Observer

最新推荐文章于 2022-08-15 09:30:00 发布

最新推荐文章于 2022-08-15 09:30:00 发布 · 95 阅读

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本文介绍了一个基于Java的观察者模式实现案例。通过House类作为被观察对象，ZhangSan、LiSi和WangWu类作为观察者，演示了一对多的依赖关系。当House的价格发生变化时，所有观察者都将自动更新。

观察者模式定义了对象之间的一对多依赖,这样一来,当一个对象改变状态时,它的所有依赖者都会收到通知并自动更新。

下面是House.java的代码：

package com.flyingh.observable;

import java.util.Observable;

public class House extends Observable {
	private float price;

	public House() {
		super();
	}

	public House(float price) {
		super();
		this.price = price;
	}

	public float getPrice() {
		return price;
	}

	public void setPrice(float price) {
		this.price = price;
		setChanged();
		notifyObservers(price);
	}
}

下面是观察者ZhangSan.java的代码：

package com.flyingh.observer;

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

public class ZhangSan implements Observer {
	private Observable house;

	public ZhangSan(Observable house) {
		super();
		this.house = house;
		house.addObserver(this);
	}

	public Observable getHouse() {
		return house;
	}

	public void setHouse(Observable house) {
		this.house = house;
	}

	@Override
	public void update(Observable o, Object arg) {
		// TODO Auto-generated method stub
		System.out.println("zhangsan:" + arg);
	}

}

下面是观察者LiSi.java的代码：

package com.flyingh.observer;

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

public class LiSi implements Observer {
	private Observable house;

	public LiSi(Observable house) {
		super();
		this.house = house;
		house.addObserver(this);
	}

	public Observable getHouse() {
		return house;
	}

	public void setHouse(Observable house) {
		this.house = house;
	}

	@Override
	public void update(Observable o, Object arg) {
		// TODO Auto-generated method stub
		System.out.println("lisi:" + arg);
	}

}

下面是观察者WangWu.java的代码：

package com.flyingh.observer;

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

public class WangWu implements Observer {
	private Observable house;

	public WangWu(Observable house) {
		super();
		this.house = house;
		house.addObserver(this);
	}

	public Observable getHouse() {
		return house;
	}

	public void setHouse(Observable house) {
		this.house = house;
	}

	@Override
	public void update(Observable o, Object arg) {
		// TODO Auto-generated method stub
		System.out.println("wangwu:" + arg);
	}

}

下面是Client.java的代码：


package com.flyingh.client;

import com.flyingh.observable.House;
import com.flyingh.observer.LiSi;
import com.flyingh.observer.WangWu;
import com.flyingh.observer.ZhangSan;

public class Client {
	public static void main(String[] args) {
		House house = new House(1500);

		new ZhangSan(house);
		new LiSi(house);
		new WangWu(house);

		house.setPrice(2000);
	}
}

程序运行结果如下：

wangwu:2000.0
lisi:2000.0
zhangsan:2000.0