观察者模式

观察者模式

一个对象状态改变，可以引起多个对象的状态改变

Subject  抽象主题

Observer 抽象观察者

Boiler 具体主题

LED 具体观察者

Client   测试例子

package com.moreas.design;

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

public abstract class Subject{
	
	   private List<Observer> observers = new ArrayList<Observer>();

	    //添加观察者
	    public void attach(Observer observer) {
	        observers.add(observer);
	    }

	    //移除观察者
	    public void tach(Observer observer) {
	        observers.remove(observer);
	    }

	    //通知所有的被观察者
	    public void notice(Subject subject){
	        for (Observer obj: observers) {
	            obj.update(subject);
	        }
	    }
	
 
}

　　

package com.moreas.design;

public abstract class  Observer {
	
	 public abstract void update(Subject subject);
}

　　

package com.moreas.design;
public class Boiler extends Subject {
    //水温
    public int temperature;

    /**烧水*/
    public void onBoil(){
        for(int i=0;temperature<100;i++){
            temperature=temperature+1;  //升温
            super.notice(this);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

　　

package com.moreas.design;
public class LED extends Observer {
    @Override
    public void update(Subject subject) {
        Boiler boiler = (Boiler) subject;
        System.out.println("当前水温：" + boiler.temperature);
    }
}

　　

package com.moreas.design;
public class Client {
    public static void main(String[] args) {
        //观察者
       // Observer alarm=new Alarm();
        Observer led=new LED();

        //主题
        Boiler boiler=new Boiler();
       // boiler.attach(alarm);
        boiler.attach(led);

        //烧水
        boiler.onBoil();
    }
}

　　

 观察者模式，简单改动

public class Subject {

    private List<Observer> observers = new ArrayList<>();

    private int state;

    public int getState() {
        return this.state;
    }

    public void setState(int state) {
        if (state == this.state) {
            return;
        }
        this.state = state;
        notifyAllObserver();
    }

    public void attach(Observer observer) {
        observers.add(observer);
    }

    private void notifyAllObserver() {
        observers.stream().forEach(x -> x.update());
    }
}

public abstract class Observer {

    protected Subject subject;

    public Observer(Subject subject) {
        this.subject = subject;
        this.subject.attach(this);
    }

    public abstract void update();

}

public class BinaryObserver extends Observer {

    public BinaryObserver(Subject subject) {
        super(subject);
    }

    @Override
    public void update() {
        System.out.println("Binary String:" + Integer.toBinaryString(subject.getState()));
    }
}

//Octal  八进制
public class OctalObserver extends Observer {

    public OctalObserver(Subject subject) {
        super(subject);
    }

    @Override
    public void update() {
        System.out.println("Octal String:" + Integer.toOctalString(subject.getState()));
    }
}

public class  Client {
    public static void main(String[] args) {

        final Subject subject = new Subject();
        new BinaryObserver(subject);
        new OctalObserver(subject);
        System.out.println("==================");
        subject.setState(10);
        
        System.out.println("==================");
        subject.setState(10);

        System.out.println("==================");
        subject.setState(15);
    }
}