protected boolean AddInventory(Inventory inventory) throws NullPointerException{
        if (null == Inventory.libraryMaterials) {
            return false;
        }
        try{
            if (Inventory.libraryMaterials.containsKey(Inventory.libraryMaterialID)) {
                return false;
            }
            Inventory.libraryMaterials.put(Inventory.libraryMaterialID, this);
            return true;
        }
        catch(NullPointerException ex){
            throw ex;
        }
    }