package thread.worker;
/**
* Created by huli3 on 2017/8/16.
*/
public class ExecutorTest {
static int sum = 0;
public static void main(String[] args) throws InterruptedException {
ThreadGroup hl = new ThreadGroup("hl");
for (int i = 0; i < 10; i++) {
Thread thread = new Thread(hl, new MyThread(hl));
thread.start();
}
while (hl.activeCount() > 0) {
Thread.currentThread().yield();
}
System.out.println(sum);
}
static class MyThread implements Runnable {
ThreadGroup threadGroup;
public MyThread(ThreadGroup threadGroup) {
this.threadGroup = threadGroup;
}
public void run() {
for (int j = 0; j < 4; j++) {
sum++;
System.out.println(threadGroup.activeCount() + " sum " + sum + " and current thread is :" + "id:"+Thread.currentThread().getId());
}
// System.out.println(threadGroup.activeCount() + " sum " + sum + " and current thread is :" + Thread.currentThread().getId());
}
}
}

多线程静态变量累加求和 , 计算结果是对的,但是不明白为什么是对的.
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6条回答 默认 最新
- 砸死接触 2017-08-16 13:22关注
因为你用了volatile 修饰变量啊,所以线程里的每次取值都是新的,但是你的System.out.println()打印比较低效,所以会有看起来乱的现象
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