Converts multiple csv files in a singe json file

CsvToJson.java

package com.sai;

import com.google.common.collect.MultimapBuilder;
import com.google.common.collect.SetMultimap;
import com.google.gson.GsonBuilder;
import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVParser;
import org.apache.commons.csv.CSVRecord;

import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;
import java.util.List;
import java.util.stream.Stream;

public class CsvToJson {

    public static List<CSVRecord> getCsvRecords(String filePath) {
        try (Reader in = new FileReader(filePath)) {
            Iterable<CSVRecord> records = CSVFormat.EXCEL.withFirstRecordAsHeader().parse(in);
            return ((CSVParser) records).getRecords();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static String convertToJson(Object obj) {
        return new GsonBuilder().setPrettyPrinting().create().toJson(obj);
    }

    public static File[] getCsvFiles(String csvFileDir) {
        return new File(csvFileDir).listFiles((d, name) -> name.toLowerCase().endsWith(".csv"));
    }

    public static void main(String[] args) {
        SetMultimap<String, String> setMultimap = MultimapBuilder.hashKeys().hashSetValues().build();
        String csvFileDir = "./src/main/resources/data";
        Stream.of(getCsvFiles(csvFileDir)).forEach(file -> {
            List<CSVRecord> records = getCsvRecords(file.getAbsolutePath());
            records.forEach(record -> record.toMap().forEach(setMultimap::put));
        });

        System.out.println(convertToJson(setMultimap.asMap()));
    }
}