如何在switch语句中声明helper的方法

Question

在下面的代码中，如何将帮助程序的方法放入交换机中？

我尝试在声明帮助程序类之前将System.out.println语句放入开关中，但它不起作用。

在不必过多更改代码的情况下，启动帮助程序类的最简单方法是什么？

public static void Check(double result){

    Scanner keyboard = new Scanner(System.in);
    System.out.print("Enter the 13 digits of the ISBN, seperating each one with the enter key: ");
    String isbn = keyboard.next();
    result = 0;

    for(int x = 0; x < 14; x++) {
    if (x% 2 != 0) {
        double b = Character.getNumericValue(isbn.charAt(x));
        double mul = (b*3);
        result += mul; 
    }
}

public static double method(double[] args) {                                        
    Scanner keyboard = new Scanner(System.in);
    System.out.println("Please enter a number for X:");
    double x = keyboard.nextDouble();
    double result = 0;
    double number1 = 0;

    do {    
        number1 = (6 * (Math.pow(x,4)) - 13 * (Math.pow(x, 3)) - 18 * (Math.pow(x,2)) + 7 * x + 6) / (24 * (Math.pow(x, 3)) - 39 * (Math.pow(x, 2)) - 36 * x + 7);
        result = (x - number1);
        x = result;
        System.out.println(x);

    } while (Math.abs(number1) >= 0.001);
        System.out.println("the answer is:" + Math.round(result));

    return result;
}

public static boolean formula(String[] args) {
    Scanner keyboard = new Scanner(System.in);
    System.out.println("Please enter a,b and c with the enter key between");
    double a = keyboard.nextDouble();
    double b = keyboard.nextDouble();
    double c = keyboard.nextDouble();
    double discriminant = b * b - 4 * a * c;
    boolean good = false;
    good = (discriminant < 0);

    if (discriminant < 0) {
        System.out.println("No roots :(");
    } else if (discriminant == 0) {
        System.out.println("The single root is : " + ((-b + Math.sqrt(discriminant)) / (2 * a)));
    } else {
        System.out.println("The single root is : " + ((-b + Math.sqrt(discriminant)) / (2 * a)));
        System.out.println("The single root is : " + ((-b - Math.sqrt(discriminant)) / (2 * a)));
    }

    return good;
}

public static void main(String[] args) {
    Scanner keyboard = new Scanner(System.in); 
    System.out.println("hi! if you want to do a ISBNnumber checker type: 1. If you want newton's meathod type: 2. If you want to check quadractic formula type: 3.");
    int change = keyboard.nextInt();

    switch (change) {
        case 1: change = 1;

                break;
        case 2: change = 2;
                break;
        case 3: change = 3;
                break;
    }
}
}