多线程安全问题之Lock显示锁

Posted 2021-01-23 huangleshu

package com.hls.juc;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * 解决多线程安全问题的方式: 3种
 * synchronized: 隐式锁
 * 1. 同步方法
 * 2. 同步代码块
 *
 * 3.Lock同步锁: 显示锁  可以更加灵活的控制同步的代码访问
 * 注意 : 必须 显示上锁 lock()  必须在finally块中释放锁unlock()
 *
 */

public class LockTask {
    public static void main(String[] args) {
        TicketTask ticketTask = new TicketTask();
        new Thread(ticketTask, "1号窗口").start();
        new Thread(ticketTask, "2号窗口").start();
        new Thread(ticketTask, "3号窗口").start();

    }
}

class TicketTask implements Runnable{
    private int ticket = 10;
    private Lock lock = new ReentrantLock();
    @Override
    public void run() {
        while (true){
            lock.lock();
            try {
                if(ticket > 0){
                    try {
                        Thread.sleep(100);
                        System.out.println(Thread.currentThread().getName() + "已售票, 余票" + --ticket);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }else {
                    break;
                }
            } finally {
                //务必在finally块中释放锁
                lock.unlock();
            }
        }
    }
}