23种设计模式之装饰者模式

1.定义：

在不必改变原类文件和使用继承的情况下，动态地扩展一个对象的功能。它是通过创建一个包装对象，也就是装饰来包裹真实的对象。

2.设计原则：

1. 多用组合，少用继承。

利用继承设计子类的行为，是在编译时静态决定的，而且所有的子类都会继承到相同的行为。然而，如果能够利用组合的做法扩展对象的行为，就可以在运行时动态地进行扩展。

2. 类应设计的对扩展开放，对修改关闭。

3.UML类图

4.实例代码：

抽象类 Brid

package desiner23.Decorator;public interface Brid {public int fly();}

实体类1 鸟1号，现在可飞50m

package desiner23.Decorator;public class Brid1 implements Brid {public int flyInstance = 50;public Brid1(int flyInstance) {super();this.flyInstance = flyInstance;}public int getFlyInstance() {return flyInstance;}public void setFlyInstance(int flyInstance) {this.flyInstance = flyInstance;}@Overridepublic int fly() {// TODO Auto-generated method stubreturn this.flyInstance;}}

鸟2号

package desiner23.Decorator;public class Brid2 implements Brid {private int flydistance ;public Brid2(int flydistance) {super();this.flydistance = flydistance;}@Overridepublic int fly() {// TODO Auto-generated method stubreturn this.flydistance;}}

装饰抽象类 BridDecoratorAbs

package desiner23.Decorator;public class BridDecoratorAbs implements Brid {public Brid brid;public  int addFlyDistance;public BridDecoratorAbs(){}public BridDecoratorAbs(Brid brid, int addFlyDistance) {super();this.brid = brid;this.addFlyDistance = addFlyDistance;}@Overridepublic int fly() {// TODO Auto-generated method stubreturn 0;}}

装饰实例1 

package desiner23.Decorator;public class BridDecoratorOne extends BridDecoratorAbs {//private int addFlyDistance;public BridDecoratorOne(){}public BridDecoratorOne(Brid brid,int addFlyDistance){this.brid= brid;this.addFlyDistance = addFlyDistance;}@Overridepublic int fly() {return this.brid.fly()+this.addFlyDistance;}}

装饰实例2

package desiner23.Decorator;public class BridDecoratorTwo extends BridDecoratorAbs {public BridDecoratorTwo() {super();// TODO Auto-generated constructor stub}public BridDecoratorTwo(Brid brid, int addFlyDistance) {super(brid, addFlyDistance);// TODO Auto-generated constructor stub}@Overridepublic int fly() {return this.brid.fly()+this.addFlyDistance;}}

测试

package desiner23.Decorator;public class Testr {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubBrid brid1 = new Brid1(20);Brid brid2 = new Brid2(25);Brid brid3 = new BridDecoratorOne(brid1,24);Brid brid4 = new BridDecoratorTwo(brid2,50);Brid brid5= new BridDecoratorTwo(brid3,50);System.out.println(brid3.fly());System.out.println(brid4.fly());System.out.println(brid5.fly());}}

输出：

44
75
94