装饰者模式

来源：互联网发布：金枝玉叶电影知乎编辑：程序博客网时间：2024/06/05 00:39

装饰者模式的实现：装饰者模式是在不必改变原类文件和使用继承的情况下，动态扩展一个对象的功能，它是通过创建一个包装对象，来装饰和包裹真实的对象。
优点：装饰者模式和继承关系都是要扩展对象的功能，但装饰者模式可以提供比继承更多的灵活性。
缺点：灵活性是更好了，却增加了对象的复杂性

装饰者模式会导致设计中出现许多小类，如果过度使用，会使程序变得很复杂。

还是举个例子比较容易理解：

1.创建IthirdParty接口

package decorator;/** * 抽象类接口 * @author lyh * */public interface IthirdParty {public String sayMsg();}

2.创建IthirdParty接口的实现类 ThirdParty

package decorator;/** * 具体类 * @author lyh * */public class ThirdParty implements IthirdParty{@Overridepublic String sayMsg() {return "Hello";}}

3.创建ThirdParty的装饰类Decorator1，也实现IthirdParty接口

package decorator;/** * 具体装饰类1 * @author lyh * */public class Decorator1 implements IthirdParty{private IthirdParty thirdParty;public Decorator1(IthirdParty thirdParty){this.thirdParty=thirdParty;}@Overridepublic String sayMsg() {return "##1"+thirdParty.sayMsg()+"##1";}}

4.创建ThirdParty的装饰类Decorator2，也实现IthirdParty接口

package decorator;/** * 具体装饰类2 * @author lyh * */public class Decorator2 implements IthirdParty{private IthirdParty ithirdParty;public Decorator2(IthirdParty ithirdParty){this.ithirdParty=ithirdParty;}@Overridepublic String sayMsg() {return "##2"+ithirdParty.sayMsg()+"##2";}}

5.创建测试类Test

package decorator;/** * @author lyh * */public class Test {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());}}

输出结果是：##2##1Hello##1##2

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