This code ensures that duplicate data will not be in rv list.

adding new data to rv checking duplicate

    public void addAll(ArrayList<Inventory> newList) {
        // Lg.i(TAG, "Adding all: Current count=" + c + ", \nNew count=" + newList.size());
        //Previous List of Recycler View
        List<Inventory> itemList = this.itemList;
        for (Inventory iv : newList) {
            boolean exists = false;
            // id of new list
            int id = iv.getId();
            for (Inventory ivOld : itemList)
                // checking new id with old id
                if (id == ivOld.getId()) {
                // if exists then don't need to add
                    exists = true;
                    break;
                }
            if (!exists) {
            // if not exists, then we are adding it to the rv list
                this.itemList.add(iv);
                notifyItemInserted(this.itemList.size() - 1);
            }
        }
    }