java - 脚本正在移动过去的语句并出错

Question

我有一个脚本，应该是豪华邮轮旅行社的主菜单。主菜单显示一系列可供选择的选项，用户可以在它们之间进行选择。

        Luxury Ocean Cruise Outings
        System Menu

[1] Add Ship            [A] Print Ship Names
[2] Edit Ship           [B] Print Ship In Service List
[3] Add Cruise          [C] Print Ship Full List
[4] Edit Cruise         [D] Print Cruise List
[5] Add Passenger       [E] Print Cruise Details
[6] Edit Passenger      [F] Print Passenger List
[x] Exit System

Enter a menu selection:

同样，如果用户选择 1 或 3，则这些功能将启动。问题出在这两组方法上，一旦完成，程序就会从 addShip() 中中断；或 addCruise();它会出错，就好像代码试图自己做出选择而不是等待用户输入一样，它实际上就像返回到方法本身一样。

这是完成其中一个方法然后返回 main 后的结果。

    Luxury Ocean Cruise Outings
        System Menu

[1] Add Ship            [A] Print Ship Names
[2] Edit Ship           [B] Print Ship In Service List
[3] Add Cruise          [C] Print Ship Full List
[4] Edit Cruise         [D] Print Cruise List
[5] Add Passenger       [E] Print Cruise Details
[6] Edit Passenger      [F] Print Passenger List
[x] Exit System

Enter a menu selection: Exception in thread "main" 
Ship name: java.util.NoSuchElementException: No line found
    at java.base/java.util.Scanner.nextLine(Scanner.java:1651)
    at luxuryV2/luxuryV2.Driver.addShip(Driver.java:233)
    at luxuryV2/luxuryV2.Driver.mainMenu(Driver.java:46)
    at luxuryV2/luxuryV2.Driver.main(Driver.java:23)

这里用于调试的是 mainMenu();

    public static void mainMenu() {
        char choice = '0';
        Scanner scnr = new Scanner(System.in);
                displayMenu();
                try {
                    //scnr.next();
                    choice = scnr.next().charAt(0); // might throw an exception
                } catch (Exception e) {
                    // TODO: handle exception
                    System.out.println("\n\nException caught - " + e);
                }
                while (choice != 'x') {             
                    if (choice == 'x') {
                        break;
                    }
                    else if (choice == '1') {
                        addShip();
                        displayMenu();
                    }
                    else if (choice == '2') {
                        editShip();
                        displayMenu();
                    }   
                    else if (choice == '3') {
                        addCruise();
                        displayMenu();
                    }
                    else if (choice == '4') {
                        editCruise();
                        displayMenu();
                    }
                    else if (choice == '5') {
                        addPassenger();
                        displayMenu();
                    }
                    else if (choice == '6') {
                        editPassenger();
                        displayMenu();
                    }
                    else if (choice == 'A' || choice == 'a') {
                        printCruiseList("name");
                        displayMenu();
                    }
                    else if (choice == 'B'|| choice == 'b') {
                        printCruiseList("active");
                        displayMenu();
                    }
                    else if (choice == 'C' || choice == 'c') {
                        printCruiseList("full");
                        displayMenu();
                    }
                    else if (choice == 'D' || choice == 'd') {
                        printShipList("list");
                        displayMenu();
                    }
                    else if (choice == 'E' || choice == 'e') {
                        printShipList("details");
                        displayMenu();
                    }
                    else if (choice == 'F' || choice == 'f') {
                        printPassengerList();
                        displayMenu();
                    }
                    else {
                        System.out.println("\nSomething went wrong");
                        System.out.print("\nChoice: ");
                    }
                }
            //close scanner
            scnr.close();

这是 addShip() 的方法； (*注意，它与 addCruise(); 方法非常相似，为了便于阅读，我不会在此处包含它。)

    public static void addShip() {
        Scanner sc = new Scanner(System.in);
        //System.out.println("\naddShip method not complete.");
        // complete this method
        //shipName; roomBalcony; roomOceanView; roomSuite; roomInterior; inService;
        Ship vessel = new Ship();
        System.out.print("\nShip name: ");
        vessel.setShipName(sc.nextLine());
        //set ship space (Balcony)
        System.out.print("How many balcony rooms: ");
        vessel.setRoomBalcony(sc.nextInt());
        //set ship ocean view rooms (int)
        System.out.print("How many Ocean Veiw rooms: ");
        vessel.setRoomOceanView(sc.nextInt());
        //set suite rooms (int)
        System.out.print("How many Suit rooms: ");
        vessel.setRoomSuite(sc.nextInt());
        //set interior rooms
        System.out.print("How many interior rooms: ");
        vessel.setRoomInterior(sc.nextInt());
        //set active service
        System.out.print("Is the Ship in active service?\n"
                + "1. Yes"
                + "\n2. No"
                + "\nChoice: ");
        int choice;
        choice = sc.nextInt();
        if (choice == 1) {
            vessel.setInService(true);
        }
        else if (choice == 2) {
            vessel.setInService(false);
        }
        else {
            System.out.println("You entered an incorrect value, setting " + vessel.getShipName() + "to Inactive.");
            vessel.setInService(false);
        }
        //add vessel to list of ships
        shipList.add(vessel);
        //close scanner.
        //sc.next();
        sc.close();

    }

Answer 1

显然问题是关闭扫描仪对象本身，我不明白根本原因，但代码确实在扫描仪对象关闭后返回并尝试读取一行。但一旦我注释掉 close();在扫描仪对象上声明代码不再抛出异常。