戏说模式之：观察者模式（三体）

/**
 * 主题，每个观察者的管理接口
 */
public interface ISubject {
    public void addObserver(IObserver observer);
    public void deleteObserver(IObserver observer);
    public void notifyObserver(Earth earth);
}

/**
 * 主题的具体实现类
 */
public class ConcreteSubject implements ISubject {
    List<IObserver> observers ;

    public ConcreteSubject(){
        this.observers = new ArrayList<IObserver>();
    }
    @Override
    public void addObserver(IObserver observer) {
        this.observers.add(observer);
    }

    @Override
    public void deleteObserver(IObserver observer) {
        this.observers.remove(observer);
    }

    @Override
    public void notifyObserver(Earth earth) {
        for(IObserver observer : observers){
            observer.update(earth);
        }
    }

    public void timeUp(Earth earth){
        this.notifyObserver(earth);
    }
}

/**
 * 观察者接口，只有一个update方法
 */
public interface IObserver {
    public void update(Earth earth);
}

/**
 * 地球实体bean
 */
public class Earth {
    //武器
    private String weapon;
    //人口
    private long population;
    //技术
    private String technology;
    //水含量
    private float water;
    //温度
    private float temperature;
    //陆地
    private float land;

    public String getWeapon() {
        return weapon;
    }

    public void setWeapon(String weapon) {
        this.weapon = weapon;
    }

    public long getPopulation() {
        return population;
    }

    public void setPopulation(long population) {
        this.population = population;
    }

    public String getTechnology() {
        return technology;
    }

    public void setTechnology(String technology) {
        this.technology = technology;
    }

    public float getWater() {
        return water;
    }

    public void setWater(float water) {
        this.water = water;
    }

    public float getTemperature() {
        return temperature;
    }

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

    public float getLand() {
        return land;
    }

    public void setLand(float land) {
        this.land = land;
    }
}

/**
 * 三体星球观察者
 */
public class ThreeBodyPlanet implements IObserver {
    @Override
    public void update(Earth earth) {
        System.out.println("======三体星球观察者====");
        StringBuffer buf = new StringBuffer();
        buf.append("水资源:"+earth.getWater()+"亿立方千米，");
        buf.append("温度:"+earth.getTemperature() + "℃，");
        buf.append("陆地:"+earth.getLand() + "亿平方公里，");
        buf.append("人口:"+earth.getPopulation() + "亿");
        System.out.println(buf.toString());
    }
}

/**
 * 三体舰队观察者
 */
public class ThreeBodyFleet implements IObserver{
    @Override
    public void update(Earth earth) {
        System.out.println("======三体舰队观察者====");
        StringBuffer buf = new StringBuffer();
        buf.append("武器:"+earth.getWeapon()+"，");
        buf.append("科技:"+earth.getTechnology() + "，");
        buf.append("人口:"+earth.getPopulation() + "亿");
        System.out.println(buf.toString());
    }
}

/**
 * 向三体汇报地球情况的质子
 */
public class Proton {
    @Test
    public void report(){
        Earth earth = new Earth();

        earth.setLand(5.11f);
        earth.setPopulation(70);
        earth.setTechnology("能够利用核能，未掌握曲率引擎，无星际旅行能力");
        earth.setTemperature(15.8f);

        earth.setWater(14f);
        earth.setWeapon("最高级的攻击是核裂变");

        ConcreteSubject concreteSubject = new ConcreteSubject();
        //三体舰队
        ThreeBodyFleet threeBodyFleet = new ThreeBodyFleet();
        //三体星
        ThreeBodyPlanet threeBodyPlanet = new ThreeBodyPlanet();
        //添加具体的观察者（三体舰队）
        concreteSubject.addObserver(threeBodyFleet);
        //添加具体的观察者（三体星）
        concreteSubject.addObserver(threeBodyPlanet);

        //调用通知（时间到了通知）
        concreteSubject.timeUp(earth);

        //因为人类新掌握了核聚变，紧急通知三体舰队（三体星不通知）
        earth.setWeapon("掌握了核聚变");
        concreteSubject.deleteObserver(threeBodyPlanet);
        concreteSubject.timeUp(earth);
    }
}