为什么我会收到 NoSuchElementException？

Question

Here is my code:

while (menuExit == true) {
        System.out.println (SEPARATE_LINE);
        System.out.println ("Which do you want to do ? ");
        System.out.println (SEPARATE_LINE);
        System.out.println ("1.Register");
        System.out.println ("2.Sign in");
        System.out.println ("3.Check shop status");
        System.out.println ("0.Exit");
        System.out.println (SEPARATE_LINE);
        System.out.print("Please enter your choice as number:");
        do{
        try{
        int selectMain = input.nextInt();
        if(selectMain == 1){
            register(currentNum , customers);
            customers.clear();
            customers = ReadData.readCustomerData();
         }else if(selectMain == 2){
            signIn(customers,historys,cusData,hisData);
        }else if(selectMain == 3){
            CheckData.checkShopStatus(shops,shopData);
            
        }else if(selectMain == 0){
            System.out.println ("Thank you");
            menuExit = false;
        }else {
            System.out.println ("Your input are wrong , Please enter again.");
        }
        continueInput = false;
        }catch(InputMismatchException ex){
            System.out.println("Please enter again.");
            input.nextLine();
        }
        
    }while (continueInput);
    input.close();

This is the menu of my program, when I enter into one of these selection and come back to the menu, I got NoSuchElementException, the error point to the line int selectMain = input.nextInt();. Please someone help me, thank you for your attention.

Answer 1

You have continueInput = false in the try block in such a way that it means that it will run regardless of the user input. This means the dowhile loop exits on the next try, and the input is closed. however, because this is in another while loop, it tries to get another input, even though the input scanner is closed. This gets you the NoSuchElementException.