error when add element at specified index in ArrayList [Java]

I have an error when adding an element at the specified index in ArrayList I'm using loop and variable it's increasing every time when looping

1. I tried to use a command arrayListName.add(index,thing) but this give me an error when assign second time problem ==> https://ibb.co/ZSQvywY .
2. I tried to loop without index but this all the time assign in index [0]

public class CollegeSystem {

    public static void printOptions() {
        System.out.println("Welcome to our university!");
        System.out.println("Operations:");
        System.out.println("1- College");System.out.println("a) Number of Departments");System.out.println("b) Number of Courses");System.out.println("c) Number of Professors");System.out.println("d) Number of Students");System.out.println("e) Report");
        System.out.println("2- Department");System.out.println("a) New");System.out.println("b) Number of Courses");System.out.println("c) Number of Students");System.out.println("d) Is Full");System.out.println("e) Enroll");System.out.println("f) Report");
        System.out.println("3- Course");System.out.println("a) New");System.out.println("b) Number of Students");System.out.println("c) Assign");System.out.println("d) Is assigned");System.out.println("e) Professor Name");System.out.println("f) Is Full");System.out.println("g) Enroll");System.out.println("h) Report");
        System.out.println("4- Professor");System.out.println("a) New");System.out.println("b) Display Salary");System.out.println("c) Get Raise");System.out.println("d) Report");
        System.out.println("5- Student");System.out.println("a) New");System.out.println("b) Report");
        System.out.println("6- Quit");
    }

    public static void main(String[] args) {
        // TODO code application logic here

        printOptions() ;
        Scanner in = new Scanner(System.in) ; 
        int d = 0 , c = 0  , p = 0 , s=0 ; 
        College AinShams = new College() ; 
        while (true){
            String option = in.nextLine() ; 
            if(!"6".equals(option)) {
                if ("2a".equals(option)) { // Define new department
                    System.out.println("Department Name:");
                    String depName = in.nextLine() ; 
                    System.out.println("Department Description:");
                    String depDescripe = in.nextLine() ;
                    System.out.println("Department Max Students:");
                    int max_num = in.nextInt() ;
                    in.nextLine() ; 
                    Department Department_Name = 
                    new Department(depName,   depDescripe, max_num); 
                    List<Department> departmentList;
                   //here create a new arrayList
                   departmentList = new ArrayList<>();
                 //try to add element without index
                   //  departmentList.add(Department_Name);
                 //try to add element with index
                   departmentList.add(d, Department_Name);
                    d++ ;
                    AinShams.setDepart(departmentList);      
                }
            }   
        }   
    } 
 }

I need to add an element in every time I loop without remove old data.