观察者模式

public class cartoon {
    private Vector<student> studentlist=new Vector();  //定义学生数组
    private String active;     //定义活动
    
    public String getActive() {       //获取活动
        return active;
    }

    public void setActive(String active) {  //设置活动
        this.active = active;
    }
    
    public void add(student student) {
        studentlist.add(student);        //增添学生
    }
    
    public void update(){
        for(student s:studentlist){
            s.respond();
        }
    }
}

public class student {
    private String name;
    private cartoon cartoon;
    public student(String name,cartoon cartoon) {
        this.cartoon=cartoon;
        this.name=name;
    }
    public void respond() {
        System.out.println(cartoon.getActive()+","+name+" 请去观看哦");
    }
}

public class client {
    public static void main(String[] args) {
        cartoon 葫芦娃=new cartoon();
        student student1=new student("小明", 葫芦娃);
        student student2=new student("小红", 葫芦娃);
        葫芦娃.add(student1);
        葫芦娃.add(student2);
        葫芦娃.setActive("葫芦娃更新了");
        葫芦娃.update();
    }
}

import java.util.Vector;

public class biganimal {
    private String active;
    private Vector<animal> animals=new Vector();
    public String getactive() {
        return active;
    }
    public void setactive(String active) {
        this.active = active;
    }
    public void add(animal s) {
        animals.add(s);
    }
    public void change() {
        for(animal a :animals)
        {
            a.respond();
        }
    }
    
}

public class animal {
    String name;
    private biganimal biganimal;
    public animal(String s,biganimal loin)
    {
        this.biganimal=loin;
        this.name=s;
    }
    public void respond() {
        System.out.println(biganimal.getactive()+" "+name+"快跑");
    }
}

public class client {
    public static void main(String[] args) {
        biganimal 老虎=new biganimal();
        animal animal1=new animal("小猴子", 老虎);
        animal animal2=new animal("小猪", 老虎);
        animal animal3=new animal("小鹿", 老虎);
        老虎.add(animal1);
        老虎.add(animal2);
        老虎.add(animal3);
        老虎.setactive("老虎来了");
        老虎.change();
    }
}