关于设计模式:设计模式观察者模式

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

//观察者行为public interface Displayment {    public void display();}

//主题public interface Subject {    public void registerObserver(Observer o);    public void removeObserver(Observer o);    public void notifyObserver();}

//观察者1public class CurrentConditionsDisplay implements Observer, Displayment{    private float temp;    private float humidity;    private Subject weatherData;    public void CurrentConditionsDisplay(Subject weatherData){        this.weatherData = weatherData;    }    public void display() {        System.out.println("Current conditions: " + temp + "F degrees and "+ humidity + " % humidity");    }    public void update(float temp, float humidity, float pressure) {        this.temp = temp;        this.humidity = humidity;        display();    }}

//主题相干的实例public class WeatherData implements Subject {    private ArrayList observers;    private float temperature;    private float humidity;    private float pressure;    public WeatherData(){        this.observers = new ArrayList<Observer>();    }    @Override    public void registerObserver(Observer o) {        observers.add(o);    }    @Override    public void removeObserver(Observer o) {        observers.remove(o);    }    @Override    public void notifyObserver() {        for(int i = 0; i < observers.size(); i++ ){            Observer observer = (Observer) observers.get(i);            observer.update(temperature,humidity,pressure);        }    }    public void measurementsChanged(){        notifyObserver();    }    public void setMeasurements(float temperature, float humidity, float pressure){        this.temperature = temperature;        this.humidity = humidity;        this.pressure = pressure;    }}

//测试public class WeatherDataTest extends TestCase {    public void testRegisterObserver() {        WeatherData weatherData = new WeatherData();        weatherData.setMeasurements(23,15,175);        CurrentConditionsDisplay currentConditionsDisplay = new CurrentConditionsDisplay();//        CurrentConditionsDisplay currentConditionsDisplay = new CurrentConditionsDisplay(weatherData);        weatherData.registerObserver(currentConditionsDisplay);        weatherData.notifyObserver();        weatherData.removeObserver(currentConditionsDisplay);        weatherData.notifyObserver();    }}

//测试后果
Current conditions: 23.0F degrees and 15.0 % humidity