异常在线程“主”java.util.NoSuchElementException无法找到我的情况的解决方案

Question

我已经看过每个人在哪里合理的解释，我怎样才能解决这个问题。有人可以看我的代码，并给我一些建议。

这里是我的代码：

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; 
    } 
} 

我得到的错误：在线程 “主要” java.util.NoSuchElementException

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

你的问题是在调用read.close()您的main方法。这不仅关闭了扫描仪，还关闭了System.in流。意思是说，无论何时您需要它（例如在您的printMenu方法中），它都不可用。

在你的情况下，close()调用是不必要的，你可以安全地删除它。