public ProductList getProductList(String prod_desc)
    {
        if(prod_desc.isEmpty())
        {
            letter = true;
            return null;
        }
        else
        {
            max_index = prod_desc.length();       // Check number of symbols
            prod_id_num = 0;
            if((prod_desc.charAt(0) < '0')||(prod_desc.charAt(0) > '9'))
            {
                    // First symbol is not a digit
                    letter = true;
            }
            else
            {
                    letter = false;
            }

            for(index = 0; index < max_index; index++)
            {
                // convert input to Integer
                prod_id_num += prod_id_num*10 + prod_desc.charAt(index) - '0';
            }
            
            if(letter == true)
            {
                return searchByProductDesc(prod_desc);
            }
            else
            {
                return searchByProductID(String.valueOf(prod_id_num));
            }
        }    
    }