为什么main线程(主线程)不能停止while死循环，而子线程（自定义）可以？多线程大神来

/**

 * @author ：jiaolian

 * @date ：Created in 2020-12-21 14:01

 * @description：死循环不能停止线程情况

 * @modified By：

 */

public class CantStopVolatile {



    private static boolean notStop = true;



    public static void main(String[] args) throws InterruptedException {

        PrintString printString = new PrintString();

        printString.printString();

        printString.setNotStop(false);

    }



    private static class PrintString extends Thread {

        //默认不停止打印;

        private boolean notStop = true;



        public boolean isNotStop() {

            return notStop;

        }



        public void setNotStop(boolean notStop) {

            this.notStop = notStop;

        }





        public void printString() {

            while (notStop) {

                try {

                    System.out.println("ThreadName:"+Thread.currentThread().getName());

                    //Thread.sleep(1000);

                } catch (Exception e) {

                    e.printStackTrace();

                }

            }

        }



    }

}