从另一个类调用方法以在 switch 语句中使用

Question

I'm trying to call a method from my UserController class to my MainController . However i can't seem to instantiate my method and therefore calling it has proved quite difficult.

Also the method I'm calling is to be used in a switch statement. Does this affect how i should go about it at all?

The createUser method. The method works code wise (tried having it in MainController ) i just don't know how to instantiate it without doing it through a switch statement.

  public static void createUser(){


   String username, password, repeatPassword, height, weight, address, email;

               int age, choice;
               double fitnessIndex; 

               String [] rank = {"Guld", "Platinum", "Diamond"};
               String [] sex = {"Mand","Kvinde"};

                System.out.println("Udfyld følgende for at blive oprettet som bruger: \n ");

                System.out.print("Navn:\n");
                username = input.nextLine();

                System.out.println("E-mail:  ");
                email = input.next();


                // Regular expression som presierer hva emailen skal inneholde for å være valid

                while (!email.matches("([a-zA-Z0-9_\\-\\.]+)@([a-zA-Z0-9_\\.\\.]+)\\.([a-zA-Z]{2,5})")) {
                    System.out.print("Ugyldig Email, prøv igjen\n");
                    email = input.next(); }


                System.out.println("Alder:  ");
                age = input.nextInt();



                // Brugeren velger mellom 2 predefinerte koen
                do {
                    System.out.println("Vælg dit koen: ");
                    data.printArray1(sex);
                    choice = input.nextInt();
                } while (choice < 1 || choice > sex.length);



                System.out.println("Hoejde:   ");
                height = input.next();

                System.out.println("Vaegt:  ");
                weight = input.next();

                System.out.println("Adresse:   ");
                address = input.next();

                System.out.println("Kondital:  ");
                fitnessIndex = input.nextDouble();



                // Brugeren velger mellom 3 predefinerte muligheter for medlemsskab

                do {
                    System.out.println("Vælg ranken som passer deg bæst: ");
                    data.printArray(rank);
                    choice = input.nextInt();
                } while (choice < 1 || choice > rank.length);


                //beder brugeren om at vælge og gentage sitt kodeord


                do {
                    System.out.println("Kodeord:  ");
                    password = input.next();

                    System.out.println("Gentag kodeord  ");
                    repeatPassword = input.next();

                    if (!password.equals(repeatPassword)) {
                        System.out.println("Kodeordet er forkert, prøv igen!");
                    }
                } while (!password.equals(repeatPassword));

                User Unapproved = new User(username, password, 1, age, sex[choice-1], height, weight, fitnessIndex, address, email, rank[choice-1]);
                data.getUnapproveds().add(Unapproved);

                System.out.println("\nDu er nu blivet oprettet som medlem og venter på godkenning ");
                System.out.println("Så snart du er godkent vil du kunne logge inn, Velkommen til Motion CBS!🏋️\n");

        } 

Switch statement and me trying to call the method in MainController

            do try {
            choice = input.nextInt();
            input.nextLine();
            switch(choice) {
                case 1:
                    login();
                    break;

                case 2:
                    createUser(); // opret medlemskab
                    break;

                case 3:
                    login();
                    break;

                case 4:
                    onExit();
                    break;

                default:
                    System.out.println("Ugyldigt valg! Prøv igen");
                    break;
            }
        } catch (InputMismatchException eObject) {
            System.out.println("\n Du har indtastet en forkert variabel og bliver nu returnert til stratsiden");
            input.nextLine();
        printStartMenu();
    }

    while (currentUser != null);
}

{
   UserController userController = new UserController();
   userController.createUser();  }

So to clarify once again. The method won't be called, since i don't know how to instantiate the method in UserController first. So the CreateUser at the very bottom is RED (not working)

Therefore point 2 in the switch statement doesn't work. Any help and tips are appreciated as i want to understand what i'm missing and why

EDIT I understand now that i haven't provided nearly enough information so i'll supplement under here

UserController extends MainController

 public class UserController extends MainController {

/**
 * The class constructor. Initializes the class and
 * its super class with instanses of the {@link MainController#data}
 * and {@link MainController#currentUser} objects.
 *
 * @param data        The instantiated data object.
 * @param currentUser The instantiated currentUser object.
 */
public UserController(Data data, User currentUser) {
    super(data, currentUser);
}

Maincontroller

protected Scanner input = new Scanner(System.in);

/** An instance of the Data class that holds all of the program data */
protected Data data;

/**
 *  The user currently logged in to the program.
 *  Defaults to null if no user is logged in.
 */
protected User currentUser;

/**
 * Default constructor for the Main Controller.<br>
 * Should <b>ONLY</b> be called from the Main Class, and only once.
 */

public MainController() {
    this.data = new Data();
}

/**
 * Constructor for instantiating when the Main Controller,
 * is the parent of a child controller.
 *
 * @param data          A reference to the instantiated Data object.
 * @param currentUser   A reference to the instantiated User object.
 */
public MainController(Data data, User currentUser) {
    this.data = data;
    this.currentUser = currentUser;
}

Answer 1

Since the createUser method is static, you can call it inside the Main controller using the Class in which the method resides, which in this case is UserController .

case 2:
       UserController.createUser(); 
       break;

Edit : The newly added code looks okay. Since I do not have the Data and User classes, I am assuming that there is anything wrong but at the same time I can give some points regarding the aspect of the code to clear any problems that you might be facing like with this one. You must be knowing most of the things, But just in case to clear any confusion you're facing:

I have absolutely no idea how to work around override and extends

extends is a keyword used to inherit a class. In the current context UserController is a sub-class/child-class and the MainController is the super-class/parent-class. Inheritance is forming of a relation between class. You can use it to inherit the code that was already written in a class(MainController) and so you don't need to type the same thing inside the newly created class(UserController) which need the same properties.

Eg : My parent is a human being. I(child) am a human being. I inherited the qualities of a human being from my parent(and my parent inherited their qualities from their parents and so on).

It is important to note that constructors cannot be inherited, which is why in your code inside the UserController constructor you are using super keyword to invoke the MainController constructor and pass the values to it. Fields(except private fields) and methods(Except constructor) can be inherited.

I have absolutely no idea how to work around override and extends

Overriding means that you are inheriting something from your parent, but you do not want it as it is and what to modify the implementation.

Eg : Suppose, you are inheriting a Jewellery shop from your parent. But you do not like it and so you chose to modify it in to a tea shop.

A small program would explain it better :

Parent class

public class parent {

public void wakeUp()
{
    System.out.println("I will wake up at 6am");
}

}

This is our parent class and it contains a method named wakeUp. Parent will wake up at 6am and so if this parent have a child then by default the parent will make the child also wake up at the same time(6am). In other words the child will inherit the qualities of the parent by default. You do not need to write any code inside the child class to get this quality(you just need to inherit the parent). It is like saying this is my parent and so I will get all the properties from my parent by default and here goes the code for that :

public class Child extends parent{


}

As we can see that we havent written anything inside the child class. But we have used the extends keyword which is declaring that the class named Child is the child of the class named Parent .

Now, overriding is when the child wants a different implementation. It is like saying I have different in views as compared to my parents when it comes to certain things.

Eg :

public class Child extends parent{

@Override
public void wakeUp()
{
    System.out.println("I will wake up at 10am");
}

}

Here, we are definiing the same method inside the child class. Wake up is the quality and this child doesn't like to wake up at 6am and so the child had overridden the quality(method) called wakeUp() and provided it's own implementation inside the body of the method. The child modified/overridden the quality that it got from the parent. But the parent's quality haven't changed. The parent will wake up at 6am and the child will wake up at 10am. I hope this helps you.

From this it is clear for us that we don't need to override a method if we want the same implementation/quality. So whatever is written inside the MainController is inherited by the UserController(with a few exception we have said earlier).

Answer 2

Since you seems to be struggling with inheritance and what you can and can't do from a superclass I would suggest that the best solution for now is to move the method createUser from UserController to MainController and removing static from the declaration and then simply delete the UserController class (of course move any other methods as well).

This will leave you with only one class and you can focus on getting your application to behave as you want. Introducing inheritance just for the sake of it is pointless and over engineering, once you have a running bug free version of your application then you could start considering re-factoring your code.