同步代码块synchronized解决数据安全问题-锁对象是类型.class

package Thread.Thread05;

/**
 * FileName: SellTicketDemo
 * Author:   lps
 * Date:     2022/3/30 15:48
 * Sign:刘品水 Q：1944900433
 */
public class SellTicketDemo {
    public static void main(String[] args) {
        SellTicket st = new SellTicket();
        new Thread(st, "一号").start();
        new Thread(st, "二号").start();
        new Thread(st, "三号").start();


    }
}

package Thread.Thread05;

/**
 * FileName: SellTicket
 * Author:   lps
 * Date:     2022/3/30 15:48
 * Sign:刘品水 Q：1944900433
 */
public class SellTicket implements Runnable {
    //private int ticketnumbers = 100;
    private static int ticketnumbers = 100;
    private Object obj = new Object();
    int x = 0;

    @Override
    public void run() {
        while (true) {
            if (x % 2 == 0) {
//                synchronized (this){
                synchronized (SellTicket.class){
                    //类名.class 得到该类的字节码对象
                    if (ticketnumbers > 0) {
                        try {
                            Thread.sleep(100);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        System.out.println(Thread.currentThread().getName() + "正在销售" + ticketnumbers-- + "张票");

                    }
                }

            } else {
                sendTicket();
            }
            x++;
        }/*{
            if (x % 2 == 0) {
                synchronized (obj) {
                    if (ticketnumbers > 0) {
                        try {
                            Thread.sleep(100);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        System.out.println(Thread.currentThread().getName() + "正在销售" + ticketnumbers-- + "张票");
                    }
                }
            } else {
                synchronized (obj) {
                    if (ticketnumbers > 0) {
                        try {
                            Thread.sleep(100);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        System.out.println(Thread.currentThread().getName() + "正在销售" + ticketnumbers-- + "张票");
                    }
                }

            }

            x++;
            //sendTicket();

        }*/

    }

//    private synchronized void sendTicket() {
//        if (ticketnumbers > 0) {
//            try {
//                Thread.sleep(100);
//            } catch (InterruptedException e) {
//                e.printStackTrace();
//            }
//            System.out.println(Thread.currentThread().getName() + "正在销售" + ticketnumbers-- + "张票");
//
//        }
//    }
private static synchronized void sendTicket() {
    if (ticketnumbers > 0) {
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(Thread.currentThread().getName() + "正在销售" + ticketnumbers-- + "张票");

    }
}
}