public static byte[] writeListToByteArray(List<? extends Writable> writableList) {
		ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
		DataOutput output = new DataOutputStream(outputStream);
		try {
			output.writeInt(writableList.size());
			for (Writable writable : writableList) {
				writable.write(output);
			}
		} catch (IOException e) {
			throw new IllegalStateException("직렬화할 수 없습니다: IOException", e);
		}
		return outputStream.toByteArray();
	}