before update
I want update the value of Plavix 75mg:”50″. When user give a new value my code add a new value with a new ID instead of modifying the previous one. Here is the result.
after update
Please help me to fix this.
Here is my code.

    private void updatePharmaceutical(String documentId, String newDose, String newQuantity) {
        if (storeName != null) {
            CollectionReference storeCollection = db.collection(storeName);
            Map<String, Object> updates = new HashMap<>();
            updates.put("dose", newDose);
            updates.put("quantity", newQuantity);
            storeCollection.document(documentId).update(updates)
                    .addOnSuccessListener(aVoid -> {
                        Toast.makeText(this, "Successfully updated.", Toast.LENGTH_SHORT).show();
                        updateRealtimeDatabase(documentId, newQuantity); // Update Realtime Database with new quantity
                    })
                    .addOnFailureListener(e -> Toast.makeText(this, "Error caught while updating document", Toast.LENGTH_SHORT).show());
        }
    }

    private void updateRealtimeDatabase(String drugName, String newQuantity) {
        FirebaseUser currentUser = FirebaseAuth.getInstance().getCurrentUser();
        if (currentUser != null) {
            String userId = currentUser.getUid();
            DatabaseReference userRef = FirebaseDatabase.getInstance().getReference("Pharmacists").child(userId).child("drugData");

            // Update Realtime Database with new quantity for the corresponding drug
            userRef.child(drugName).setValue(newQuantity)
                    .addOnSuccessListener(aVoid -> Log.d("ViewPharmaceuticals", "Realtime Database updated with new quantity"))
                    .addOnFailureListener(e -> Log.e("ViewPharmaceuticals", "Error updating Realtime Database", e));
        }
    }

 

I want to modify the same value instead of adding a new field. I tried so many ways to do this but every attempt was useless.