当输入超出范围时使用do-while循环发送错误消息

Question

在这里，我使用 do while 循环来执行一个程序，该程序允许用户在一个数组中对学生的分数进行评分，然后将它们打印出来。 我正在努力实现一个系统，该系统在用户输入低于 0 或高于 100 的数字时发送错误消息，然后让用户重试。

导入 java.util.Scanner；

公共 class storeScore {

    public static void main(String [] args) {
   
        Scanner input = new Scanner (System.in);

        int scores [] = new int [7];
        int numberOfStudents = 7;


        //User input all scores. For loop works by asking for user input until it reaches the number as input in numberOfStudents.
        do 
        {
        for(int i = 0; i<numberOfStudents; i++) {

            scores[i] = input.nextInt();
           
            if (i == 0) {
                System.out.print("Enter the score for the 1st student: ");
            }
            else if (i == 1) {
                System.out.print("Enter the score for the 2nd student: ");
            }
            else if (i == 2) {
                System.out.print("Enter the score for the 3rd student: ");
            }
            else if (i >= 3) {
                System.out.print("Enter the score for the " + (i+1) + "th student: ");
            }
           
        } 
        
        //Error output if input is incorrect
        }          
        while (scores[i] < 0 || scores[i] > 100) {

            System.out.println("Input out of bounds. Score can only be between 0 and 100");

        }

      //Printing all scores.
        System.out.println("Thank you for your input. Your entered scores are: ");

        for (int i=0; i<numberOfStudents; i++)  
                {  
                    System.out.print(scores[i] + ", ");  
                }  
       
    
 input.close();
       
   
    }
   

}

Answer 1

您在 while 循环中打印错误消息，而没有任何方法可以打破该循环。

首先尝试将用户的输入捕获为一个 int 变量，您可以在将其分配给 score[] 之前检查它是否有效。

for(int i = 0; i<numberOfStudents; i++) {
        String message;
       
        if (i == 0) {
            message = "Enter the score for the 1st student: ";
        }
        else if (i == 1) {
            message = "Enter the score for the 2nd student: ";
        }
        else if (i == 2) {
            message = "Enter the score for the 3rd student: ";
        }
        else if (i >= 3) {
            message = "Enter the score for the " + (i + 1) + " student: ";
        }

        System.out.println(message);

        int score = input.nextInt();
        
        //Now check if the input value is valid
        while (score < 0 || score > 100) {
            System.out.println("Input out of bounds. Score can only be between 0 and 100");

            System.out.println(message);
   
            score = input.nextInt();
        }

        score[i] = score;
    } 

现在，循环将为学生 i 打印消息，然后输入分数。 如果分数无效，while 循环将打印出错误消息，并重新输入。 如果这次输入有效，while 循环会中断并将新分数分配给学生 i，否则它会重新打印错误消息并再次接受输入。