class Ticket extends Thread {
private static int tick =100;
public void run() {
  while (true) {
   if (tick>0) {
    System.out.println(Thread.currentThread().getName()+"...sale..."+tick--);
   }
  }
}
}
class TicketDemo {
public static void main(String[] args) {
  Ticket t1 = new Ticket();
  Ticket t2 = new Ticket();
  Ticket t3 = new Ticket();
  Ticket t4 = new Ticket();
  t1.start();
  t2.start();
  t3.start();
  t4.start();

}
}

这个要用synchronized 关键字控制资源共享。

应该加线程同步的,要不然就会出现这种情况