观察者模式

观察者模式

观察者接口

//观察者端接口
interface Observer{
    void update(float temperture,float pressure,float humidity);
}

天气预报局接口

//天气预报局接口
interface Subject{
    void registerObserver(Observer observer);
    void removeObserver(Observer observer);
    void notifyObserver();
}

观察者实现类

//一个观察者实现类
class CurrentConditions implements Observer{
    private float temperture;
    private float pressure;
    private float humidity;
    @Override
    public void update(float temperture, float pressure, float humidity) {
        this.temperture = temperture;
        this.pressure = pressure;
        this.humidity = humidity;
        display();
    }

    private void display() {
        System.out.println(temperture);
        System.out.println(pressure);
        System.out.println(humidity);
    }

}

天气预报局实现类

//一个天气预报局实现类
class WeatherData implements Subject{
    private float temperatrue;
    private float pressure;
    private float humidity;
    private ArrayList<Observer> observers;

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

    public float getTemperatrue() {
        return temperatrue;
    }

    public float getPressure() {
        return pressure;
    }

    public float getHumidity() {
        return humidity;
    }
    //通知观察者
    public void dataChange(){
        notifyObserver();
    }
    //更新数据
    public void setData(float temperatrue,float pressure,float humidity){
        this.temperatrue = temperatrue;
        this.pressure = pressure;
        this.humidity = humidity;
        dataChange();
    }
    //添加一个观察者
    @Override
    public void registerObserver(Observer observer) {
        observers.add(observer);
    }
    //移除一个观察者
    @Override
    public void removeObserver(Observer observer) {
        if (observers.contains(observer)) {
            observers.remove(observer);
        }
    }
    //遍历所有观察者通知他们
    @Override
    public void notifyObserver() {
        for (int i =0;i<observers.size();i++){
            observers.get(i).update(getTemperatrue(),getPressure(),getHumidity());
        }
    }
}

测试类

public class ObserverTest {
    public static void main(String[] args) {
        WeatherData weatherData = new WeatherData();
        CurrentConditions currentConditions = new CurrentConditions();
        weatherData.registerObserver(currentConditions);
        weatherData.setData(12.0f,12.0f,12.0f);
        weatherData.setData(16.0f,12.0f,12.0f);
        weatherData.setData(15.0f,12.0f,12.0f);

    }
}