來源：AtomicReference與volatile的區別

AtomicReference與volatile的在可見性上的意義是一致的。

volatile不能保證原子性，AutomicReference實現上則用了volatile和Unsafe.compareAndSwapObject()來分別保證可見性和原子性。

 1 package org.liws;
 2 
 3 import java.util.concurrent.atomic.AtomicReference;
 4 import org.junit.Test;
 5 
 6 public class
 
 Snippet {
 7     
 8     private static volatile Integer volatileInt = 0;
 9     private static AtomicReference<Integer> atmicRef = new AtomicReference<Integer>(volatileInt);
10     
11     /** 驗證volatile不能保證原子性 */
12     @Test public void test_volatile() throws InterruptedException {
 
13         for (int i = 0; i < 100; i++) {
14             new Thread(new Runnable() {
15                 @Override public void run() {
16                     for (int i = 0; i < 10000; i++) {
17                         volatileInt++;
18                     }
19                 }
20             }).start();
 
21         }
22         Thread.sleep(1000);
23         System.out.println(volatileInt); // something like 398793
24     }
25 
26     /** 驗證test_AtomicReference能保證原子性 */
27     @Test public void test_AtomicReference() throws InterruptedException{
28         for (int i = 0; i < 100; i++) {
29             new Thread(new Runnable(){
30                 @Override public void run() {
31                     for (int i = 0; i < 10000; i++) {
32                         while (true) {
33                             Integer temp = atmicRef.get();
34                             if (atmicRef.compareAndSet(temp, temp + 1)) {
35                                 break;
36                             }
37                         }
38                     }
39                 }       
40             }).start();
41         }
42         Thread.sleep(1000);
43         System.out.println(atmicRef.get()); //1000000
44     }
45 }

【轉】AtomicReference與volatile的區別