volatile 可见性的测试

 1 public class VolatileTest {
 2 
 3     private static boolean flag = true; //不用volatile修饰
 4 
 5     public static void main(String[] args) throws InterruptedException {
 6         new Thread1().start();
 7         Thread.sleep(1000); //暂停1秒 保证线程1 启动并运行。
 8         new Thread2().start();
 9     }
10 
11     /**
12      * 线程1 一个循环，如果 flag为false 跳出循环
13      */
14     static class Thread1 extends Thread {
15         @Override
16         public void run() {
17             while (flag) {
18 
19             }
20             System.out.println("thread1-run");
21         }
22     }
23 
24     /**
25      * 线程2  2秒后将flag改成false
26      */
27     static class Thread2 extends Thread {
28         @Override
29         public void run() {
30             try {
31                 Thread.sleep(2000);
32             } catch (InterruptedException e) {
33                 e.printStackTrace();
34             }
35             System.out.println("Thread2-run");
36             flag = false;
37             System.out.println("flag 被改成false");
38         }
39     }
40 }

private static volatile boolean flag = true;