parser

//CsvConverter
public class CsvConverter {

    public static void convert(String file, List<Order> out) {
        BlockingQueue<String> data = new LinkedBlockingQueue<>();
        ReadService.readFile("src/main/resources/" + file, data);
        CsvMapper mapper = new CsvMapper();
        CsvSchema schema = CsvSchema.builder()
                .addColumn("orderId")
                .addColumn("amount")
                .addColumn("currency")
                .addColumn("comment")
                .build();

        data.parallelStream().forEachOrdered(s -> {
            try {
                out.add((Order) mapper
                        .readerFor(Order.class)
                        .with(schema)
                        .readValues(s).nextValue());
            } catch (IOException e) {
                e.printStackTrace();
            }
        });
    }
}

//JsonConverter
public class JsonConverter {

    public static void convert(String file, List<Order> out) {
        BlockingQueue<String> data = new LinkedBlockingQueue<>();
        ReadService.readFile("src/main/resources/" + file, data);
        ObjectMapper mapper = new ObjectMapper();
        data.parallelStream().forEachOrdered(s -> {
            try {
                out.add(mapper.readValue(s, Order.class));
            } catch (JsonProcessingException e) {
                e.printStackTrace();
            }
        });
    }
}
//ReadService
public class ReadService {

    public static void readFile(String fileName, BlockingQueue<String> data) {
        try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {
            for (String line; (line = br.readLine()) != null; ) {
                data.add(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

//App
@SpringBootApplication
public class ParsingProjApplication {

    public static void main(String[] args) {
        SpringApplication.run(ParsingProjApplication.class, args);
        BlockingQueue<String> data = new LinkedBlockingQueue<>();
        List<String> permittedExt = new ArrayList<String>(Arrays.asList("json", "csv"));
        List<Order> res = new ArrayList<>();
        for (String arg : args) {
            String ext = null;
            try {
                ext = FilenameUtils.getExtension(arg);
                if (!permittedExt.contains(ext))
                    throw new IllegalArgumentException();
                System.out.println(ext);
            } catch (IllegalArgumentException e) {
                System.out.println("File format is not correct");
            }
            if (Objects.equals(ext, "json")){
                JsonConverter.convert(arg, res);
            } else {
                CsvConverter.convert(arg, res);
            }
        }
        System.out.println(res);
    }
}