观察者模式

观察者模式　-  在对象之间定义一对多的依赖,这样一来,当一个对象改变状态,依赖他的对象都会收到通知,并更新

/**
 * @description 观察者 更新消息
 */
public interface Observer {
    /**
     * 功能描述: 更新
     * @author a
     * @date 14:53 2020/11/23
     * @param temp
     * @param humidity
     * @param pressure
     */
    void update(float temp, float humidity, float pressure);
}

　　

package com.design.demo5;

/**
 * @description 主题
 */
public interface Subject {

    /**
     * 功能描述: 添加观察者
     * @param observer 观察者对象
     */
    void registerObserver(Observer observer);


    /**
     * 功能描述: 删除观察者
     * @param observer 观察者对象
     */
    void removeObserver(Observer observer);

    /**
     * 功能描述: 通知观察者
     */
    void notifyObserver();
}

　　

package com.design.demo5;

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

/**
 * @description 天气数据 改变气象数据 通知观察者
 */
public class WeatherData implements Subject {

    private List<Observer> observers;
    private float temperature;
    private float humidity;
    private float pressure;

    public WeatherData() {
        this.observers = new ArrayList<>();
    }

    //改变气象数据
    public void setMeasurements(float temperature, float humidity, float pressure) {
        // 更改气象数据
        this.temperature = temperature;
        this.humidity = humidity;
        this.pressure = pressure;
        // 通知观察者
        measurementsChanged();
    }

    private void measurementsChanged() {
        notifyObserver();
    }

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

    @Override
    public void removeObserver(Observer observer) {
        int i = observers.indexOf(observer);
        if (i >= 0) {
            observers.remove(i);
        }
    }

    @Override
    public void notifyObserver() {
        for (Observer observer : observers) {
            observer.update(temperature, humidity, pressure);
        }
    }

    public float getTemperature() {
        return temperature;
    }

    public void setTemperature(float temperature) {
        this.temperature = temperature;
    }

    public float getHumidity() {
        return humidity;
    }

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

    public float getPressure() {
        return pressure;
    }

    public void setPressure(float pressure) {
        this.pressure = pressure;
    }
}

　　

package com.design.demo5;

/**
 * @description 观察者对象
 */
public class ObserverTest01 implements Observer {

    private float temperature;
    private float humidity;
    private float pressure;
    private WeatherData weatherData;

    public ObserverTest01(WeatherData weatherData) {
        this.weatherData = weatherData;
        //订阅
        weatherData.registerObserver(this);
    }
    @Override
    public void update(float temp, float humidity, float pressure) {
        this.temperature = temp;
        this.humidity = humidity;
        this.pressure = pressure;
        display();
    }
    public void display() {
        System.out.println("[push] 当前温度01:" + temperature + " 当前湿度01: " + humidity + " 当前压力01:" + pressure);
    }
}
public class ObserverTest02 implements Observer {

    private float temperature;
    private float humidity;
    private float pressure;
    private WeatherData weatherData;

    public ObserverTest02(WeatherData weatherData) {
        this.weatherData = weatherData;
        //订阅
        weatherData.registerObserver(this);
    }
    @Override
    public void update(float temp, float humidity, float pressure) {
        this.temperature = temp;
        this.humidity = humidity;
        this.pressure = pressure;
        display();
    }
    public void display() {
        System.out.println("[push] 当前温度02:" + temperature + " 当前湿度02: " + humidity + " 当前压力02:" + pressure);
    }
}

　　

public class Test {
    public static void main(String[] args) {
        WeatherData weatherData = new WeatherData();
        ObserverTest01 observerTest01 = new ObserverTest01(weatherData);
        ObserverTest02 observerTest02 = new ObserverTest02(weatherData);
        weatherData.setMeasurements(36, 56, 99);
    }
}

//[push] 当前温度01:36.0 当前湿度01: 56.0 当前压力01:99.0
//[push] 当前温度02:36.0 当前湿度02: 56.0 当前压力02:99.0