设计模式之观察者模式

最新推荐文章于 2024-11-02 14:41:55 发布

虔诚的学习者

最新推荐文章于 2024-11-02 14:41:55 发布

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本文链接：https://blog.youkuaiyun.com/qq_38082979/article/details/103697193

本文介绍了一种常用的设计模式——观察者模式，并通过具体的代码实现展示了如何在Java中使用该模式。观察者模式允许一个主题对象管理多个观察者对象，当主题状态发生改变时，所有依赖于它的观察者都会得到通知并自动更新。

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/**
 * @Author: king
 * @Date: 2019/12/24 21:20
 * @Version 1.0
 * 抽象主题
 */
public interface Subject {
    public void addObserver(Observer observer);

    public void deleteObserver(Observer observer);

    public void nofityObservers();
}

/**
 * @Author: king
 * @Date: 2019/12/24 21:21
 * @Version 1.0
 * 抽象观察者
 */
public interface Observer {
    public void hearTel(String msg);
}

import java.util.ArrayList;

/**
 * @Author: king
 * @Date: 2019/12/25 9:32
 * @Version 1.0
 * 具体主题
 */
public class SeekJobCenter implements Subject {
    String msg;
    boolean changed;
    ArrayList<Observer> personList;

    SeekJobCenter() {
        personList = new ArrayList<Observer>();
        msg = "";
        changed = false;
    }

    public void addObserver(Observer observer) {
        if (!personList.contains(observer)) {
            personList.add(observer);
        }
    }

    public void deleteObserver(Observer observer) {
        if (personList.contains(observer)) {
            personList.remove(observer);
        }
    }

    public void nofityObservers() {
        if (changed) {
            for (int i = 0; i < personList.size(); i++) {
                Observer observer = personList.get(i);
                observer.hearTel(msg);
            }
        }
        changed = false;
    }

    public void giveMsg(String str) {
        if (str.equals(msg)) {
            changed = false;
        } else {
            msg = str;
            changed = true;
        }
    }
}

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;

/**
 * @Author: king
 * @Date: 2019/12/25 9:53
 * @Version 1.0
 * 具体观察者-学生
 */
public class Student implements Observer {
    Subject subject;
    File file;

    Student(Subject subject, String filename) {
        this.subject = subject;
        subject.addObserver(this);
        file = new File(filename);
    }

    public void hearTel(String msg) {
        try {
            RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw");
            randomAccessFile.seek(randomAccessFile.length());//设置文件指针位置
            byte[] bytes = msg.getBytes();
            randomAccessFile.write(bytes);
            System.out.print("我是学生，");
            System.out.println("我向文件" + file.getName() + "写入:");
            System.out.println(msg);
        } catch (FileNotFoundException e) {
            System.out.println("文件未找到");
        } catch (IOException e) {
            System.out.println("IO异常");
        }
    }
}

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;

/**
 * @Author: king
 * @Date: 2019/12/25 10:32
 * @Version 1.0
 * 具体观察者-员工
 */
public class Custom implements Observer {
    Subject subject;
    File file;

    Custom(Subject subject, String filename) {
        this.subject = subject;
        subject.addObserver(this);
        file = new File(filename);
    }

    public void hearTel(String msg) {
        try {
            boolean b = msg.contains("java程序员") || msg.contains("软件工程师");
            if (b) {
                RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw");
                randomAccessFile.seek(randomAccessFile.length());//设置文件指针位置
                byte[] bytes = msg.getBytes();
                randomAccessFile.write(bytes);
                System.out.print("我是员工，");
                System.out.println("我向文件" + file.getName() + "写入:");
                System.out.println(msg);
            } else {
                System.out.println("没有有用的信息");
            }
        } catch (FileNotFoundException e) {
            System.out.println("文件未找到");
        } catch (IOException e) {
            System.out.println("IO异常");
        }
    }
}