//  RETURNS STRING WITH ALL THE VEHICLES OF THE USER
    @Override
    public String printVehicles() {
        StringBuilder output = new StringBuilder(String.format(USER_HEADER, username));

        if (vehicles.isEmpty()) {
            output.append("\n");
            output.append(NO_VEHICLES_HEADER);
        } else {
            for (int i = 0; i < vehicles.size(); i++) {
                // PRINTING VEHICLE
                output.append("\n");
                output.append(i + 1).append(vehicles.get(i).toString());
                // PRINTING THE COMMENTS OF THE CURRENT VEHICLE
                if (vehicles.get(i).getComments().isEmpty()) {
                    output.append(NO_COMMENTS_HEADER);
                } else {
                    output.append(vehicles.get(i).printComments());
                }
            }
        }
        return output.toString();
    }