code: public void modifyOrder(KiteConnect kiteConnect) throws KiteException, IOException {
          // Order modify request will return order model which will contain only order_id.
          OrderParams orderParams =  new OrderParams();
          orderParams.quantity = 1;
          orderParams.orderType = Constants.ORDER_TYPE_LIMIT;
          orderParams.tradingsymbol = "ASHOKLEY";
          orderParams.product = Constants.PRODUCT_CNC;
          orderParams.exchange = Constants.EXCHANGE_NSE;
          orderParams.transactionType = Constants.TRANSACTION_TYPE_BUY;
          orderParams.validity = Constants.VALIDITY_DAY;
          orderParams.price = 122.25;
  
          Order order21 = kiteConnect.modifyOrder("180116000984900", orderParams, Constants.VARIETY_REGULAR);
          System.out.println(order21.orderId);
      }
docs: Modify order.