问在Java中无重复地向数组添加新元素

EN

import java.util.Scanner;

public class Control {

public void run() {


    while (true) {
        Menu menu = new Menu();
        menu.getMainMenu();

        try {
            Scanner scan = new Scanner(System.in);

            int selection = scan.nextInt();
            switch (selection) {
                case 1:
                    for (Student student : students) {
                        System.out.print(student.getName() + " ");
                    }
                    break;
                case 2:
                    for (Module module : modules) {
                        System.out.print(module.getName() + " ");
                    }
                    break;
                case 3:
                    ...
                case 4:
                    ...
                case 5:
                    // Print out students 
                    System.out.println("select a student: ");
                    for (int i = 0; i < students.length; i++) {
                        System.out.println(i + " " + students[i]);
                    }

                    selection = scan.nextInt();

                    ############################
                    Confusion here
                    ############################

                case 6:
                    System.out.println("Goodbye!");
                    System.exit(0);
                    break;
                default:
                    System.out.println("Invalid option selected. You must enter a number between 1 & 6!");
            } // end switch

        } catch (Exception e) {
            System.out.println("Invalid entry. You must enter a number between 1 & 6");
        }
    } // end while

}
}