private HashMap<Integer, String> LoadTimestampDiffsFromFile() {
        try (
                InputStream file = new FileInputStream("timestamps.ser");
                InputStream buffer = new BufferedInputStream(file);
                ObjectInput input = new ObjectInputStream(buffer);) {
            //deserialize the List
            HashMap<Integer, String> hashMap = (HashMap<Integer, String>) input.readObject();
            return hashMap;

        } catch (ClassNotFoundException ex) {
            logger.error("Cannot deserialize object. Class not found." + ex.getMessage());
        } catch (IOException ex) {
            logger.error("Cannot deserialize object: " + ex.getMessage());
        }
        return new HashMap<>();
    }