Sum in Firebase Real-time database children - Android Sudio

 

private void countAndSum() {
    FirebaseDatabase.getInstance().getReference().child("Hospital").child("Users").child(uid).child("Cart")
            .addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot snapshot) {

                    int sum = 0;

                    if(snapshot.exists()){
                        for(DataSnapshot ds : snapshot.getChildren()){
                            Map<String, Object> map = (Map<String, Object>) ds.getValue();
                            Object amount = map.get("Amount");
                            int pValue = Integer.parseInt(String.valueOf(amount));
                            sum += pValue;

                            tTotalItemsCost.setText("Rs." + String.valueOf(sum));
                        }
                    }
                }

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

                }
            });
}