试题六

阅读以下说明和Java代码，填补代码中的空缺，将解答填入答题纸的对应栏。

    [说明]

    在股票交易中，股票代理根据客户发出的股票操作指示进行股票的买卖操作。其类图如下图所示。相应的Java代码附后。

 类图

    [Java代码]

    import Java.util.ArrayList;

    import java.util.List;

    ClaSS Stock{

    private String name;

    private int quantity;

    public Stock(String name,int quantity){

    thiS.name=name;this.quantity=quantity;

    }

    public void buy（ ）{  System.out.println("[买进]:"+name+",数量:"

    +quantity);}

    public void sell（ ） {System.out.println("[卖出]:"+name+",数量:"

    +quantity);}

    }

    interface Order {

    VOid execute（ ）;

    }

    class BuyStock __（ ）____ Order {

    private Stock stock;

    public BuyStock(Stock stock){___（ ）___=stock;  }

    public void execute（ ）{    stock.buy（ ）;  }

    }

    //类SellStock实现和BuyStock类似,略

    clasS Broker{

    private List＜Order＞orderList=new ArrayList＜Order＞（ ）;

    Dublic void takeOrder(__（ ）____ order){  orderList.add(order);    }

    public void placeOrders（ ）{

    for {_（ ）_____ order:orderList) {order.execute（ ）;  }

    orderLiSt.clear（ ）;

    }

    }

    public class StockCommand {

    public static void main(String[]args){

    Stock aStock:new Stock("股票A",10);

    Stock bStock=new Stock("股票B",20);

    Order buyStockorder=new BuyStock(aStock);

    Order sellStockOrder=new SellSt0Ck(bStoCk);

    Broker broker=new Broker（ ）;

    broker.takeOrder(buyStockorder);

    broker.takeOrder(sellStockOrder);

    broker.__（ ）____;

    }

    }