java - not able to use readFile() function

Question

I am trying to use readFile function from Container super class but I trigger FileNotFound exception under stack. What am I missing here?

public static final List<String> readFile(String fileName) throws FileNotFoundException, IOException {
        
        
        List<String> result = new ArrayList<>();

        try (Scanner s = new Scanner(new File(fileName))) {
            while (s.hasNextLine()) {
                result.add(s.nextLine());
                s.close();
            }
            return result;
           
        }

            }

public Stack(String fileName) throws FileNotFoundException, IOException {
        
        stack = new ArrayList<String>();
        String obj = (String) Stack.readFile(fileName).get(0);
        stack.add(obj);
                        
                    if(obj.startsWith("Stack"))
                            {
                        stack.add(obj.substring(4).strip());
                    }
                }
            
                

try to read file under Stack function by using readFile function.