觀察者模式2

Java內置的觀察者模式如何運做

** 注意：Observable,Observer是java.util.*包裏的 **

氣象數據

package com.example.demo4.tends;

import java.util.Observable;

public class WeatherDate extends Observable{
    private float temperature;
    private float humidity;
    private float pressure;

    public WeatherDate(){

    }
    public void measurementsChanged(){//測量值改變
        setChanged();
        notifyObservers();
    }
    public void setMeasurements(float temperature,float humidity,float pressure){//設置測量值
        this.temperature=temperature;
        this.humidity=humidity;
        this.pressure=pressure;
        measurementsChanged();
    }

    public float getTemperature() {
        return temperature;
    }

    public float getHumidity() {
        return humidity;
    }

    public float getPressure() {
        return pressure;
    }
}

顯示當前條件

package com.example.demo4.tends;

import com.example.demo4.face.DisPlayElement;
import java.util.Observable;
import java.util.Observer;

public class CurrentConditionsDisplay implements Observer,DisPlayElement {
    Observable observable;
    private float temperature;
    private float humidity;
    private float pressure;

    public CurrentConditionsDisplay(Observable observable){
        this.observable=observable;
        observable.addObserver(this);
    }

    @Override
    public void update(Observable observable, Object object) {
        if(observable instanceof WeatherDate){
            this.temperature=((WeatherDate) observable).getTemperature();
            this.humidity=((WeatherDate) observable).getHumidity();
            this.pressure=((WeatherDate) observable).getPressure();
            display();
        }
    }

    @Override
    public void display() {
        System.out.println("Current conditions: "+temperature+"F degrees and "+humidity+"% humidity");
    }
}

測試類

package com.example.demo4.main;

import com.example.demo4.tends.CurrentConditionsDisplay;
import com.example.demo4.tends.WeatherDate;

public class WeatherStation {
    public static void main(String[] args) {
        WeatherDate weatherDate=new WeatherDate();
        weatherDate.setMeasurements(80,81,82);
        CurrentConditionsDisplay ccd=new CurrentConditionsDisplay(weatherDate);
        ccd.update(weatherDate,null);
    }
}