How to use an arrayList and array in a method

Hi, i am currently doing my university work but i am stuck on one thing. I have made an array to hold car sales for 9 years according to the registration plate and an array list to hold the registration and information of each car.

I have made a method to add a cars details into the array list, but i also need to add the registration into the array of the car sales. I know how to put an arrayList into a method, but im not sure on how to put the array into the method aswell. Any help would be much appreciated.

Code:

public static void main (String[] args)
        {
            ArrayList<String> forSaleData = new ArrayList<String>();
     
            final int CAR_SALES = 9;
            int[] sales = new int[CAR_SALES];
            final int TOTAL_SALES = 200;
            int[] totalSalesValue = new int [TOTAL_SALES];
            double totalSales = 0;


public static void addCar(ArrayList<String> forSaleData)
          
       
           {
              Scanner in = new Scanner (System.in); 
              System.out.print("Enter Car registration: ");
              String reg = in.nextLine();
              char c = reg.charAt(3);
              if (Character.isDigit(c)){
               System.out.print("enter other info");
               String info = in.nextLine();
               String carInfo = reg + info;
               forSaleData.add(carInfo);
           }
            else {
                System.out.println("Registration is not valid");
           }