Java线程卖票问题

关于线程安全的演示代码

public class MyRunnable implements Runnable{
    int i = 100;
    @Override
    public void run() {
        while (true){
            if (i<1){
                System.out.println("票卖完了");
                break;
            }
            try {
                Thread.currentThread().sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+":正在出售第"+i+"张票");
            --i;
        }
    }
}

public class ThreadTest {
    public static void main(String[] args) {
        MyRunnable my = new MyRunnable();
        Thread thread1 = new Thread(my, "窗口1");
        Thread thread2 = new Thread(my, "窗口2");
        Thread thread3 = new Thread(my, "窗口3");
        Thread thread4 = new Thread(my, "窗口4");
        thread1.start();
        thread2.start();
        thread3.start();
        thread4.start();
    }
}

出现卖重复票，漏票，负数票问题。

使用synchronized关键字解决问题

public class MyRunnable implements Runnable{
    int i = 100;
    @Override
    public void run() {
        while (true){
            //票卖完结束
            if (sellTickets())break;
        }
    }
    //同步方法
    public synchronized boolean sellTickets(){
        if (i<1){
            System.out.println("票卖完了");
            return true;
        }
        try {
            Thread.currentThread().sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(Thread.currentThread().getName()+":正在出售第"+i+"张票");
        --i;
        return false;
    }
}

使用Lock锁

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

public class MyRunnable implements Runnable{
    int i = 100;
    Lock lock = new ReentrantLock();
    @Override
    public void run() {
        while (true){
            lock.lock();
            //票卖完结束
            if (i<1){
                System.out.println("票卖完了");
                break;
            }
            try {
                Thread.currentThread().sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+":正在出售第"+i+"张票");
            --i;
            try{

            }finally {
                 lock.unlock();
            }
        }
    }