AtomicReferenceFieldUpdater的使用问题

class DemoData{
public volatile int value1 = 1;
volatile int value2 = 2;
protected volatile int value3 = 3;
private volatile int value4 = 4;
volatile Integer value5=5;
}
final AtomicReferenceFieldUpdater updater=AtomicReferenceFieldUpdater.newUpdater(DemoData.class, Integer.class, "value5"); //

for(int i = 0 ; i < 10 ; i++) { //开启10个线程

            new Thread() {
                public void run() {
                    try {
                       Thread.sleep(1000);
                   } catch (InterruptedException e) {
                       e.printStackTrace();
                   }
                   updater.compareAndSet(data, data.value5, data.value5+1);
                   //int now = data.value5;
                   //System.out.println(Thread.currentThread().getName() + " get value : " + now);
                }
            }.start();
        }
        Thread.sleep(2000);
        System.out.println("最后的值:"+data.value5);

        不是原子的么，最后的结果和没用一样，求大神科普

http://huangyunbin.iteye.com/blog/1944153