观察者模式例题代码实现

た入场券 2022-04-23 15:26 167阅读 0赞

题目：小明和小张去中介租房子，小明需求3室两厅的房子，租金不超过6000，小张需求租金不超过1500的房子，中介说你们留下信息，等我有房源通知你们，设计这样的场景并执行输出。

以下是实现代码。如有错误或可优化的地方请提出意见和建议，感谢：

import java.util.ArrayList;
    
    /**
     * @author czh
     */
    public class ObserverTest {
        public static void main(String[] args) {
            IntermediarySubject intermediarySubject = new Intermediary();
    
            Person ming = new Ming();
            Person zhang = new Zhang();
            intermediarySubject.register(ming);
            intermediarySubject.register(zhang);
    
            HouseInfo firstHouseInfo = new HouseInfo();
            firstHouseInfo.setBedRoomNum(3);
            firstHouseInfo.setLivingRoomNum(2);
            firstHouseInfo.setPrice(5000);
            intermediarySubject.sendHouseInfo(firstHouseInfo);
    
            HouseInfo secondHouseInfo = new HouseInfo();
            secondHouseInfo.setBedRoomNum(1);
            secondHouseInfo.setLivingRoomNum(1);
            secondHouseInfo.setPrice(1200);
            intermediarySubject.sendHouseInfo(secondHouseInfo);
        }
    }
    
    /**
     * 抽象的被观察者
     */
    interface IntermediarySubject {
    
        /**
         * 向被观察者注册客户
         *
         * @param person 房屋需求者
         */
        public void register(Person person);
    
        /**
         * 被观察者注销客户
         *
         * @param person 房屋需求者
         */
        public void remove(Person person);
    
        /**
         * 向客户发送房屋信息
         * @param houseInfo 房屋信息
         */
        public void sendHouseInfo(HouseInfo houseInfo);
    }
    
    /**
     * 中介商
     */
    class Intermediary implements IntermediarySubject {
    
        /**
         * 保存需要发送信息人的列表
         */
        private ArrayList<Person> list = new ArrayList<>();
    
        @Override
        public void register(Person person) {
            list.add(person);
        }
    
        @Override
        public void remove(Person person) {
            list.remove(person);
        }
    
        @Override
        public void sendHouseInfo(HouseInfo houseInfo) {
            for (Person person : list) {
                person.setHouseInfo(houseInfo);
            }
        }
    }
    
    /**
     * 房屋信息
     */
    class HouseInfo {
    
        private int livingRoomNum;
        private int bedRoomNum;
        private double price;
    
        public int getLivingRoomNum() {
            return livingRoomNum;
        }
    
        public void setLivingRoomNum(int livingRoomNum) {
            this.livingRoomNum = livingRoomNum;
        }
    
        public int getBedRoomNum() {
            return bedRoomNum;
        }
    
        public void setBedRoomNum(int bedRoomNum) {
            this.bedRoomNum = bedRoomNum;
        }
    
        public double getPrice() {
            return price;
        }
    
        public void setPrice(double price) {
            this.price = price;
        }
    
        @Override
        public String toString() {
            return "livingRoomNum :" + livingRoomNum + " bedRoomNum :" + bedRoomNum + " price:" + price;
        }
    }
    
    /**
     * 抽象的观察者
     */
    class Person {
    
        protected HouseInfo houseInfo;
    
        public void setHouseInfo(HouseInfo houseInfo) {
            this.houseInfo = houseInfo;
            printHouseInfo();
        }
    
        public HouseInfo getHouseInfo(){
            return houseInfo;
        }
    
        public void printHouseInfo() {
            System.out.println(getHouseInfo().toString());
        }
    
    }
    
    class Ming extends Person {
    
        /**
         * 小明需求的房屋价格
         */
        private final int MING_NEED_PRICE = 6000;
    
        /**
         * 小明需求的客厅数量
         */
        private final int MING_NEED_LIVINGROOM_NUM = 2;
    
        /**
         * 小明需求的卧室数量
         */
        private final double MING_NEED_BEDROOM_NUM = 3;
    
        @Override
        public void printHouseInfo() {
            if(checkNeed()){
                System.out.println("Ming want to rent the house," + getHouseInfo().toString());
            }
        }
    
        /**
         * 核验需求
         * @return 满足需求返回true，否则返回false
         */
        public boolean checkNeed(){
            HouseInfo houseInfo = getHouseInfo();
            int bedRoomNum = houseInfo.getBedRoomNum();
            int livingRoomNum = houseInfo.getLivingRoomNum();
            double price = houseInfo.getPrice();
            if(bedRoomNum == MING_NEED_BEDROOM_NUM && livingRoomNum == MING_NEED_LIVINGROOM_NUM && price <= MING_NEED_PRICE){
                return true;
            }else {
                return false;
            }
        }
    
    }
    
    class Zhang extends Person {
    
        /**
         * 小张需求的房屋价格
         */
        private final int ZHANG_NEED_PRICE = 1500;
    
        @Override
        public void printHouseInfo() {
            if(checkNeed()){
                System.out.println("Zhang want to rent the house," + getHouseInfo().toString());
            }
        }
    
        /**
         * 核验需求
         * @return 满足需求返回true，否则返回false
         */
        public boolean checkNeed(){
            HouseInfo houseInfo = getHouseInfo();
            double price = houseInfo.getPrice();
            if(price <= ZHANG_NEED_PRICE){
                return true;
            }else {
                return false;
            }
        }
    
    }

输出如下：

![20190331110733526.png][]

总结：观察者模式完成了观察者和被观察者之间地解耦，可以看作是一种发布订阅模式，不过与之地区别就是观察者和被观察者是直接操作的，可以看成是一种同步地操作，而发布订阅模式发布者和订阅者之间通过中间管理者进行操作的，可以看成是一种异步的操作。

[20190331110733526.png]: /images/20220226/ce66dc0f88ed45398e3e1417f934b932.png