为啥只是加了个打印（注释那个），窗口二卖票了

Question

import java.util.concurrent.locks.ReentrantLock;

public class SellTickets {

    public static void main(String[] args) {
        TicketsWindow tw1 = new TicketsWindow();
        Thread t1 = new Thread(tw1, "一号窗口");
        Thread t2 = new Thread(tw1, "二号窗口");
        t1.start();
        t2.start();
    }
}

class TicketsWindow implements Runnable {
    private int tickets = 10;
    private final ReentrantLock lock = new ReentrantLock();

    @Override
    public void run() {
        while (true) {
        
            //System.out.println(Thread.currentThread().getName());
            
            lock.lock();
            try {
                if (tickets > 0) {
                    System.out.println(Thread.currentThread().getName() 
                                       + "还剩余票:" + tickets + "张");
                    --tickets;
                    System.out.println(Thread.currentThread().getName() 
                                       + "卖出一张火车票,还剩" + tickets + "张");
                } else {
                    System.out.println(Thread.currentThread().getName() 
                                       + "余票不足,暂停出售!");
                    try {
                        Thread.sleep(1000 * 6);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                }
            } finally {
                lock.unlock();
            }
        }
    }
}