public String getCnameFromCid(int cid) {
		if (classesMapCidToCname == null) {
			System.out.println("Ŀӳûи");
			return null;
		} else {
			if (classesMapCidToCname.containsKey(cid)) {
				String cname = (String) classesMapCidToCname.get(cid);
				return cname;
			} else {
				System.out.print("ĿϵвcidΪ " + cid + " Ľڵ");
				return null;
			}
		}
	}