Question

我打算使用 parallelStream 执行一些耗时的代码。这似乎工作良好，但我有一个问题，即后续代码未执行：

@PreDestroy
public void tearDown() {
    final int mapSize = eventStreamProcessorMap.size();
    LOG.info("There are {} subscriptions to be stopped!", mapSize);

    final long start = System.currentTimeMillis();
    LocalTime time = LocalTime.now();

    final AtomicInteger count = new AtomicInteger();
    eventStreamProcessorMap.entrySet().parallelStream().forEach(entry -> {
        final Subscription sub = entry.getKey();
        final StreamProcessor processor = entry.getValue();

        LOG.info("Attempting to stop subscription {} of {} with id {} at {}", count.incrementAndGet(), mapSize, sub.id(), LocalTime.now().format(formatter));

            LOG.info("Stopping processor...");
            processor.stop();
            LOG.info("Processor stopped.");

            LOG.info("Removing subscription...");
            eventStreamProcessorMap.remove(sub);
            LOG.info("Subscription {} removed.", sub.id());

        LOG.info("Finished stopping processor {} with subscription {} in ParallelStream at {}: ", processor, sub, LocalTime.now().format(formatter));
        LOG.info(String.format("Duration: %02d:%02d:%02d:%03d (hh:mm:ss:SSS)",
                TimeUnit.MILLISECONDS.toHours(System.currentTimeMillis() - start),
                TimeUnit.MILLISECONDS.toMinutes(System.currentTimeMillis() - start)%60,
                TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis() - star0)%60,
                TimeUnit.MILLISECONDS.toMillis(System.currentTimeMillis() - start)%1000));
        LOG.info("--------------------------------------------------------------------------");
    });

    LOG.info("Helloooooooooooooo?????");
    LOG.info(String.format("Overall shutdown duration: %02d:%02d:%02d:%03d (hh:mm:ss:SSS)",
            TimeUnit.MILLISECONDS.toHours(System.currentTimeMillis() - start),
            TimeUnit.MILLISECONDS.toMinutes(System.currentTimeMillis() - start)%60,
            TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis() - start)%60,
            TimeUnit.MILLISECONDS.toMillis(System.currentTimeMillis() - start)%1000));
    LOG.info("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx");
}

parallelStream处理后的代码未执行：

LOG.info("Helloooooooooooooo?????");

永远不会出现在日志中。为什么不呢？

Answer 1

这是由eventStreamProcessorMap.remove(sub);引起的（您现在通过所做的编辑将其从代码中删除）。您正在通过Map entrySet（eventStreamProcessorMap）流式传输并从中删除元素-这是不允许的，这就是为什么要获得ConcurrentModificationException的原因。

如果您确实要在迭代时删除，请使用Iterator或map.entrySet().removeIf(x -> {...})

为什么使用parallelStream之后的编码器未执行？

1 个答案: