private static Map<Long, Integer> list2Map(List<Long> ids) {
		Map<Long, Integer> map = new HashMap<Long, Integer>();
		for (Long id : ids) {
			if (map.containsKey(id)) {
				map.put(id, map.get(id) + 1);
			} else {
				map.put(id, 1);
			}
		}
		return map;
	}