java多线程快速入门（十七）

多线程通讯实例（必须要有多个线程、必须要管理同一个变量；线程A生产一个变量，线程B消费一个变量）

package com.cppdy;

class User {

    public String username;
    public String sex;
    //如果flag为false    证明变量可写不可读
    //如果flag为true    证明变量可读不可写
    public boolean flag=false;

}

class InputThread extends Thread {
    private User user;

    public InputThread(User user) {
        this.user = user;
    }

    @Override
    public void run() {
        int count = 0;
        while (true) {
            synchronized (user) {
                
                if(user.flag) {
                    try {
                        //这里是等待要去释放锁，线程会一直在这里等待，直到这个变量同一个user调用notify
                        user.wait();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
                
                if (count % 2 == 0) {
                    user.username = "cppdy";
                    user.sex = "nan";
                } else {
                    user.username = "吹泡泡的魚";
                    user.sex = "男";
                }
                count++;
                //将user标记变为可读
                user.flag=true;
                //释放user锁
                user.notify();
            }
        }
    }
}

class OutThread extends Thread {
    private User user;

    public OutThread(User user) {
        this.user = user;
    }

    @Override
    public void run() {
        while (true) {
            synchronized (user) {
                if(!user.flag) {
                    try {
                        user.wait();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
                System.out.println(user.username + "--" + user.sex);
                //将user标记变为可读
                user.flag=false;
                //释放user锁
                user.notify();
            }
        }
    }
}

public class ThreadDemo13 {

    public static void main(String[] args) throws Exception {
        User user = new User();
        InputThread it = new InputThread(user);
        OutThread ot = new OutThread(user);
        it.start();
        ot.start();
    }

}

生产者线程A：如果有值还没读，就等待

消费者线程B：如果全部读完了，就等待