用男友、哥哥、父亲来讲观察者模式

介绍

1、首先需要一个被观察者；
2、被观察者需要具备广播通知的能力；
3、其次需要一批观察者；
4、观察者需要具备观察(接受通知)的能力；

具体见代码

被观察者是一个女孩

public class BeautifulGirl {
    //我的亲人
    private List<Concerner> concerners = new ArrayList<>();
    //我是否生病了
    private boolean isFallIll = false;
    //添加我的亲人
    public void addRelatives(Concerner concerner) {
        this.concerners.add(concerner);
    }
    public boolean isFallIll() {
        return isFallIll;
    }
    //生病了
    public void setFallIll(Boolean isFallIll) {
        this.isFallIll = isFallIll;
        if(isFallIll)
            this.notifyAllRelatives();            
    }
    //告知我的家人
    private void notifyAllRelatives() {
        for (Concerner observer : concerners) {
            observer.care();
        }
    }
}

需要具有亲属关系(观察者必须具备的能力)

public abstract class Concerner {
    protected BeautifulGirl girl;
    @SuppressWarnings("unused")
    private Concerner() {}
    protected Concerner(BeautifulGirl girl) {
        this.girl = girl;
        this.girl.addRelatives(this);
        System.out.println(this.getClass().getName());
    }
    //关心方法
    public abstract void care();
}

各个观察者如下

public class Boyfriend extends Concerner {
    public Boyfriend(BeautifulGirl girl) {
        super(girl);
    }
    @Override
    public void care() {
        boolean fallIll = this.girl.isFallIll();
        if (fallIll)
            System.out.println("亲爱的，我生病了");
        System.out.println("多喝水呀！宝贝~");
        System.out.println("--------------------");
    }
}
public class Brother extends Concerner {
    public Brother(BeautifulGirl girl) {
        super(girl);
    }
    @Override
    public void care() {
        boolean fallIll = this.girl.isFallIll();
        if (fallIll)
            System.out.println("哥哥，我生病了");
        System.out.println("要紧么？赶紧去医院看病呀！我先给你转1000块钱过去呀~");
        System.out.println("--------------------");
    }
}
public class Father extends Concerner {
    public Father(BeautifulGirl girl) {
        super(girl);
    }
    @Override
    public void care() {
        boolean fallIll = this.girl.isFallIll();
        if (fallIll)
            System.out.println("爸爸，我生病了");
        System.out.println("你现在在哪？我马上赶过来！");
        System.out.println("--------------------");
    }
}

如果女孩生病了，测试一下各个亲属的反应

public class ObserverTest {
    public static void main(String[] args) {
        BeautifulGirl girl = new BeautifulGirl();//被大家观察的目标
        new Boyfriend(girl);
        new Brother(girl);
        new Father(girl);
        girl.setFallIll(true);
    }
}

结果可见

image.png