public static void main(string[] args)
        {
            StockTrade     stock     = new StockTrade();
            BuyStockOrder  buystock  = new BuyStockOrder(stock);
            SellStockOrder sellstock = new SellStockOrder(stock);

            Agent agent = new Agent();

            agent.placeOrder(buystock); // Buy Shares
            agent.placeOrder(buystock); // Sell Shares
        }
 public SellStockOrder(StockTrade st)
 {
     stock = st;
 }
 public BuyStockOrder(StockTrade st)
 {
     stock = st;
 }