简单实现的观察者模式

代码的主要功能是实现天气预报。

package cn.exercise.algorithmsTest;

import java.util.ArrayList;

public class Observable {
    // 被观察者接口
    interface Subject {
        public void registerObserver(Observer o);

        public void removeObserver(Observer o);

        public void notifyObservers();;
    }

    //被观察者的具体实现
    static class Whether implements Subject {
        private ArrayList observers = new ArrayList();
        private float temperature;

        public void registerObserver(Observer o) {
            this.observers.add(o);
        }

        public void removeObserver(Observer o) {
            this.observers.remove(o);
        }

        public void notifyObservers() {
            for (int i = 0; i < observers.size(); i++) {
                this.observers.get(i).update(temperature);
            }
        }

        public float getTemperature() {
            return temperature;
        }

        public void setTemperature(float temperature) {
            this.temperature = temperature;
            notifyObservers();
        }

    }

    //观察者
    interface Observer {
        // 更新温度
        public void update(float temp);
    }

    //观察者的具体实现1
    static class WhetherDisplay1 implements Observer {
        private float temprature;

        private WhetherDisplay1(Subject whether) {
            whether.registerObserver(this);
        }

        public void update(float temp) {
            this.temprature = temp;
            display();
        }

        public void display() {
            System.out.println("display1****:" + this.temprature);
        }

    }

    //观察者的具体实现2
    static class WhetherDisplay2 implements Observer {
        private float temprature;

        private WhetherDisplay2(Subject whether) {
            whether.registerObserver(this);
        }

        public void update(float temp) {
            this.temprature = temp;
            display();
        }

        public void display() {
            System.out.println("display2****:" + this.temprature);
        }

    }

    public static void main(String[] args) {
        Whether whether = new Whether();
        WhetherDisplay1 d1 = new WhetherDisplay1(whether);
        WhetherDisplay2 d2 = new WhetherDisplay2(whether);
        //当被观察者改变温度，观察者会做出相应的动作
        whether.setTemperature(27);
        whether.setTemperature(26);
    }
}