在Java中简单的使用观察者模式

╰半夏微凉° 2022-07-13 09:26 147阅读 0赞

主题接口：

public interface Subject {
        public void registerObserver(observer o);
        public void removeObserver(observer o);
        public void notifyObservers();
    }

观察者接口：

public interface observer {
        public void update(float temp,float humidity,float pressure);
    }

展示接口：

public interface DisplayElement {
        public void display();
    }

主题实现类：

public class WeatherData implements Subject {
        private ArrayList<observer> Observers;
        private float temp,humidity,pressure;
        public WeatherData(){
            Observers = new ArrayList<>();
        }
        @Override
        public void registerObserver(observer o) {
               Observers.add(o);
        }
    
        @Override
        public void removeObserver(observer o) {
            int i = Observers.indexOf(o);
            if (i >= 0){
                Observers.remove(i);
            }
    
        }
    
        @Override
        public void notifyObservers() {
            for (int i = 0; i < Observers.size(); i++) {
                observer o = Observers.get(i);
                o.update(temp,humidity,pressure);
            }
        }
    
        public void measurementsChanged(){
            notifyObservers();
        }
    
        public void setMeasurements(float temp,float humidity,float pressure){
            this.temp = temp;
            this.humidity = humidity;
            this.pressure = pressure;
            measurementsChanged();
        }
    }

观察者实现类：

public class CurrentConditionsDisplay implements observer,DisplayElement {
        private float temp,humidity,pressure;
        public CurrentConditionsDisplay(){
    
        }
        @Override
        public void update(float temp, float humidity, float pressure) {
                this.temp = temp;
                this.humidity = humidity;
                this.pressure = pressure;
                display();
        }
    
        @Override
        public void display() {
            System.out.println("当前天气："+temp+"℃ "+humidity+"湿度 "+pressure+"气压");
        }
    }

主方法类：

public class WeatherStation {
        public static void main(String[] agrs){
            WeatherData data = new WeatherData();
            CurrentConditionsDisplay display = new CurrentConditionsDisplay();
            data.registerObserver(display);
            data.setMeasurements(25,23,56);
        }
    }