private static void displayMenu(Set<Employee> employees) throws IOException {

        //Any initial number different from 1, 2, 3, 4 and 0
        int input = 6;

        while ( input != 0 ) {
            System.out.println("Enter 1 if you want to read data from the file.");
            System.out.println("Enter 2 if you want to write data to the file.");
            System.out.println("Enter 3 if you want to add data about new employee manually.");
            System.out.println("Enter 4 if you want to delete some employee.");
            System.out.println("Enter 5 if you have created employees list in order to perform б) и в) " +
                    "items of the task");
            System.out.println("And finally if you want to exit, please enter 0.");
            input = scanner.nextInt();
            switch (input) {
                case 1:
                    employees = readEmployees();
                    printEmployees(employees);
                    break;
                case 2:
                    writeEmployees(employees);
                    System.out.println("\nThe employees catalog was saved into the <Employees.out> file.\n");
                    break;
                case 3:
                    addEmployees(employees);
                    break;
                case 4:
                    System.out.println("\nEnter an employee last name that you want to remove:");
                    String lastName = scanner.next();
                    System.out.println("Enter an employee first name that you want to remove:");
                    String firstName = scanner.next();
                    System.out.println("Enter a salary of this person:");
                    Double salary = scanner.nextDouble();
                    System.out.println();
                    removeEmployee(employees, lastName, firstName, salary);
                    break;
                case 5:
                    someTasks(employees);
                    break;
                default:
            }
        }
    }