volatitle 不具有原子性代码

public class TestVolatitle_1 {
    public  volatile static   int  j;
    public int  add (){

        synchronized (TestVolatitle_1.class){
            return j++;
        }
    }

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

        TestVolatitle_1 testVolatitle_1 = new TestVolatitle_1();
        for (int i = 0; i < 100; i++) {
            new Thread(){
                @Override
                public void  run() {
                   // testVolatitle_1.add();
                    /*synchronized (TestVolatitle_1.class){
                        j++;
                    }*/
                    for (int k = 0; k < 2000; k++) {
                        j++ ;
                    }


                }
            }.start();
        }
        Thread.sleep(3000);
       // System.out.println(testVolatitle_1.j);
        System.out.println(j);
    }

}

最终输出结果   197238

执行的程序加上代码块 执行正常

  synchronized (TestVolatitle_1.class){
                        for (int k = 0; k < 2000; k++) {
                            j++ ;
                        }
                    }