Myujth

I run the main method after a while, it will always print nothing.

But if I uncomment "System.out.println(111);" and "System.out.println(222);",it will run normal i think.

I fetch the dump of 'soldWorker' thread and 'refundWorker' thread, they stop at the if judge.

public class ProducerAndConsumer2 

 public static void main(String args) 
 SyncTikcet2 syncTikcet = new SyncTikcet2(1);

 Runnable syncSoldTicket = () -> syncTikcet.soldTicket();
 Runnable syncRefundTicket = () -> syncTikcet.refund();

 new Thread(syncSoldTicket, "soldWorker").start();
 new Thread(syncRefundTicket, "refundWorker").start();
 
 

class SyncTikcet2 

 private Integer ticketNum;

 public SyncTikcet2(Integer ticketNum) 
 this.ticketNum = ticketNum;
 


 public void soldTicket() 
 while (true) 
 if (ticketNum > 0) 
 ticketNum = ticketNum - 1;
 System.out.println("sold ticket,the num is" + ticketNum);
 else 
 // System.out.println(111);
 
 
 

 public void refund() 
 while (true) 
 if (ticketNum == 0) 
 ticketNum = ticketNum + 1;
 System.out.println("refund ticket,the num is" + ticketNum);
 else 
 // System.out.println(222);
 
 
 

 public Integer getTicketNum() 
 return ticketNum;
 

 public void setTicketNum(Integer ticketNum) 
 this.ticketNum = ticketNum;
 

If you haven't made the field volatile, there is no reason for a thread to re-read a value it didn't change.

Try using private volatile int ticketNum

I suggest using a primitive e.g. int, unless you have to use an Object reference. It's not only faster but it also makes it clear you don't expect the value to be null.