输入错误后，＃Java跳过了switch语句

Question

这是一个测试程序，供用户在员工和经理之间进行选择。如果用户选择员工，它将指导用户登录，经理也是如此。但是，当我错误地输入第一个选择时，当循环指示我输入另一个输入时，我正确输入输入，程序将跳过switch语句（它指示我登录）。为什么？

import java.util.*;

public class Main {

    public static void main(String args[]) {
        Scanner scan = new Scanner(System.in);
        int select = 0;

        ArrayList<Manager> manager = new ArrayList<Manager>();
        ArrayList<Staff> staff = new ArrayList<Staff>();
        staff.add(new Staff("LOL","LOL","Slol","asdasd"));
        manager.add(new Manager("Jason","Hew","Msdasd","asdasd"));

        do {
            try {
                select = Menu();

                switch(select) {
                    case 1:
                        SLogIN(staff);
                        break;
                    case 2:
                        MLogIN(manager);
                        break;
                    default:
                        select = Menu();
                }
            }catch (InputMismatchException e) {
               System.out.println("Invalid Selection.");
               System.out.println("Please choose only from the options above");
            }
        }while(select < 1 || select > 2);
    }

    public static int Menu() {
        Scanner scan = new Scanner(System.in);
        int input = 0;

        System.out.printf("Who are you? \n");
        System.out.printf("1. Staff\n");
        System.out.printf("2. Manager\n");
        System.out.printf("Your Answer : ");

        try{
            input = scan.nextInt();
        }catch (Exception e){
            System.out.println("Invalid Selection.");
            System.out.println("Please choose only from the options above.");
        }

        return input;
    }

    public static boolean MLogIN(ArrayList<Manager> a) {
        boolean valid = true;
        Scanner scan = new Scanner(System.in);

        System.out.print("Enter Manager ID :");
        String id = scan.next();
        System.out.print("Enter Password :");
        String pass = scan.next();

        if(id.startsWith("M")) {
            valid = true;
            for(int i = 0; i < a.size(); i++) {
                if(id.equals(a.get(i).getID())) {
                    valid = true;
                    if(pass.equals(a.get(i).getPass())) {
                        valid = true;
                    }
                    else {
                        valid = false;
                        System.out.println("Invalid Username or Password.");
                    }
                }
                else {
                    System.out.println("Invalid Username or Password.");
                    valid = false;
                }
            }
        }
        else {
            valid = false;
            System.out.println("Invalid Username or Password.");
        }

        return valid;
    }

    public static boolean SLogIN(ArrayList<Staff> a) {
        boolean valid = true;
        Scanner scan = new Scanner(System.in);

        System.out.print("Enter Staff ID :");
        String id = scan.next();
        System.out.print("Enter Password :");
        String pass = scan.next();

        if(id.startsWith("S")) {
            valid = true;

            for(int i = 0; i < a.size(); i++) {
                if(id.equals(a.get(i).getID())) {
                    valid = true;

                    if(pass.equals(a.get(i).getPass())) {
                        valid = true;
                    }
                    else {
                        valid = false;
                        System.out.println("Invalid Username of Password.");
                    }
                }
                else {
                    System.out.println("Invalid Username or Password.");
                    valid = false;
                }
            }
        }
        else {
            valid = false;
            System.out.println("Invalid Username or Password.");
        }

        return valid;
    }
}

Answer 1

删除default块。在select = Menu();之后，您已经在do-while循环的顶部放置了try。

do {
    try {
        select = Menu(); // <-- this is at the top.

        switch (select) {
        case 1:
            SLogIN(staff);
            break;
        case 2:
            MLogIN(manager);
            break;
        // default:
        // select = Menu();
        }
    } catch (InputMismatchException e) {
        System.out.println("Invalid Selection.");
        System.out.println("Please choose only from the options above");
    }
} while (select < 1 || select > 2);