java多线程同步的问题

Question

小测试，如何实现变量ticket的同步

private int ticket = 100;
public void run()
{
    while(ticket > 0 ) {
        System.out.println(ticket+" is saled by "+
                            Thread.currentThread().getName());
        ticket--;
        try
        {
            Thread.sleep(200);
        }
        catch (InterruptedException e)
        {
            e.printStackTrace();
        }
    }
}

Answer 1

这样写public synchronized void run()
{
while(ticket > 0 ) {
System.out.println(ticket+" is saled by "+
Thread.currentThread().getName());
ticket--;
try
{
Thread.sleep(200);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
}

或者这样写

private Object obj = new Object();

public void run() {
    synchronized (obj) {
        while (ticket > 0) {
            System.out.println(ticket + " is saled by "
                    + Thread.currentThread().getName());
            ticket--;
        }
    }
    try {
        Thread.sleep(200);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}