设计模式——观察者模式

package com.wsds.test;

import java.util.ArrayList;
import java.util.List;

/**
 * 抽象主题类
 * @author Administrator
 *
 */
public abstract class Subject {
	//用来保存注冊观察者的对象
	private List<Observer> list = new ArrayList<Observer>();
	
	/**
	 * 注冊观察者对象
	 * @param observer 观察者对象
	 */
	public void attach(Observer observer){
		list.add(observer);
		System.out.println("Attached an obsever");
	}
	
	/**
	 * 删除观察者对象
	 * @param observer 观察者对象
	 */
	public void detach(Observer observer){
		list.remove(observer);
	}
	
	public void notifyObservers(String newState){
		for(Observer observer: list){
			observer.update(newState);
		}
	}
	
	
	
	
	
	
	
	
}

package com.wsds.test;

/**
 * 详细主题角色类
 * @author Administrator
 *
 */
public class ConcreteSubject extends Subject{
	private String state;
	
	public String getState(){
		return state;
	}
	
	public void change(String newState){
		state = newState;
		System.out.println("主题状态为:" + state);
		//状态发生改变，通知各个观察者
		this.notifyObservers(state);
	}
}

package com.wsds.test;

public interface Observer {

	/**
	 * 更新接口
	 * @param state 更新的状态
	 */
	public void update(String state);
}

package com.wsds.test;

public class ConcreteObserver implements Observer{
	
	//观察者状态
	private String observerState;
	
	@Override
	public void update(String state) {
		/*
		 * 更新观察者状态，使其与目标的状态一致
		 */
		observerState = state;
		System.out.println("观察者的状态为:" + state);
	}

}

package com.wsds.test;

public class Client {
	public static void main(String[] args) {
		//创建主题对象
		ConcreteSubject subject = new ConcreteSubject();
		//创建观察者对象
		Observer observer = new ConcreteObserver();
		//将观察者对象注冊到主题对象上
		subject.attach(observer);
		//改变主题对象的状态
		subject.change("new State");
	}
}

package com.wsds.test;

import java.util.ArrayList;
import java.util.List;

/**
 * 抽象主题类
 * @author Administrator
 *
 */
public abstract class Subject {
	//用来保存注冊观察者的对象
	private List<Observer> list = new ArrayList<Observer>();
	
	/**
	 * 注冊观察者对象
	 * @param observer 观察者对象
	 */
	public void attach(Observer observer){
		list.add(observer);
		System.out.println("Attached an obsever");
	}
	
	/**
	 * 删除观察者对象
	 * @param observer 观察者对象
	 */
	public void detach(Observer observer){
		list.remove(observer);
	}
	
	public void notifyObservers(String newState){
		for(Observer observer: list){
			observer.update(this);
		}
	}
}

package com.wsds.test;

/**
 * 详细主题角色类
 * @author Administrator
 *
 */
public class ConcreteSubject extends Subject{
	private String state;
	
	public String getState(){
		return state;
	}
	
	public void change(String newState){
		state = newState;
		System.out.println("主题状态为:" + state);
		//状态发生改变，通知各个观察者
		this.notifyObservers(state);
	}
}

package com.wsds.test;

public interface Observer {

	/**
	 * 更新接口
	 * @param state 更新的状态
	 */
	public void update(Subject subject);
}

package com.wsds.test;

public class ConcreteObserver implements Observer{
	
	//观察者状态
	private String observerState;
	
	@Override
	public void update(Subject subject) {
		/*
		 * 更新观察者状态，使其与目标的状态一致
		 */
		observerState = ((ConcreteSubject) subject).getState();
		System.out.println("观察者的状态为:" + observerState);
	}

}

package com.wsds.test;

import java.util.Observable;

/**
 * 详细主题角色类
 * @author Administrator
 *
 */
public class ConcreteSubject extends Observable{
	private String state;
	
	public String getState(){
		return state;
	}
	
	public void change(String newState){
		state = newState;
		System.out.println("主题状态为:" + state);
		//标记状态改变
		setChanged();
		//状态发生改变，通知各个观察者
		this.notifyObservers(state);
	}
}

package com.wsds.test;

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

public class ConcreteObserver implements Observer{
	
	//观察者状态
	private String observerState;
	
	public ConcreteObserver(Observable o){
		o.addObserver(this);
	}
	

	@Override
	public void update(Observable o, Object arg) {
		/*
		 * 更新观察者状态，使其与目标的状态一致
		 */
		observerState = ((ConcreteSubject) o).getState();
		System.out.println("观察者的状态为:" + observerState);
	}

}