利用字段更新器，可以针对对象的某个域（Field）进行原子操作，只能配合 volatile 修饰的字段使用，否则会出现
    异常

    1. Exception in thread "main" java.lang.IllegalArgumentException: Must be volatile type
    1. public class Test40 {
    3.     public static void main(String[] args) {
    4.         Student stu = new Student();
    6.         AtomicReferenceFieldUpdater updater =
    7.                 AtomicReferenceFieldUpdater.newUpdater(Student.class, String.class, "name");
    9.         System.out.println(updater.compareAndSet(stu, null, "张三"));
    10.         System.out.println(stu);
    11.     }
    12. }
    14. class Student {
    15.     volatile String name;
    17.     @Override
    18.     public String toString() {
    19.         return "Student{" +
    20.                 "name='" + name + '\'' +
    21.                 '}';
    22.     }
    23. }

    true Student{name='张三'}