設計模式--觀察者模式

類圖

源碼

Observer.java
package com.demo;

public interface Observer {

    public void moneyUp();
    public void moneyDown();
}


Subject.java
package com.demo;

import java.util.ArrayList;

public abstract class Subject {
    protected ArrayList<Observer> olist=new ArrayList<>();
    public Subject() {
        // TODO Auto-generated constructor stub
    }
    public void add(Observer o) {
        olist.add(o);
    }
    public void remove(Observer o) {
        olist.remove(o);
    }
    public abstract void up(double a);
    public abstract void down(double a);

}

GuMin.java
package com.demo;

public class GuMin implements Observer{
     
    private String name;
    public GuMin(String n) {
        // TODO Auto-generated constructor stub
        name=n;
    }

    @Override
    public void moneyUp() {
        // TODO Auto-generated method stub
          System.out.println(name+"買了一些股票（股票升了）");
    }

    @Override
    public void moneyDown() {
        // TODO Auto-generated method stub
        System.out.println(name+"股票降價了，哭了");
    }

}

GuPiao.java
package com.demo;

public class GuPiao extends Subject{

    public GuPiao() {
        // TODO Auto-generated constructor stub
    }

    /*
     * public void add(Observer o) { super.add(o); }
     */
    public void up(double a) {
        // TODO Auto-generated method stub
        if(a>0.05)
        for(Observer gum : olist){
                gum.moneyUp();;
        }
    }

    public void down(double a) {
        // TODO Auto-generated method stub
        if(a>0.05)
            for(Observer gum:olist){
                    gum.moneyDown();;
            }
    }

}

Client.java
package com.demo;

public class Client {

    public static void main(String[]args) {
        // TODO Auto-generated constructor stub
            Subject f=new GuPiao();
            GuMin g1=new GuMin("股民A");
            GuMin g2=new GuMin("股民B");
            f.add(g1);
            f.add(g2);
            System.out.println("股票升了");
            f.up(0.1);
            System.out.println("比率小于0.05");
            System.out.println();
            f.down(0.001);
            
            System.out.println("股票降了");
            f.down(0.1);
            System.out.println("比率小于0.05");
            f.down(0.001);
    }

}      

測試截圖