JAVA 装饰模式-2016软件设计师下半年考试真题

题目要求：打印发票头、内容、底部的要求

BTW,八成这次软考又挂了…

class Invoice{
  public void printInvoice(){
    System.out.println("this is content");
  }
}

class Decorator extends Invoice{
  protected Invoice ticket;
  public Decorator (Invoice t){
    ticket=t;
  }
  public void printInvoice(){
    if(ticket!=null){
      ticket.printInvoice();
    }
  }
}

class HeaderDecorator extends Decorator{

  public HeaderDecorator(Invoice t){
    super(t);
  }
  public void printInvoice(){
    System.out.println("this is the header");
    super.printInvoice();
  }

}

class FooterDecorator extends Decorator{

  public FooterDecorator(Invoice t){
    super(t);
  }
  public void printInvoice(){

    super.printInvoice();
    System.out.println("this is the footer");
  }

}



public class zhuangshi {

  public static void main(String[] args){
    Invoice t =new Invoice();
    Invoice ticket;
    ticket=new FooterDecorator(new HeaderDecorator(t));
    ticket.printInvoice();
    System.out.println("=====================");
    ticket=new FooterDecorator(new HeaderDecorator(new Decorator(null)));
    ticket.printInvoice();
  }

}

这么写也行 ，不知道哪个算标准答案

Invoice t =new Invoice();
 Invoice ticket;
 ticket=new HeaderDecorator(new FooterDecorator(t));
 ticket.printInvoice();
 System.out.println("=====================");
 ticket=new HeaderDecorator(new FooterDecorator(null));
 ticket.printInvoice();

结果