观察者模式（转）

原文链接： http://blog.csdn.net/yongh701/article/details/49613587

看类图知道ConcreteSubject与ConcreteObserver分别实现Subject与Observer两个接口，因为其继承线段是虚线
同时观察者与主题之间是关联关系，也就是说观察者类中必有主题这个类成员，主题类中必有观察者这个类成员

相关题目：
某实验室欲建立一个实验室的环境监测系统，能够显示实验室的温度、湿度以及洁净度等环境数据，当获取到最新的环境测量数据时，显示的环境数据能够更新，现在采用观察者（Observer）模式来开发该系统
具体代码：

package kunpu.plandesign.observe;

/**
 * @author zhen
 */
public interface Subject {
    /**
     * 注册观察者
     * @param observer
     */
    public void registerObserve(Observer observer);

    /**
     * 删除观察者
     * @param observer
     */
    public void removeObserve(Observer observer);

    /**
     * 通知观察者
     */
    public void notifyObserves();
}


package kunpu.plandesign.observe;

/**
 * @author zhen
 */
public interface Observer {

    /**
     * 观察操作
     * @param temp 温度
     * @param humidity 湿度
     * @param cleanness 清洁度
     */
    public void update(float temp, float humidity, float cleanness);

}


package kunpu.plandesign.observe;

import java.util.ArrayList;

/**
 * @author zhen
 * 环境数据
 */
public class EnvironmentData implements Subject{
    private ArrayList<Observer> observers;
    private float temp;
    private float humidity;
    private float cleanness;

    public EnvironmentData() {
        observers = new ArrayList<>();
    }

    /**
     * 设置测量值
     * @param temp
     * @param humidity
     * @param cleanness
     */
    public void setMeasurements(float temp, float humidity, float cleanness){
        this.temp = temp;
        this.humidity = humidity;
        this.cleanness = cleanness;
        notifyObserves();
    }


    @Override
    public void registerObserve(Observer observer) {
        observers.add(observer);
    }

    @Override
    public void removeObserve(Observer observer) {
        observers.remove(observer);
    }

    @Override
    public void notifyObserves() {
        observers.forEach(observer -> {
            observer.update(getTemp(), getHumidity(), getCleanness());
        });
    }

    public ArrayList<Observer> getObservers() {
        return observers;
    }

    public void setObservers(ArrayList<Observer> observers) {
        this.observers = observers;
    }

    public float getTemp() {
        return temp;
    }

    public void setTemp(float temp) {
        this.temp = temp;
    }

    public float getHumidity() {
        return humidity;
    }

    public void setHumidity(float humidity) {
        this.humidity = humidity;
    }

    public float getCleanness() {
        return cleanness;
    }

    public void setCleanness(float cleanness) {
        this.cleanness = cleanness;
    }
}


package kunpu.plandesign.observe;

import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * @author zhen
 */
public class CurrentConditionDisplay implements Observer {
    private String name;
    private Subject envData;
    private float temp;
    private float humidity;
    private float cleanness;

    @Override
    public void update(float temp, float humidity, float cleanness) {
        this.temp = temp;
        this.humidity = humidity;
        this.cleanness = cleanness;
    }

    public void display(){
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String date = sdf.format(new Date());
        System.out.println("我是" + name + "，时间：" + date + "，温度：" + temp + "、湿度：" + humidity + "、清洁度：" + cleanness + "。" );
    }

    public CurrentConditionDisplay(String name, Subject envData) {
        this.name = name;
        this.envData = envData;
        envData.registerObserve(this);
    }

    public String getName() {
        return name;
    }

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

    public Subject getEnvData() {
        return envData;
    }

    public void setEnvData(Subject envData) {
        this.envData = envData;
    }

    public float getTemp() {
        return temp;
    }

    public void setTemp(float temp) {
        this.temp = temp;
    }

    public float getHumidity() {
        return humidity;
    }

    public void setHumidity(float humidity) {
        this.humidity = humidity;
    }

    public float getCleanness() {
        return cleanness;
    }

    public void setCleanness(float cleanness) {
        this.cleanness = cleanness;
    }
}

package kunpu.plandesign.observe;

/**
 * @author zhen
 * 环境监控
 */
public class EnvironmentMonitor {

    public static void main(String[] args) {
        EnvironmentData environmentData = new EnvironmentData();
        CurrentConditionDisplay currentConditionDisplay = new CurrentConditionDisplay("观察者1", environmentData);
        CurrentConditionDisplay currentConditionDisplay1 = new CurrentConditionDisplay("观察者2", environmentData);
        environmentData.setMeasurements(12, 34, 52.3f);
        currentConditionDisplay.display();
        currentConditionDisplay1.display();

    }

}