日拱一卒（二十六）

装饰模式：动态地给一个对象增加一些额外的职责，就增加功能来说，装饰模式比生成子类更灵活。

         白话：以人穿衣服鞋子为例，衣服鞋子这些类不是人的属性，但要实现人各种不同的搭配；如果将衣服鞋子的属性放到人这个类，则会使人这个类无比臃肿，此时可以使用装饰的方式：鞋子和衣服类提供装饰方法。当人要装配上衣服时，将人传递给衣服类，让衣服给人装饰上，鞋子亦同。

模式简化：

1. 如果只有一个Concrete Component类而没有抽象的Component接口时，可以让Decorator继承Concrete Component。

2. 如果只有一个Concrete Decorator类时，可以将Decorator和Concrete Decorator合并。

IthirdParty.Java--抽象接口类
=====================
package decorator.saystr;
public interface IthirdParty {
public String sayMsg();
}
ThirdParty.Java--具体类
===================
public class ThirdParty implements IthirdParty {
public String sayMsg() {
　　return "hello";
　　}
}
Decorator1.java 具体装饰类1
==================
package decorator.saystr;
public class Decorator1 implements IThirdParty {
private IThirdParty thirdParty;
public Decorator1(IThirdParty thirdParty){
this.thirdParty= thirdParty;
}
public String sayMsg(){
return "##1"+ thirdParty.sayMsg() + "##1";
}
}
Decorator1.java 具体装饰类2
==================
package decorator.saystr;
public class Decorator2 implements IThirdParty {
private IThirdParty thirdParty;
public Decorator2(IThirdParty thirdParty){
this.thirdParty= thirdParty;
}
public String sayMsg(){
return "##2"+ thirdParty.sayMsg() + "##2";
}
}
MailTest.java
====================
package decorator.saystr;
public class MailTest {
public static void main(String[] args){

　　IthirdParty thirdPartyOne =new ThirdParty();
　　IthirdParty decorator1 =new Decorator1(thirdPartyOne);
　　IthirdParty decorator2 =new Decorator2(decorator1);
　　
　　System.out.println(decorator2.sayMsg());
}
}
执行结果是：##2##1hello##1##2