观察者模式(1)

观察者模式的四种角色：

1、主题接口（Subject）:规定了具体主题需要实现的方法

2、观察者接口（Observer）:规定了用来更新数据的方法

3、具体主题（ConcreteSubject）:实现主题接口

4、具体观察者（ConcreteObserver）:实现了观察者接口

主题接口：

package DesignPatterns.ObserverMode;

public interface Subject {
    void addObserver(Observer observer);
    void deleteObserver(Observer observer);
    void notifyObserver();
}

具体主题：

package DesignPatterns.ObserverMode;

import javax.print.DocFlavor;
import java.util.ArrayList;

public class SeekJobCenter  implements  Subject{
    ArrayList<Observer> arrayList;
    String mess;
    boolean changed;
    public SeekJobCenter()
    {
        arrayList=new ArrayList<Observer>();
        mess="";
        changed=false;
    }
    @Override
    public void addObserver(Observer observer) {
        if (!arrayList.contains(observer))
        {
            arrayList.add(observer);
        }
    }

    @Override
    public void deleteObserver(Observer observer) {
        if (arrayList.contains(observer))
        {
            arrayList.remove(observer);
        }
    }

    @Override
    public void notifyObserver() {
        if (changed)
        {
            for (int i=0;i<arrayList.size();i++)
            {
                Observer observer=arrayList.get(i);
                observer.hearTelephone(mess);
            }
            changed=false;
        }
    }
    public void giveNewMess(String newmMess)
    {
        if (mess.equals(newmMess))
        {
            changed=false;
        }else {
            mess=newmMess;
            changed=true;
        }
    }
}


观察者接口：

package DesignPatterns.ObserverMode;

public interface Observer {
    void hearTelephone(String mess);
}


海归学生观察者：

package DesignPatterns.ObserverMode;

public class HStudent implements Observer {
    Subject subject;
    String messOfQiuZhi;
    public HStudent(String messOfQiuZhi,Subject subject)
    {
        this.subject=subject;
        subject.addObserver(this);
        this.messOfQiuZhi=messOfQiuZhi;
    }
    @Override
    public void hearTelephone(String mess) {
        System.out.println("海归大学生");
        System.out.println("我的求职意向："+messOfQiuZhi);
        System.out.println("市场通知："+mess);
        if (mess.equals(messOfQiuZhi))
        {
            System.out.println("求职意向相符，可以投递");
        }else {
            System.out.println("求职意向不符，不建议投递");
        }
    }
}


国内学生观察者：

package DesignPatterns.ObserverMode;

public class CStudent implements Observer {
    Subject subject;
    String messOfQiuZhi;
    public CStudent(String messOfQiuZhi,Subject subject)
    {
        this.subject=subject;
        subject.addObserver(this);
        this.messOfQiuZhi=messOfQiuZhi;
    }
    public void hearTelephone(String mess) {
        System.out.println("国内大学生");
        System.out.println("我的求职意向："+messOfQiuZhi);
        System.out.println("市场通知："+mess);
        if (mess.equals(messOfQiuZhi))
        {
            System.out.println("求职意向相符，可以投递");
        }else {
            System.out.println("求职意向不符，不建议投递");
        }
    }
}


测试类：

package DesignPatterns.ObserverMode;

public class Application {
    public static void main(String[] args) {
        SeekJobCenter seekJobCenter=new SeekJobCenter();
        CStudent cStudent=new CStudent("java程序员",seekJobCenter);
        HStudent hStudent=new HStudent("产品经理",seekJobCenter);
        seekJobCenter.giveNewMess("java程序员");
        seekJobCenter.notifyObserver();
        seekJobCenter.deleteObserver(cStudent);
        seekJobCenter.giveNewMess("产品经理");
        seekJobCenter.notifyObserver();
    }
}