閱讀下列說(shuō)明和C++代碼，填補(bǔ)代碼中的空缺，將解答填入答題紙的對(duì)應(yīng)欄內(nèi)。
【說(shuō)明】
以下C++代碼實(shí)現(xiàn)一個(gè)簡(jiǎn)單客戶(hù)關(guān)系管理系統(tǒng)（CrM）中通過(guò)工廠(chǎng)（Customerfactory）對(duì)象來(lái)創(chuàng)建客戶(hù)（Customer）對(duì)象的功能?？蛻?hù)分為創(chuàng)建成功的客戶(hù)（realCustomer）和空客戶(hù)（NullCustomer）?？湛蛻?hù)對(duì)象是當(dāng)不滿(mǎn)足特定條件時(shí)創(chuàng)建或獲取的對(duì)象。類(lèi)間關(guān)系如圖6-1所示。

【C++代碼】
#include
#include
using namespace std;

class Customer｛
protected:
string name;
public:
（   1   ） boll isNil()=0;
（   2   ） string getName()=0;
﹜;

class RealCustomer (   3   )｛
Public:
realCustomer(string name)｛this->name=name;﹜
bool isNil()｛ return false;  ﹜
string getName()｛ return name;  ﹜
﹜;
class NullCustomer (    4   ) ｛
public:
bool isNil()｛  return true; ﹜
string getName()｛ return 〝Not Available in Customer Database〞; ﹜
﹜;

class Customerfactory｛
public:
string names［3］=｛〝rob〞, 〝Joe〞,〝Julie〞﹜;
public:
Customer*getCustomer(string name)｛
for （int i=0;i<3;i++)｛
if （names[i].(   5   ) )｛
return new realCustomer(name);
﹜
﹜
return (   6   );
﹜
﹜;

class CRM｛
public:
void getCustomer()｛
Customerfactory*(   7   );
Customer*customer1=cf->getCustomer(〝Rob〞);
Customer*customer2=cf->getCustomer(〝Bob〞);
Customer*customer3=cf->getCustomer(〝Julie〞);
Customer*customer4=cf->getCustomer(〝Laura〞);

cout<<〝Customers〞<cout cout cout cout delete cf;
﹜
﹜;
int main()｛
CRM*crs=new CRM();
crs->getCustomer();
delete crs;
return 0;
﹜

/*程序輸出為：
Customers
rob
Not Available in Customer Database
Julie
Not Available in Customer Database
*/