Firestore addSnapshotListener with list/array in Java

I am trying to use addSnapshotListener to listen to the changes of radiobutton in Firestore, which works with the string. I simply want to categorize better by grouping the response with a List. However, I found that there is not a method for snapshot.getList() and therefore I tried with

List<String> participate = snapshot.getList("Would you like to participate"); which doesn't work. I wonder how would I group my radiobutton response within a list to better organize the data in Firestore? Thank you in advance!

Below is the code I am working with for two radiobutton

Global:

String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
FirebaseFirestore db = FirebaseFirestore.getInstance();
DocumentReference uidRef = db.collection("users").document(uid);
RadioGroup radioGroup;
RadioButton yesButton;
RadioButton noButton;

For the OnCreate,

        yesButton = findViewById(R.id.a1);
        noButton = findViewById(R.id.a2);
        radioGroup = findViewById(R.id.radioGroup);
        String yes = yesButton.getText().toString();
        String no = yesButton.getText().toString();
 

addSnapshotListener to listen the changes

   uidRef.addSnapshotListener(new EventListener<DocumentSnapshot>() {
                        @Override
                        public void onEvent(@Nullable DocumentSnapshot snapshot, @Nullable FirebaseFirestoreException e) {
                            if (e != null) {
                                Log.w(TAG, "Listen failed.", e);
                                return;
                            }
    
                        if (snapshot != null && snapshot.exists()) {
                            String participate = snapshot.getString("Would you like to participate");
                            if (participate != null) {
                                    yesButton.setChecked(true);
                                } else {
                                    noButton.setChecked(true);
                                }
                            }
                        }
        });

The two radio buttons:

 yesButton.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        if (yesButton.isChecked()) {
                            Map<String, Object> update = new HashMap<>();
                            update.put("Would you like to participate", yes);
                            uidRef.update(update).addOnCompleteListener(new OnCompleteListener<Void>() {
                                @Override
                                public void onComplete(@NonNull Task<Void> task) {
                                    Toast.makeText(getApplicationContext(), "Response updated ", Toast.LENGTH_SHORT).show();
                                }
                            });
                        }
                    }
                });

        noButton.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        if (noButton.isChecked()) {
                            Map<String, Object> update = new HashMap<>();
                            update.put("Would you like to participate", no);
                            uidRef.update(update).addOnCompleteListener(new OnCompleteListener<Void>() {
                                @Override
                                public void onComplete(@NonNull Task<Void> task) {
                                    Toast.makeText(getApplicationContext(), "Response updated ", Toast.LENGTH_SHORT).show();
                                }
                            });
                        }
                    }
                });
        

Expected Firestore result: