在synchronize括号里加this就正常，若是obj就出异常，为什么

Question

public class TicketRunnableDemo implements Runnable {
private int ticketCount = 100;
Object obj = new Object();
@Override
public void run() {
while (true) {
synchronized (obj) {
notify();
if (ticketCount > 0) {
System.out.println(Thread.currentThread().getName() + "座位号：" + ticketCount--);
} else {
break;
}
try {
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}

public class Run {
public static void main(String[] args) {
TicketRunnableDemo ticketRunnableDemo = new TicketRunnableDemo();
new Thread(ticketRunnableDemo,"窗口1").start();;
new Thread(ticketRunnableDemo,"窗口2").start();;
new Thread(ticketRunnableDemo,"窗口3").start();;
new Thread(ticketRunnableDemo,"窗口4").start();;
}
}

Answer 1

https://zhidao.baidu.com/question/276303405.html