Why is the coder after using parallelStream not executed? - java-stream

Question

I intend to execute some time consuming code using using parallelStream. This seems to work well but I have the problem that the subsequent code is not executed:
#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");
}
The code after the parallelStream processing is not executed:
LOG.info("Helloooooooooooooo?????");
does never appear in the log. Why not?

Answer 1

This is caused by eventStreamProcessorMap.remove(sub); (which you have removed from the code now with the edit that you made). You are streaming over a Map entrySet (eventStreamProcessorMap) and removing elements from it - this is not allowed, that is why you get that ConcurrentModificationException.
If you really want to remove while iterating, use an Iterator or map.entrySet().removeIf(x -> {...})