多线程（1_锁的认识_2_死锁分析）

我们创建4个线程，与之前不同的是，同时使用了同步函数和同步代码快。看看结果如何

class Mlpc implements Runnable
{
    private int ticket = 550;
    public boolean flag = true;
    Object obj = new Object();
    public void run()
    {
        if(flag == true)
        {
            while(true)
            {
                synchronized (obj)
                {
                    if(ticket>0)
                    {
                        if(ticket>0)
                        {
                            try
                            {
                                Thread.sleep(20);
                            }
                            catch (Exception e)
                            {
                            }
                            System.out.println(Thread.currentThread()+" show "+ticket--);
                        }
                    }
                }
            }
        }
        else
        {
            while(true)
            {
                show();
            }
        }

    }
    public synchronized void show()
    {

            if(ticket>0)
            {
                try
                {
                    Thread.sleep(20);
                }
                catch (Exception e)
                {
                }
                System.out.println(Thread.currentThread()+" show "+ticket--);
            } 

    }
}

 class mlpcDemo
{
    public static void main(String[] args)
    {

        Mlpc m = new Mlpc();
        Thread th0 = new Thread(m);
        Thread th1 = new Thread(m);
        Thread th2 = new Thread(m);
        Thread th3 = new Thread(m);

        th0.start();
        try
        {
            Thread.sleep(20);
        }
        catch (Exception e)
        {
        }
        m.flag = false;
        th1.start();
        th2.start();
        th3.start();
    }
}

结果出现了票数为0。

 public void run()
    {
        if(flag == true)
        {
            while(true)
            {
               synchronized (this) //从原本的任意对象改为函数自己所属的对象this               {
                    if(ticket>0)
                    {
                        try
                        {
                            Thread.sleep(20);
                        }
                        catch (Exception e)
                        {
                        }
                        System.out.println(Thread.currentThread()+" show "+ticket--);
                    }
                }
            }
        }
        else
        {
            while(true)
            {
                show();
            }
        }

    }