How do I create a switch-statement in my main class that when that case is selected will run another main class in my program?

I have multiple classes such as customer, customers, employee, employees, product, products. The programs with 's' are main classes. I have one Main class, I want this to be the start point of the program. I'd like a switch-statement in it. I'd like to ask user for input 1-3 and then run that main class from their input. Such as if input is 1 it will run the customers main, etc. How do I do this?

import java.util.Scanner;

public class Main {

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

        //run customer add/edit/remove


        int choice = 0;
        while (true) {
            displayMenu();

            switch (choice) {
                case 1:
                    customers.main(null);


                    break;
                case 2:

                    cars.main(null);

                    break;
                case 3:
                    Staff.main(null);

                    break;
            }

        }

    }


    private static void displayMenu() {
        Scanner input;
        {
            input = new Scanner(System.in);
            {
                System.out.println("1. Customers");
                System.out.println("2. Cars");
                System.out.println("3. Staff");

                System.out.println("Which would you like to add/edit: ");
                String choice = input.nextLine();
            }
        }
    }
}


My other classes are fairly similar to this:
import java.util.Scanner;
import java.util.concurrent.CopyOnWriteArrayList;

//creates and array of the customers
public final class customers {
    public static void main(String[] args) throws InputValidationException {

        //add new customer
        CopyOnWriteArrayList<customer> customers = new CopyOnWriteArrayList<>();
        //List will fail in case of remove due to ConcurrentModificationException

        //loop getting input
        //input 'q' to quit

        Scanner input;
        {
            //scanner to get the input

            input = new Scanner(System.in);

            {
                while (true) {
                    //ask user for input and get input
                    System.out.println("Enter id (press 'q' to quit): ");
                    String temp = input.nextLine();
                    if (temp.equals("q")) break;

                    int id = Integer.parseInt(temp);

                    System.out.println("Enter first name:");
                    String firstName = input.nextLine();

                    System.out.println("Enter last name:");
                    String lastName = input.nextLine();



                    //add to array list
                    customers.add(new customer(id, firstName, lastName));


                }

            }
        }

        //Display All
        System.out.println("Current List: ");
        for (customer customer : customers) {
            System.out.println(customer.toString());
        }

        // search
        System.out.println("Enter name to search and display");
        String searchString = input.nextLine();
        for (customer customer : customers) {
            if (customer.search(searchString) != null) {
                System.out.println(customer.toString());
            }
        }


        //Remove
        System.out.println("Enter name to search & remove");
        searchString = input.nextLine();
        for (customer customer : customers) {
            if (customer.search(searchString) != null) {
                System.out.println(customer.toString() + " is removed from the List");
                customers.remove(customer);
            }
        }


    }
}

The customer class just contains variables, setters, getters and constructors

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        String input;
        do {
            input = displayMenu();
            switch (input) {
                case "1":
                    customers.main(args);
                    break;
                case "2":
                    cars.main(args);
                    break;
                case "3":
                    Staff.main(args);
                    break;
            }
        } while (!"exit".equals(input));
    }

    private static String displayMenu() {
        Scanner input = new Scanner(System.in);
        System.out.println("1. Customers");
        System.out.println("2. Cars");
        System.out.println("3. Staff");

        System.out.println("Which would you like to add/edit: ");
        return input.nextLine();
    }
}

class customers {
    public static void main(String[] args) {
        System.out.println("hello from 'customers'!");
    }
}

class cars {
    public static void main(String[] args) {
        System.out.println("hello from 'cars'");
    }
}

class Staff {
    public static void main(String[] args) {
        System.out.println("hello from 'Staff'");
    }
}