在靜態方法上面加synchonizd用的是位元組碼檔案鎖

package com.cppdy;

class MyThread8 implements Runnable {

    private static Integer ticketCount = 100;
    public boolean falg = true;

    @Override
    public void run() {
        if (falg) {
            synchronized (MyThread8.class) {
                while (ticketCount > 0) {
                    
 
try {
                        Thread.sleep(50);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName() + "賣出了第：" + (100 - ticketCount + 1) + "張票。");
                    ticketCount
 
--;
                }
            }
        } else {
            while (ticketCount > 0) {
                sale();
            }
        }
    }

    public static synchronized void sale() {
        if (ticketCount > 0) {
            try {
                Thread.sleep(50);
            } catch (Exception e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() 
 
+ "賣出了第：" + (100 - ticketCount + 1) + "張票。");
            ticketCount--;
        }
    }
}

public class ThreadDemo8 {

    public static void main(String[] args) throws Exception {
        MyThread8 mt = new MyThread8();
        Thread thread1 = new Thread(mt, "視窗1");
        Thread thread2 = new Thread(mt, "視窗2");
        thread1.start();
        Thread.sleep(30);
        mt.falg = false;
        thread2.start();
    }

}

一般情況下，不使用static鎖：JVM編譯的時候，static是存到方法區，方法區是垃圾回收機制不會回收的