数组我的循环中有一个错误。线程“main”java中出现异常。util。非接触性异常。错误是我的扫描仪？

Question

好的，看来我的主课遇到了一些问题。它在第二次运行时中断我的循环，并显示和错误。它说我的扫描仪从菜单中读取用户选择是创建错误？这是怎么回事，它在第一个循环中工作，但由于某种原因，它无法再次运行

"action = new Scanner(System.in).nextInt();" 

正在生成错误。有人知道为什么会发生这种情况吗？因为在用户选择菜单选项时，读取用户输入的整数非常重要

import java.util.Scanner; 
import java.io.FileWriter; 
import java.io.IOException;
import java.io.PrintWriter;
import java.lang.String; 
import java.lang.System;  

public class MainActions {

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

        int action = 0;

        while (action != 6) {

            Contact.menu();

            new Scanner(System.in);

            action = new Scanner(System.in).nextInt();

            if (action <= 0 || action > 6) {
                System.out.println("Invalid selection. ");
            }

            switch (action) {
            case 1:
                MainActions.addContactInfo();
                break;

            case 2:
                break;

            case 3:
                break;

            case 4:
                break;

            case 5:
                break;
            }
        }
    }

    public static void addContactInfo() {

        Contact contact;
        contact = new Contact();

        Scanner reader = new Scanner(System.in);
        System.out.println("Enter Contact Last Name:");
        String lastname = reader.nextLine();
        contact.setLastName(lastname);
        System.out.println("Enter Contact First Name: ");
        contact.setFirstName(reader.nextLine());
        System.out.println("Enter Contact Street Address: ");
        contact.setHouseAddress(reader.nextLine());
        System.out.println("Enter Contact City: ");
        contact.setCity(reader.nextLine());
        System.out.println("Enter Contact Zip Code: ");
        contact.setZip(reader.nextLine());
        System.out.println("Enter Contact Email: ");
        contact.setEmail(reader.nextLine());
        System.out.println("Enter Contact Phone Number: ");
        contact.setPhone(reader.nextLine());
        System.out.println("Enter Contact Notes: ");
        contact.setNotes(reader.nextLine());

        if (lastname.trim().equals("")) {
            System.out.println("\nLast name was blank, contact not saved.");
            System.exit(0);
        } else {
            ContactList list;
            list = new ContactList();
            list.add(contact);
            list.save();
            Contact c = contact;
            try (PrintWriter output = new PrintWriter(new FileWriter("contactlist.csv", true))) {
                output.printf("%s\r\n", c);
            } catch (Exception e) {}
        }
        reader.close();
    }
}

控制台：

1. Enter a new person
2. Print the contact list
3. Retrieve a person's information by last name
4. Retrieve a person's information by email address
5. Retrieve all people who live in a given zip code
6. Exit
1
Enter Contact Last Name:
asdf
Enter Contact First Name: 
asdf
Enter Contact Street Address: 
asdf
Enter Contact City: 
asdf
Enter Contact Zip Code: 
asdf
Enter Contact Email: 
asdf
Enter Contact Phone Number: 
asdf
Enter Contact Notes: 
asdf

Contact information has been saved.

Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at MainActions.main(MainActions.java:33)
1. Enter a new person
2. Print the contact list
3. Retrieve a person's information by last name
4. Retrieve a person's information by email address
5. Retrieve all people who live in a given zip code
6. Exit

Answer 1

new Scanner(System.in); // Remove this. Not needed.
action = new Scanner(System.in).nextInt();

等等，这不是问题所在。这是实际问题

reader.close();

你的addContactInfo()中的这一行是罪魁祸首。删除此项，您的代码将正常工作

此reader.close()关闭方法中的Scanner（扫描System.in），因为两者都在扫描System.in

希望这能解决你的问题。我只是碰巧找到了this question on SO。更多详细的解释，请查看这个

医生说：

公共作废关闭（）引发IOException

Closes this input stream and releases any system resources associated with this stream. The general contract of close is that it closes the input stream. A closed stream cannot perform input operations and cannot be reopened.

Answer 2

替换

new Scanner(System.in);

action = new Scanner(System.in).nextInt();

与

Scanner scan = new Scanner(System.in);

action = scan.nextInt();