[Java知识库]设计模式之观察者模式demo

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代码

public class WeatherData {
    private float temperature;
    private float pressure;
    private float humidity;
    //聚合
    private CurrentConditions currentConditions;

    public WeatherData(CurrentConditions currentConditions) {
        this.currentConditions = currentConditions;
    }

    public float getTemperature() {
        return temperature;
    }

    public float getPressure() {
        return pressure;
    }

    public float getHumidity() {
        return humidity;
    }

    public void dataChange(){
        currentConditions.update(getTemperature(),getPressure(),getHumidity());
    }

    //当数据有更新时候
    public void setData(float temperature, float pressure, float humidity) {
        this.temperature = temperature;
        this.pressure = pressure;
        this.humidity = humidity;
        dataChange();
    }
}

//显示当前天气情况，可以理解成是气象站自己的网站
public class CurrentConditions {
    //温度
    private float temperature;
    //气压
    private float pressure;
    //湿度
    private float humidity;

    //更新天气情况，是由WeatherDate来调用的，使用推送模式
    public void  update(float temperature, float pressure, float humidity) {
        this.temperature = temperature;
        this.pressure = pressure;
        this.humidity = humidity;
        display();
    }

    public void display(){
        System.out.println("temperature" + temperature);
        System.out.println("pressure" + pressure);
        System.out.println("humidity" + humidity);
    }
}

public class Client {
    public static void main(String[] args) {
        //创建接入方CurrentConditions
        CurrentConditions currentConditions = new CurrentConditions();
        //创建weatherData 并将接入方currentConditions 传递到WeatherData中
        WeatherData weatherData = new WeatherData(currentConditions);
        //更新天气情况
        weatherData.setData(30,150,40);
    }
}

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//观察者接口，有观察者来实现
public interface Observer {
    void  update(float temperature,float pressure,float humidity);
}

//观察者
public class CurrentConditions  implements Observer{
    //温度
    private float temperature;
    //气压
    private float pressure;
    //湿度
    private float humidity;

    public void display(){
        System.out.println("temperature" + temperature);
        System.out.println("pressure" + pressure);
        System.out.println("humidity" + humidity);
    }

    @Override
    public void update(float temperature, float pressure, float humidity) {
        this.temperature = temperature;
        this.pressure = pressure;
        this.humidity = humidity;
        display();
    }
}

public class BaiduSite implements Observer{
    //温度
    private float temperature;
    //气压
    private float pressure;
    //湿度
    private float humidity;

    public void display(){
        System.out.println("百度temperature" + temperature);
        System.out.println("百度pressure" + pressure);
        System.out.println("百度humidity" + humidity);
    }

    @Override
    public void update(float temperature, float pressure, float humidity) {
        this.temperature = temperature;
        this.pressure = pressure;
        this.humidity = humidity;
        display();
    }
}

public interface Subject {
    void registerObserver(Observer observer);
    void removeObserver(Observer observer);
    void notifyObserver();
}

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public class WeatherData implements Subject{
    private float temperature;
    private float pressure;
    private float humidity;
    private List<Observer> observerList;

    public WeatherData() {
        observerList = new ArrayList<>();
    }

    public float getTemperature() {
        return temperature;
    }

    public float getPressure() {
        return pressure;
    }

    public float getHumidity() {
        return humidity;
    }

    public void dataChange(){
        notifyObserver();
    }

    //当数据有更新时候
    public void setData(float temperature, float pressure, float humidity) {
        this.temperature = temperature;
        this.pressure = pressure;
        this.humidity = humidity;
        dataChange();
    }

    //新增观察者
    @Override
    public void registerObserver(Observer observer) {
        observerList.add(observer);
    }

    //删除观察者
    @Override
    public void removeObserver(Observer observer) {
        observerList.remove(observer);
    }

    //遍历所有的观察者，并通知
    @Override
    public void notifyObserver() {
        observerList.forEach(e->{
            e.update(temperature,pressure,humidity);
        });
    }
}

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public class Client {
    public static void main(String[] args) {
        //创建一个WeatherData
        WeatherData weatherData = new WeatherData();
        //创建一个观察者
        CurrentConditions currentConditions = new CurrentConditions();
        BaiduSite baiduSite = new BaiduSite();


        //注册到weatherData
        weatherData.registerObserver(currentConditions);
        weatherData.registerObserver(baiduSite);
        weatherData.setData(10,100,30);

    }
}