import javax.mail.event.MessageCountAdapter; //导入依赖的package包/类
public void start(String folderName) throws Exception {
	executorService = Executors.newSingleThreadExecutor();

	Folder folder = mailService.ensureOpenFolder(folderName);

	folder.addMessageCountListener(new MessageCountAdapter() {
		@Override
		public void messagesAdded(MessageCountEvent event) {
			List<Message> messages = Arrays.asList(event.getMessages());

			handlers.forEach(handler -> handler.accept(messages));
		}
	});

	if (supportsIdle(folder)) {
		notificationWorker = new IdleNotificationWorker(mailService, (IMAPFolder) folder);
	} else {
		notificationWorker = new PollNotificationWorker(mailService, folder,
				configuration.getNotificationLookupTime());
	}

	LOGGER.debug("start notification service: {}", notificationWorker);

	executorService.submit(notificationWorker);
}
 

import javax.mail.event.MessageCountAdapter; //导入依赖的package包/类
private static void closeFolder(Folder folder, MessageCountAdapter messageListener) {
    if (folder != null) {
        if (messageListener != null) {
            folder.removeMessageCountListener(messageListener);
        }
        try {
            folder.close(false);
        }
        catch (MessagingException e) {
            Log.error("Error closing folder", e);
        }
    }
}