返回信息流class SellTickets implements Runnable {
private Tickets t = new Tickets();
public void run() {
while(t.tickets > 0) {
try{
Thread.sleep(50);
} catch(InterruptedException e) {
e.printStackTrace();
}
t.sell();
}
}
}
class Tickets {
int tickets = 20;
public synchronized void sell() {
System.out.println(Thread.currentThread().getName() + " is selling tickets " + tickets--);
}
}
public class SellTicketsTester {
public static void main(String[] args) {
SellTickets st = new SellTickets();
new Thread(st).start();
new Thread(st).start();
new Thread(st).start();
}
}
循环时判断语句是tickets>0, 为什么会输出0和1呢？
Thread-1 is selling tickets 20
Thread-0 is selling tickets 19
Thread-2 is selling tickets 18
Thread-1 is selling tickets 17
Thread-0 is selling tickets 16
Thread-2 is selling tickets 15
Thread-1 is selling tickets 14
Thread-0 is selling tickets 13
Thread-2 is selling tickets 12
Thread-1 is selling tickets 11
Thread-0 is selling tickets 10
Thread-2 is selling tickets 9
Thread-1 is selling tickets 8
Thread-2 is selling tickets 7
Thread-0 is selling tickets 6
Thread-1 is selling tickets 5
Thread-2 is selling tickets 4
Thread-0 is selling tickets 3
Thread-1 is selling tickets 2
Thread-2 is selling tickets 1
Thread-0 is selling tickets 0
Thread-1 is selling tickets -1
这是一条镜像帖。来源：北邮人论坛 / java / #34958同步于 2014/9/26
该镜像源已超过 30 天没有更新，可能在源站已被删除。
Java机器人发帖
请教一个线程同步问题，麻烦大家帮忙看一下
wei866
2014/9/26镜像同步5 回复
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5 条回复
假设在某一时刻，Tickets.tickets为1
在这一时刻，三个线程同时执行到while(t.tickets>0)那句
于是都能够满足，就都进入到这次循环中，于是 分别输出了1、0、-1
【 在 wei866 (wei866) 的大作中提到: 】
: class SellTickets implements Runnable {
: private Tickets t = new Tickets();
: public void run() {
: ...................
谢谢，就是说在判断之前就应该加锁是吗？
【 在 taoch 的大作中提到: 】
: 假设在某一时刻，Tickets.tickets为1
: 在这一时刻，三个线程同时执行到while(t.tickets>0)那句
: 于是都能够满足，就都进入到这次循环中，于是 分别输出了1、0、-1
: ...................