Variable 'singleChoiceAdapter' is accessed from within inner class, needs to be final or effectively final

Question

I created a function with name setRecyclerViewSingleItems so that i can restrict the user to select only one option from the given options ( those options are stored in arrrayList ). I want to create this function such that i can do this multiple times but without creating the function multiple times.

When i do that for a single type of list by defining their variables inside the function it works but not for every list.

So could anyone please explain me how can I solve this issue.

I tried what the IDE suggesting me by making a another final variable but after that app crashes with null pointer exception.

public class employer_after_login_form extends AppCompatActivity{
    RecyclerView typeOfOrgRV, typeOfSectorRV;
    ArrayList<String> typeOfOrgArrList, typeOfSectorArrList;
    Multiple_Choice_Adapter typeOfOrgAdapter;
    Multiple_Choice_Listener typeOfOrgListener;
    Single_Choice_Adapter typeOfSectorAdapter;
    Single_Choice_Listener typeOfSectorListener;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_employer_after_login_form);

        //[START : type of organization code here]
        typeOfOrgRV = findViewById(R.id.typeOfOrgRV);
        String[] typeOfOrgStr = getResources().getStringArray(R.array.typeOfOrganisation);
        typeOfOrgArrList = setArrayList(typeOfOrgStr);
        setRecyclerViewMultipleItems(typeOfOrgRV, typeOfOrgArrList, typeOfOrgAdapter, typeOfOrgListener);
        //[END]


        //[START : industry OR sector choice]
        typeOfSectorRV = findViewById(R.id.typeOfSectorRV);
        String[] typeOfSectorStr = getResources().getStringArray(R.array.typeOfOrganisation);
        typeOfSectorArrList = setArrayList(typeOfSectorStr);
        setRecyclerViewSingleItems(typeOfSectorRV, typeOfSectorArrList, typeOfSectorAdapter, typeOfSectorListener);
        //[END]
    }

    private void setRecyclerViewSingleItems(RecyclerView recyclerView, ArrayList<String> arrayList, Single_Choice_Adapter singleChoiceAdapter, Single_Choice_Listener singleChoiceListener) {
        singleChoiceListener = new Single_Choice_Listener() {
            @Override
            public void onSingleItemSelected(String s) {
                recyclerView.post(new Runnable() {
                    @Override
                    public void run() {
                        singleChoiceAdapter.notifyDataSetChanged();
                    }
                });
                Toast.makeText(employer_after_login_form.this, s, Toast.LENGTH_SHORT).show();
            }
        };
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        singleChoiceAdapter = new Single_Choice_Adapter(this, arrayList, singleChoiceListener);
        recyclerView.setAdapter(singleChoiceAdapter);
    }

    private void setRecyclerViewMultipleItems(RecyclerView recyclerView, ArrayList<String> arrayList, Multiple_Choice_Adapter multipleChoiceAdapter, Multiple_Choice_Listener multipleChoiceListener) {
        typeOfOrgRV.setHasFixedSize(true);
        typeOfOrgListener = new Multiple_Choice_Listener() {
            @Override
            public void onMultipleItemSelected(ArrayList<String> arrayList) {
                typeOfOrgRV.post(new Runnable() {
                    @Override
                    public void run() {
                        typeOfOrgAdapter.notifyDataSetChanged();
                    }
                });
                Toast.makeText(employer_after_login_form.this, arrayList.toString(), Toast.LENGTH_SHORT).show();
            }
        };
        typeOfOrgRV.setLayoutManager(new LinearLayoutManager(this));
        typeOfOrgAdapter = new Multiple_Choice_Adapter(this, typeOfOrgArrList, typeOfOrgListener);
        typeOfOrgRV.setAdapter(typeOfOrgAdapter);
    }

    private ArrayList<String> setArrayList(String[] stringArray) {
        ArrayList<String> arrayList = new ArrayList<>(Arrays.asList(stringArray));
        return arrayList;
    }

    /*@Override
    public void onMultipleItemSelected(ArrayList<String> arrayList) {
        Toast.makeText(this, arrayList.toString(), Toast.LENGTH_SHORT).show();
    }*/
}