装饰模式的目的是为了给一个对象动态的增加一些功能。装饰对象和被装饰的对象实现同一个接口，装饰对象持有被装饰对象的实例。
类图：
示意性代码：
package com.javadesignpattern.Decorator; public interface Component { void sampleOperation(); }
package com.javadesignpattern.Decorator; public class ConcreteComponent implements Component{ public void sampleOperation() { // TODO Auto-generated method stub System.out.println(ConcreteComponent.class + ": sampleOperation function"); } }
package com.javadesignpattern.Decorator; public class Decorator implements Component{ Component component; public Decorator(Component component){ this.component = component; } public void sampleOperation() { // TODO Auto-generated method stub component.sampleOperation(); System.out.println(Decorator.class + " : sampleOperation function"); } }
package com.javadesignpattern.Decorator; public class ConcreteDecorator extends Decorator{ Decorator dec; public ConcreteDecorator(Decorator dec){ super(dec.component); this.dec = dec; } public void sampleOperation(){ super.sampleOperation(); System.out.println(ConcreteDecorator.class + " : sampleOperation function"); } }
package com.javadesignpattern.Decorator; public class Client { public static void main(String[] ags){ Component componemt = new Decorator(new ConcreteComponent()); componemt.sampleOperation(); System.out.println("--------------------"); Component componemt1 = new ConcreteDecorator(new Decorator(new ConcreteComponent())); componemt1.sampleOperation(); System.out.println("--------------------"); } }
装饰模式以这样的形式出现：
new Decorator1(new Decorator2(new Decorator3(new ConcreteComponent())))
装饰模式在什么场景下使用：
1. 需要扩展一个类的功能
2. 动态的给一个对象增加一些功能
3. 需要一些扩展类的功能，但是有很多类，这样使得继承变得不太现实。
设计模式（八） ： 结构型模式－－装饰模式,布布扣,bubuko.com
原文：http://www.cnblogs.com/ChristyorRuth/p/3763393.html