设计模式-观察者模式（二）

import java.util.ArrayList;
import java.util.List;

public class ConcreteSubject implements Subject {
    private List<Observer> observers;
    private float temperature;
    private float humidity;
    private float pressure;

    public ConcreteSubject() {
        observers = new ArrayList<>();
    }

    @Override
    public void registerObserver(Observer observer) {
        observers.add(observer);
    }

    @Override
    public void removeObserver(Observer observer) {
        observers.remove(observer);
    }

    @Override
    public void notifyObservers() {
        for (Observer observer : observers) {
            observer.update(temperature, humidity, pressure);
        }
    }

    public void setMeasurements(float temperature, float humidity, float pressure) {
        this.temperature = temperature;
        this.humidity = humidity;
        this.pressure = pressure;
        measurementsChanged();
    }

    public void measurementsChanged() {
        notifyObservers();
    }
}

public class ConcreteObserver implements Observer {
    private float temperature;
    private float humidity;
    private float pressure;

    @Override
    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("Current conditions: " + temperature
                + "F degrees and " + humidity + "% humidity and " + pressure + "Pa");
    }
}