如何在例外發生后創建一個for回圈再次向用戶詢問相同的輸入？

所以澄清一下，當程式要求用戶輸入數字 1 時：如果用戶要輸入一個字母，我需要程式告訴用戶輸入不匹配，然后再次要求用戶輸入數字 1。這需要僅使用一個 for 回圈來實作，并且不能有影響總和或平均值的負數。這是我到目前為止所擁有的：

import java.util.*;
import java.text.*;

class fivePositiveNumbers{
   public static void main(String[] args){
      Scanner keyboard = new Scanner(System.in);
      int userNumber;
      int sum = 0;
      System.out.println("This program will give the sum and average of 5 positive integers,");
      
      for(int i = 1; i <= 5; i  ){
         System.out.println("Enter number "   i   ": ");
         try{
            userNumber = keyboard.nextInt();
            sum = sum   userNumber;
            if(userNumber <= 0){
               throw new Exception("The integer must be positive.");
            }
         } catch(InputMismatchException e){
               System.out.println("This data type is incorrect.");
               keyboard.nextLine();
         } catch(Exception e){
               System.out.println(e.getMessage());
               keyboard.nextLine();
         }
      }
      System.out.println("The sum is "   sum   " and the average of your 5 numbers is "   sum / 5   ".");
   }
}

uj5u.com熱心網友回復：

僅當提供有效輸入時，才使用將增加回圈計數的回圈while。for無論輸入的有效性如何，您的解決方案都會自動增加回圈計數器。

int i = 1;

while (i <= 5) {

    System.out.println("Enter number "   i   ": ");
        try{
            userNumber = keyboard.nextInt();
            if(userNumber <= 0){
                throw new Exception("The integer must be positive.");
            }
            sum = sum   userNumber; // this belongs after the negative check
            i  ; // increment the count after all validations are successfully completed
        } catch(InputMismatchException e){
            System.out.println("This data type is incorrect.");
            keyboard.nextLine();
        } catch(Exception e){
            System.out.println(e.getMessage());
            keyboard.nextLine();
        }
    }
}

如果您選擇使用for回圈，請從回圈宣告中洗掉計數器增量

for (int i = 1; i <= 5;) {
    // your logic and exception handling here
    i  ; // as in the while, increment only after all validations are successfully completed
}

還有一點......如果數字為負，我認為沒有必要拋出例外。我認為最好簡單地執行 acontinue以避免增加回圈計數器。這是這樣做的結果：

This program will give the sum and average of 5 positive integers,
Enter number 1: 
-5
The integer must be positive.
Enter number 1: 
-2
The integer must be positive.
Enter number 1: 
-3
The integer must be positive.
Enter number 1: 
-4
The integer must be positive.
Enter number 1: 
-5
The integer must be positive.
Enter number 1: 
1
Enter number 2: 
2
Enter number 3: 
3
Enter number 4: 
5
Enter number 5: 
4
The sum is 15 and the average of your 5 numbers is 3.

如您所見，我輸入了幾個負數，程式繼續運行，回圈計數器沒有增加。完整的解決方案continue：

public static void main(String[] args) {
      Scanner keyboard = new Scanner(System.in);
      int userNumber;
      int sum = 0;
      System.out.println("This program will give the sum and average of 5 positive integers,");
          
      for(int i = 1; i <= 5; ){
         System.out.println("Enter number "   i   ": ");
         try{
            userNumber = keyboard.nextInt();
            if(userNumber <= 0){
               System.err.println("The integer must be positive.");
               continue;
            }
            sum = sum   userNumber;
            i  ;
         } catch(InputMismatchException e){
               System.out.println("This data type is incorrect.");
               keyboard.nextLine();
         } catch(Exception e){
               System.out.println(e.getMessage());
               keyboard.nextLine();
         }
      }
      System.out.println("The sum is "   sum   " and the average of your 5 numbers is "   sum / 5   ".");
}

uj5u.com熱心網友回復：

class fivePositiveNumbers{
    public static void main(String[] args){
        Scanner keyboard = new Scanner(System.in);
        int userNumber;
        int sum = 0;
        System.out.println("This program will give the sum and average of 5 positive integers,");

        int ctr = 0;

        for(;;){
            System.out.println("Enter number "   (ctr 1)   ": ");
            try{
                userNumber = keyboard.nextInt();
                if(userNumber <= 0){
                    throw new Exception("The integer must be positive.");
                }
                sum = sum   userNumber;

                ctr  ;
            } catch(InputMismatchException e){
                System.out.println("This data type is incorrect.");
                keyboard.nextLine();
            } catch(Exception e){
                System.out.println(e.getMessage());
                keyboard.nextLine();
            }

            if (ctr == 5) break;
        }

        System.out.println("The sum is "   sum   " and the average of your 5 numbers is "   sum / 5   ".");
    }
}

標籤：爪哇

上一篇：如何使用CSS翻轉svg影像

下一篇：androidx.preference.SwitchPreferenceCompat無法轉換為androidx.preference.PreferenceGroup