i++操作非原子的验证代码

Posted 2021-02-16 mozq

 1 package incre;
 2 
 3 public class Incre {
 4     public static void main(String[] args) {
 5         class Count implements Runnable {
 6             public int num;
 7             @Override
 8             public void run() {
 9                 //自增操作，非原子操作，线程不安全
10 //                for (int i = 0; i < 10000; i++) {
11 //                    num++;
12 //                }
13 
14                 //对代码进行同步，查看正确结果。
15                 synchronized (this) {
16                     for (int i = 0; i < 10000; i++) {
17                         num++;
18                     }
19                 }
20             }
21 
22             public int getNum(){
23                 return num;
24             }
25         }
26 
27         Count c = new Count();
28 
29         //创建多个线程
30         final int THREAD_COUNT = 10;
31         Thread[] threadArray = new Thread[THREAD_COUNT];
32         for(int i = 0; i < threadArray.length; i++){
33             threadArray[i] = new Thread(c);
34         }
35 
36         //启动多个线程
37         for(Thread t : threadArray){
38             t.start();
39         }
40 
41         //等待这些线程结束
42         for(Thread t : threadArray){
43             try {
44                 t.join();
45             } catch (InterruptedException e) {
46                 e.printStackTrace();
47             }
48         }
49 
50         //查看计数结果
51         System.out.println("计数结果：" + c.getNum());
52     }
53 }

i++非原子操作验证代码