在用户键入从Java中的另一个方法返回到主菜单的选项后，是否有一种方法来显示main方法？

Question

我正在做一个Java项目，但我有点卡住了，主要方法是要求用户从菜单中输入一个数字来显示它，按下10它将用户带到分级子菜单方法，在那里用户可以选择从菜单中键入一个数字1-4来显示它，因为他们也可以键入0来退出，我的想法是如果键入0,它会返回到显示主要方法，有没有办法做到这一点？以下是我到目前为止的代码：

import java.util.Scanner;
public class MidTermProject {

    public static void main(String[] args) {
        
        Scanner keyboard = new Scanner(System.in);
        
        System.out.println("Here is the sample of menu choices for Main Menu.");
        
        System.out.println("\nWelcome to University Enrollment" + "\n1. Create Student" +
                            "\n2. Create Course" + "\n3. Create Enrollment" + "\n4. Edit Student"
                            + "\n6. Edit Enrollment" + "\n8. Display Course" + "\n9. Display Enrollment"
                            + "\n10. Grades Sub Menu" + "\n0. --- Quit ---");
        
        System.out.println("Please enter a valid choice(1-10, 0 to Quit) :");
        int userInput = keyboard.nextInt();
        
        if(userInput == 1) {
            CreateStudent();
        } else if(userInput == 10) {
            GradesSubMenu();
        }

    }
    
    public static void CreateStudent() {
        String FullName;
        String address;
        String city;
        String state;
        int zipcode;
        String phone;
        String email;
        
        Scanner keyboard = new Scanner(System.in);
        
        System.out.print("\nPlease enter your information bellow.\n" + "\nFull Name: ");
        FullName = keyboard.next();
        
        System.out.print("Address: ");
        address = keyboard.next();
        address = keyboard.next();
        
        System.out.print("City: ");
        city = keyboard.next();
        
        System.out.print("State: ");
        state = keyboard.next();
        state = keyboard.next();
        
        System.out.print("Zip Code: ");
        zipcode = keyboard.nextInt();
        
        System.out.print("Phone Number(format xxx-xxx-xxxx): ");
        phone = keyboard.next();
        
        System.out.print("Email Address: ");
        email = keyboard.next();
        
    }
    
    public static void GradesSubMenu() {
        int userInput;
        
        Scanner keyboard = new Scanner(System.in);
        
        System.out.println("\nGrades Sub Menu:\n" + "\nGrades Menu" + "\n1. View Grades By Student"
                            + "\n2. View Grades by Course" + "\n3. Edit Grades by Student" + 
                            "\n4. Edit Grades by Course" + "\n0. -- Exit to Menu --");
        
        System.out.print("Please enter a valid choice(1-4, 0 to Exit):");
        userInput = keyboard.nextInt();
        
        *if(userInput == 0) {
            main(String[] args);//how to reference to display back the main method
        }*
    }

}

Answer 1

如果确实需要，可以使用main(null)；代替main(string[]args)；

我对你的类做了一些修改...我建议你不要只使用静态方法。

import java.util.Scanner;

    public class MidTermProject {

    private Scanner scanner;

    public MidTermProject(Scanner scanner) {
        super();
        this.scanner = scanner;
    }

    public static void main(String[] args) {
        Scanner keyboardInputScanner = new Scanner(System.in);

        MidTermProject midTermProject = new MidTermProject(keyboardInputScanner);
        midTermProject.showMainMenu();
    }

    private void showMainMenu() {
        System.out.println("Here is the sample of menu choices for Main Menu.");

        System.out.println("\nWelcome to University Enrollment" + "\n1. Create Student" + "\n2. Create Course"
                + "\n3. Create Enrollment" + "\n4. Edit Student" + "\n6. Edit Enrollment" + "\n8. Display Course"
                + "\n9. Display Enrollment" + "\n10. Grades Sub Menu" + "\n0. --- Quit ---");

        System.out.println("Please enter a valid choice(1-10, 0 to Quit) :");
        int userInput = scanner.nextInt();

        if (userInput == 1) {
            createStudent();
        } else if (userInput == 10) {
            gradesSubMenu();
        }
    }

    public void createStudent() {
        String fullName;
        String address;
        String city;
        String state;
        int zipcode;
        String phone;
        String email;

        System.out.print("\nPlease enter your information bellow.\n" + "\nFull Name: ");
        fullName = scanner.next();

        System.out.print("Address: ");
        address = scanner.next();
        address = scanner.next();

        System.out.print("City: ");
        city = scanner.next();

        System.out.print("State: ");
        state = scanner.next();
        state = scanner.next();

        System.out.print("Zip Code: ");
        while (!scanner.hasNextInt()) { // make sure that the user gets an error if he enters a text, this could work
            scanner.next();
            System.out.println("Plase enter only numbers");
        }
        zipcode = scanner.nextInt();

        System.out.print("Phone Number(format xxx-xxx-xxxx): ");
        phone = scanner.next();

        System.out.print("Email Address: ");
        email = scanner.next();

        System.out.println(fullName);

    }

    public void gradesSubMenu() {
        System.out.println(
                "\nGrades Sub Menu:\n" + "\nGrades Menu" + "\n1. View Grades By Student" + "\n2. View Grades by Course"
                        + "\n3. Edit Grades by Student" + "\n4. Edit Grades by Course" + "\n0. -- Exit to Menu --");

        System.out.print("Please enter a valid choice(1-4, 0 to Exit):");
        int userInput = scanner.nextInt();

        if (userInput == 0) {
            System.out.println("0");
            this.showMainMenu();
        }
    }

    }