List<String> labels = new ArrayList<String>();
ListLabelsResponse listResponse = service.users().labels().list(userId).execute();
for (Label label : listResponse.getLabels()) {
Label countLabel = service.users().labels().get(userId, label.getId()).execute();
if (countLabel.getName().equalsIgnoreCase("UNREAD"))
unreadId = countLabel.getId();
}
List<String> add = new ArrayList<String>();
List<String> remove = new ArrayList<String>();
remove.add(unreadId);
modifyMessage(service, userId, message.getId(), add, remove);
public static void modifyMessage(Gmail service, String userId, String messageId,
List<String> labelsToAdd, List<String> labelsToRemove) throws IOException {
ModifyMessageRequest mods = new ModifyMessageRequest().setAddLabelIds(labelsToAdd)
.setRemoveLabelIds(labelsToRemove);
Message message = service.users().messages().modify(userId, messageId, mods).execute();
}