public List<String> alloc(String filename, int num_chunks) {
		int chunkloc = 1;
		String chunk_uuid;
		List<String> chunk_uuids = new ArrayList<String>();
		for (int i = 0; i < num_chunks; i++) {
			chunk_uuid = UUID.randomUUID().toString();
			chunk_uuids.add(chunk_uuid);
			chunktable.put(chunk_uuid, chunkloc);
			chunkloc = chunkloc % num_datanodes + 1;
		}
		filetable.put(filename, chunk_uuids);
		// ӳ䡢Ľӡ
		Iterator it = (Iterator) filetable.entrySet().iterator();
		while (it.hasNext()) {
			@SuppressWarnings("unchecked")
			Map.Entry<String, List<String>>  me = (Entry<String, List<String>> ) it.next();
			System.out.println(me.getKey() + "/" + me.getValue());
		}
		Iterator it2 = chunktable.entrySet().iterator();
		while (it2.hasNext()) {
			@SuppressWarnings("unchecked")
			Map.Entry<String, List<String>>  me2 = (Entry<String, List<String>> ) it2.next();
			System.out.println(me2.getKey() + "/" + me2.getValue());
		}
		return chunk_uuids;
	}