java实现观察者模式

package cn.demo;

public class TestObersver {
	public static void main(String[] args) {
		Person person=new Person();		//声明被观察者
		System.err.println("person:"+person);
		person.addPersonListener(new PersonListener(){
			public void running(PersonEvent pe) {
				System.err.println("正在观察的人："+pe.getSource());
				System.err.println("他正在跑步");
			}
		});
		person.run();
	}
}

class Person{
	private PersonListener pl;
	public void addPersonListener(PersonListener pl){
		this.pl=pl;
	}
	
	public void run(){
		if(pl!=null){
			pl.running(new PersonEvent(this));	
		}
		System.err.println("正在跑步....");
	}
}

interface PersonListener{
	void running(PersonEvent pe);
}

class PersonEvent{
	private Object obj;
	public PersonEvent(Object obj){
		this.obj=obj;
	}
	public Object getSource(){
		return obj;
	}
}