error: non-static method gettaskdata() cannot be referenced from a static context

Question

trying to program a simple note taking app and I converted an array to an arraylist and took it out of being static and android studio is pointing out the error on "gettaskdata"

 taskData = (ArrayList)tData.gettaskdata();

    recView = (RecyclerView)findViewById(R.id.task_list);
    recView.setLayoutManager(layoutManager);
    btn1 = (Button)findViewById(R.id.btn1);

    adapter = new tAdapter(tData.gettaskdata(),this);

here is where "gettaskdata"originates

    private  String [] task0 = {"task 1", "task 2", "task 3"};
   private List<String> task1 = new ArrayList<String>(Arrays.asList(task0));
    private  final int [] icons = {R.drawable.ic_check_box_outline_blank_black_24dp,R.drawable.ic_check_box_black_24dp};
    public   List<tItem> gettaskdata(){
        List<tItem> t  =  new ArrayList<>();

        for (int x=0;x<task0.length;x++){
            tItem i = new tItem();
            i.setTasks(task1.get(x));
            i.getImageResId(icons[0]);
            t.add(i);
        }
        return t;
    }