线程“main”中的异常 java.util.NoSuchElementException 找不到我的案例的解决方案

Question

我已经向每个人寻找了关于如何解决问题的合理解释。有人可以看看我的代码并给我一些建议。

这是我的代码：

import java.util.Scanner;

public class ShoppingCartManager {

    public static void printMenu(ShoppingCart cart){
        Scanner read = new Scanner(System.in);
        String input = " ";

      /*  String itemName = "none";
        String itemDescription = "none";
        int itemPrice = 0;
        int itemQuantity = 0;*/

        System.out.println("MENU");
        System.out.println("a - Add item to cart");
        System.out.println("d - Remove item from cart");
        System.out.println("c - Change item quantity");
        System.out.println("i - Output items' descriptions");
        System.out.println("o - Output shopping cart");
        System.out.println("q - Quit");

        //ItemToPurchase shopCart = new ItemToPurchase();

        input = read.next();
        read.close();



        switch (input){

            case "q" : System.out.println("Quit");
            break;
        }

    }

    public static void main(String[] args){
        Scanner read = new Scanner(System.in);
        String customerName = "none";
        String todaysDate = "none";

        System.out.println("Enter the Customer's name: ");
        customerName = read.nextLine();
        System.out.println("Enter Today's Date: ");
        todaysDate = read.nextLine();
        ShoppingCart cart = new ShoppingCart(customerName, todaysDate);


        System.out.println("Customer Name: " + cart.getCustomerName());
        System.out.println("Today's Date: " + cart.getDate());

        read.close();

        printMenu(cart);



        return;
    }
}

我得到错误：

线程“主”java.util.NoSuchElementException 中的异常

at java.util.Scanner.throwFor(Scanner.java:862)
at java.util.Scanner.next(Scanner.java:1371)
at ShoppingCartManager.printMenu(ShoppingCartManager.java:24)
at ShoppingCartManager.main(ShoppingCartManager.java:54)

Answer 1

您的问题是在您的 main 方法中调用 read.close()。这不仅会关闭 Scanner，还会关闭 System.in 流。这意味着任何时候您需要它（例如在您的 printMenu 方法中），它都不可用。

在您的情况下，close() 调用根本是不必要的，您可以安全地删除它。