java设计模式——观察者模式-优快云博客

/*
    主题接口
 */
public interface Subject {
    public void registerObserver(Observer o);
    public void removeObserver(Observer o);
    public void notifyObservers();
}

/*
    主题类
 */
public class WeatherData implements Subject {
    private ArrayList<Observer> obervers;
    private float temperature;
    private float humidity;
    private float pressure;
    public  WeatherData(){
        obervers=new ArrayList<Observer>();
    }
    public void registerObserver(Observer o) {
        obervers.add(o);
    }
    public void removeObserver(Observer o) {
        obervers.remove(o);

    }
    public void notifyObservers() {
        for(Observer o:obervers)
            o.update(temperature,humidity,pressure);
    }
    public void measurementsChanged(){
        notifyObservers();
    }
    public void setMeasurements(float temperature,float humidity,float pressure){
        this.temperature=temperature;
        this.humidity=humidity;
        this.pressure=pressure;
        measurementsChanged();
    }
}

/*
    观察者接口
 */
public interface Observer {
    public void update(float temp,float humidity,float pressure);
}

/*
    布告栏接口
 */
public interface DisplayElement {
    public void display();
}

/*
    观察者类
 */
public class CurrentConditionsDisplay implements Observer,DisplayElement {
    private float temperature;
    private float humidity;
    private float pressure;
    private Subject weatherData;
    public CurrentConditionsDisplay(Subject weatherData){
        this.weatherData=weatherData;
        weatherData.registerObserver(this);
    }
    public void update(float temperature, float humidity, float pressure) {
        this.temperature=temperature;
        this.humidity=humidity;
        this.pressure=pressure;
        display();
    }
    public void display() {
        System.out.println(String.format("temperature:%f\nhumidity:%f\npressure:%f\n",temperature,humidity,pressure));
    }
}

/*
    测试
 */
public class UnitTest {
    @Test
    public void test(){
        WeatherData weatherData=new WeatherData();
        CurrentConditionsDisplay currentConditionsDisplay= new CurrentConditionsDisplay(weatherData);
        weatherData.setMeasurements(10,20,30);
    }
}