子类集成父类调用父类的synchronized方法，多个线程调用时还是会顺序执行啊，不需要跟老师说的需要在子类中单独声明，为什么？

来源：3-3 线程安全性-原子性-synchronized

imooc_lvshun

2020-04-07

@Slf4j
public class SyncTest {

    public void test1() {
        synchronized (this) {
            for (int i = 0; i < 10; i++) {
                log.info("test1 {}", i);
            }
        }
    }

    public synchronized void test2() {
        for (int i = 0; i < 10; i++) {
            log.info("test2 {}", i);
        }
    }
}

子类代码

@Slf4j
public class SyncTestSub extends SyncTest{

    public static void main(String[] args) {
        SyncTestSub sub = new SyncTestSub();
        ExecutorService executorService = Executors.newCachedThreadPool();
        executorService.execute(() ->
                {
                    sub.test2();
                }
        );
        executorService.execute(() ->
                {
                    sub.test2();
                }
        );

        executorService.execute(() ->
                {
                    sub.test2();
                }
        );
        executorService.shutdown();
    }
}

最终执行日志

00:52:46.175 [pool-1-thread-1] INFO com.lv.demo.concurrency.sync.SyncTest - test2 0
00:52:46.178 [pool-1-thread-1] INFO com.lv.demo.concurrency.sync.SyncTest - test2 1
00:52:46.178 [pool-1-thread-1] INFO com.lv.demo.concurrency.sync.SyncTest - test2 2
00:52:46.178 [pool-1-thread-1] INFO com.lv.demo.concurrency.sync.SyncTest - test2 3
00:52:46.178 [pool-1-thread-1] INFO com.lv.demo.concurrency.sync.SyncTest - test2 4
00:52:46.178 [pool-1-thread-1] INFO com.lv.demo.concurrency.sync.SyncTest - test2 5
00:52:46.178 [pool-1-thread-1] INFO com.lv.demo.concurrency.sync.SyncTest - test2 6
00:52:46.178 [pool-1-thread-1] INFO com.lv.demo.concurrency.sync.SyncTest - test2 7
00:52:46.178 [pool-1-thread-1] INFO com.lv.demo.concurrency.sync.SyncTest - test2 8
00:52:46.178 [pool-1-thread-1] INFO com.lv.demo.concurrency.sync.SyncTest - test2 9
00:52:46.178 [pool-1-thread-3] INFO com.lv.demo.concurrency.sync.SyncTest - test2 0
00:52:46.178 [pool-1-thread-3] INFO com.lv.demo.concurrency.sync.SyncTest - test2 1
00:52:46.179 [pool-1-thread-3] INFO com.lv.demo.concurrency.sync.SyncTest - test2 2
00:52:46.179 [pool-1-thread-3] INFO com.lv.demo.concurrency.sync.SyncTest - test2 3
00:52:46.179 [pool-1-thread-3] INFO com.lv.demo.concurrency.sync.SyncTest - test2 4
00:52:46.179 [pool-1-thread-3] INFO com.lv.demo.concurrency.sync.SyncTest - test2 5
00:52:46.179 [pool-1-thread-3] INFO com.lv.demo.concurrency.sync.SyncTest - test2 6
00:52:46.179 [pool-1-thread-3] INFO com.lv.demo.concurrency.sync.SyncTest - test2 7
00:52:46.179 [pool-1-thread-3] INFO com.lv.demo.concurrency.sync.SyncTest - test2 8
00:52:46.179 [pool-1-thread-3] INFO com.lv.demo.concurrency.sync.SyncTest - test2 9
00:52:46.179 [pool-1-thread-2] INFO com.lv.demo.concurrency.sync.SyncTest - test2 0
00:52:46.179 [pool-1-thread-2] INFO com.lv.demo.concurrency.sync.SyncTest - test2 1
00:52:46.179 [pool-1-thread-2] INFO com.lv.demo.concurrency.sync.SyncTest - test2 2
00:52:46.179 [pool-1-thread-2] INFO com.lv.demo.concurrency.sync.SyncTest - test2 3
00:52:46.179 [pool-1-thread-2] INFO com.lv.demo.concurrency.sync.SyncTest - test2 4
00:52:46.179 [pool-1-thread-2] INFO com.lv.demo.concurrency.sync.SyncTest - test2 5
00:52:46.179 [pool-1-thread-2] INFO com.lv.demo.concurrency.sync.SyncTest - test2 6
00:52:46.179 [pool-1-thread-2] INFO com.lv.demo.concurrency.sync.SyncTest - test2 7
00:52:46.179 [pool-1-thread-2] INFO com.lv.demo.concurrency.sync.SyncTest - test2 8
00:52:46.179 [pool-1-thread-2] INFO com.lv.demo.concurrency.sync.SyncTest - test2 9

求解答

写回答

3回答