试题详情

阅读下列说明和java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6-1所示的类图。 【java代码】 class invoice{ public void printInvoice（ ）{ System.out.println ( "This is the content of the invoice!"); } } class Decorator extends Invoice { protected Invoice ticket; public Decorator(lnvoice t){ ticket = t; } public void printInvoice（ ）{ if(ticket != null) （1） ; } } class HeadDecorator extends Decorator{ public HeadDecorator(lnvoice t){ super(t); } public void printInvoice （ ）{ Systent.out.println( "This is the header of the invoice! "); （2） ; } } class FootDecorator extends Decorator { public FootDecorator(Invoice t){ super(t); } public void printlnvoice（ ）{ （ 3） ; Systent.out.println( "This is the footnote of the invoice! "); } } Class test { public static void main(String[] args){ Invoice t =new Invioce（ ）; Invoice ticket; ticket= （4） ; ticket.printInvoice（ ）; Systent.out.println(“------------------“); ticket= （5） ; ticket.printInvoice（ ）; } } 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!