //**This is where there is an error** 
}   
System.out.println("The total of all the numbers inputted is "+total); 
} 
}