Firebase Realtime Database Update Data - Android Java

public void deleteTask(View view) {

    int index=listView.getPositionForView(view);
    String str= (String) arrayAdapter.getItem(index++);

    DatabaseReference ref = FirebaseDatabase.getInstance().getReference();
    Query taskQuery = ref.child("Todo").orderByChild("Task").equalTo(str);
    taskQuery.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot appleSnapshot: dataSnapshot.getChildren()) {
                appleSnapshot.getRef().removeValue();
            }
            arrayList.remove(listView.getPositionForView(view)); // remove the item from list
            arrayAdapter.notifyDataSetChanged();// notify the changed
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            Log.e("TAG", "onCancelled", databaseError.toException());
        }
    });

}

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference usersRef = rootRef.child("Users");
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        List<String> list = new ArrayList<>();
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            String uid = ds.getKey();
            list.add(uid);
        }

        //Do what you need to do with your list
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
    }
};
usersRef.addListenerForSingleValueEvent(valueEventListener);

FirebaseDatabase db = FirebaseDatabase.getInstance();

DatabaseReference userProfileRef = db.getReference("users").child(userId);

map.add("email",email)
map.add("name",name);
userProfileRef.update(map);

FirebaseDB.batch.child(batch).addValueValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            //Update recyclerview here
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {

        }
    });