java Try catch in switch语句退出选项

Question

我遇到的问题是，当我键入0作为菜单选项（即退出程序的选项）时，输出为：

无效选择，请输入菜单选项编号0-10

感谢您使用成绩册程序，祝您有愉快的一天

当它应该只显示感谢您使用程序消息而不是无效选择消息时

这是我的密码：

import java.io.IOException;
import java.util.Scanner;
import java.util.Arrays;
import java.util.InputMismatchException;

public class Tester
      {
       public static void main(String[] args) throws IOException
         { 

      Scanner kbReader = new Scanner (System.in);
      boolean loop = true;
      int choice = 0;
      Student array[] = null;
      System.out.printf("%50s", "Welcome to the Gradebook Program!");
      while(loop){
        do
         {
try
{
choice = Student.printMenu();

int numStudents;

switch(choice)
{       
  case 1:
    Gradebook.classInfo();
    numStudents = Gradebook.getNumStudents();
    array = Student.inputStudents(numStudents);
    Student.printGrades(array);
    break;

  case 2:
    array = Student.addStudent(array);
    Student.printGrades(array);
    break;

  case 3:
    int target = Student.getStudentToDelete(array);
    array = Student.deleteStudent(array, target);
    Student.printGrades(array);
    break;

  case 4:
    Student.editStudent(array);
    Student.printGrades(array);
    break;

  case 5:
    Student.printGrades(array);
    break;

  case 6:
    array = Student.inputGrades();
    break;

  case 7:
    Student.outputToFile(array);
    break;

  case 8:
    Student.search(array);
    break;

  case 9: 
    Student.studentHighest(array);
    break;

  case 10:
    Student.assignmentHighest(array);
    break;

  default:        
    System.out.println("\nInvalid choice, please enter a menu option number 0-10");
}

    }
catch(InputMismatchException e)
{
  System.out.println("Error: Invalid input, please enter a menu option number 0-10");11
}
   }
       while(choice != 0);
   loop = false;
    System.out.println("\nThank you for using the Gradebook Program, have a nice day.");
}
}
}

Answer 1

您需要向交换机添加case 0:选项：

switch(choice)
{   
    case 0: break;
    case 1: ...
        break;
    ...
}

添加case 0选项将阻止它进入开关中的默认情况。然后它将退出循环，显示“谢谢”消息，然后退出

Answer 2

switch语句没有case 0:。因此，它被引导到默认情况。之后的逻辑是确认0并退出循环

正如我打字时在评论中提到的