用java.util.Observable实现Observer模式

本文转载自：dada360778512的博客

原文链接：http://blog.csdn.net/dada360778512/article/details/6977758

Observer模式  主要是观察者与被观察者之间的关系

观察者为羊，被观察者为狼  模仿的场景为狼叫羊跑

代码如下：

1.被观察者类

package test.pattern.observer;


import java.util.Observable;


public class Wolf extends Observable{

    private String name;


    Wolf(String name) {
        this.name = name;
    }

    public void cry(String state){
        System.out.println(this.getName()+ " crying ");
        this.setChanged();
        this.notifyObservers(state);
    }


    public String getName() {
        return name;
    }


    public void setName(String name) {
        this.name = name;
    }

}

 

2.观察者类

package test.pattern.observer;


import java.util.Observable;
import java.util.Observer;


public class Sheep implements Observer {

    private String state = "eating";
    private String name;

    public Sheep(String name){
        this.name = name;
    }

    public void update(Observable o, Object arg) {
        // TODO Auto-generated method stub
        Wolf wolf = (Wolf)o;
        System.out.println(wolf.getName()+" crying and "+arg+" "+this.getName()+" running.....");
        setState("running");
    }


    public String getState() {
        return state;
    }


    public void setState(String state) {
        this.state = state;
    }


    public String getName() {
        return name;
    }


    public void setName(String name) {
        this.name = name;
    }


}

 

3.测试

package test.pattern.observer;




public class TestObserver {


    public static void main(String[] args) {
        Wolf wolf = new Wolf("wolf1");
        Sheep sheep1 = new Sheep("sheep1");
        Sheep sheep2 = new Sheep("sheep2");
        Sheep sheep3 = new Sheep("sheep3");
        //注册观察者,sheep1,sheep2加入，sheep3未加入
        wolf.addObserver(sheep1);
        wolf.addObserver(sheep2);
        String wolfStat = "hungry";
        //wolf begin cry
        wolf.cry(wolfStat);
    }
}

 

4.结果：

wolf1 crying 
wolf1 crying and hungry sheep2 running.....
wolf1 crying and hungry sheep1 running.....