Pippo.java

package com.thomsonreuters.solutions.baml.support;

import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVPrinter;

import java.io.BufferedWriter;
import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.*;
import java.util.stream.Collectors;

public class FilterTest {

    private static final String SAMPLE_CSV_FILE = "./sample.csv";

    public static void main(String[] args) throws IOException {
        Map<String, String> data = new LinkedHashMap<>();
        data.put("K1", "V1");
        data.put("K2", "V2");
        data.put("K4", "V4");
        data.put("K3", "V3");

        Set<String> header = data.keySet();
        try (
                Writer writer = new StringWriter(0);
                CSVPrinter csvPrinter = new CSVPrinter(writer, CSVFormat.DEFAULT
                        .withHeader(header.toArray(new String[0])));

        ) {
            String[] record = header.stream().map(h -> data.getOrDefault(h, "")).toArray(String[]::new);
            csvPrinter.printRecord(record);
            csvPrinter.flush();
            System.err.println(writer.toString());
        }
    }
}