试题五(共15分)
阅读下列说明和C++-代码,将应填入 (n) 处的字句写在答题纸的对应栏内。
【说明】
某发票(lnvoice)由抬头(Head)部分、正文部分和脚注(Foot)部分构成。现采用装饰(Decorator)模式实现打印发票的功能,得到如图5-1所示的类图。
【C++代码】
include <iostream>
using namespace std;
class invoice{
public:
(1) {
cout《 "This is the content of the invoice!"《 endl;
}
};
class Decorator : public invoice {
Invoice *ticket;
public:
Decorator(lnvoice *t) { ticket = t; }
void printinvoice(){
if(ticket != NULL)
(2);
}
};
class HeadDecorator : public Decorator{
public:
HeadDecorator(lnvoice*t): Decorator(t) { }
void printinvoice0 {
cout《 "This is the header of the invoice! "<< endl;
(3) ;
}
};
class FootDecorator : public Decorator{
public:
FootDecorator(invoice *t): Decorator(t) { }
void printlnvoice() {
(4) ;
cout《 "This is the footnote of the invoice!"《 endl;
}
};
int main(void) {
Invoice t;
FootDecorator f(&t);
HeadDecorator h(&f);
H.printlnvoice();
cout< < “_____”< < endl;
FootDecorator a(NULL);
HeadDecorator b((5) );
B.printinvoice();
return 0;
}
程序的输出结果为:
This is the header of the invoice!
This is the content of the invoice!
This is the footnote of the invoice!
----------------------------
This is the header of the invoice!
This is the footnote of the invoice!