java class to read csv files

Question

Here is my class to read a csv file and I was wondering if there is any improvements that I should do. I feel there are some performance improvements or in exception handling because I just took IO exceptions.

package com.mypackage.utils;
import com.opencsv.CSVParserBuilder;
import com.opencsv.CSVReader;
import com.opencsv.CSVReaderBuilder;
import com.opencsv.enums.CSVReaderNullFieldIndicator;

import java.io.File;
import java.io.IOException;
import java.nio.file.Paths;
import java.util.*;

public class FileReader {

    private String path;
    private CSVReader reader;
    private List<String> linesList;
    private Set<List<String>> splitLinesSet;

    public FileReader(String path) {
        this.path = path;
    }

    public boolean readFile() {

        this.splitLinesSet = new HashSet<>();

        try {
            File file = Paths.get(path).toFile();
            reader = new CSVReaderBuilder(new java.io.FileReader(file))
                    .withCSVParser(new CSVParserBuilder()
                            .withSeparator('|')
                            .withFieldAsNull(CSVReaderNullFieldIndicator.NEITHER).build())
                    .build();
            read();
            reader.close();
        } catch (IOException e) {
            System.err.println("Error in reading CSV: " + e.getMessage());
            return false;
        }

        return true;
    }

    public Set<List<String>> getSplitLinesSet() {
        return splitLinesSet;
    }

    private void read() throws IOException {
        String[] lines;
        while ((lines = reader.readNext()) != null) {
            linesList = new ArrayList<>();
            Collections.addAll(linesList, lines);
            splitLinesSet.add(linesList);
        }
    }
}

Answer 1

I tend to advocate not passing things around which need to be closed, thus my advice is:

• inline the read method
• remove the reader field, and
• ... declare the same as a local variable
• perferably, declare that local reader variable in a try-with-resources block and throw out the explicit close()-call

Note that these changes are just about robustness and maintainability and will not affect performance or error handling.

Edit, after the comment asking for code edit. (Note: sorry, I am a newbie in the code review community, I hope this does not break any principle here.)

public class FileReader {

    private String path;
    private List<String> linesList;
    private Set<List<String>> splitLinesSet;

    public FileReader(String path) {
        this.path = path;
    }

    public boolean readFile() {

        this.splitLinesSet = new HashSet<>();
        File file = Paths.get(path).toFile();

        try (
            CSVReader reader = new CSVReaderBuilder(new java.io.FileReader(file))
                    .withCSVParser(new CSVParserBuilder()
                            .withSeparator('|')
                            .withFieldAsNull(CSVReaderNullFieldIndicator.NEITHER).build())
                    .build();
            ) {
            String[] lines;
            while ((lines = reader.readNext()) != null) {
                linesList = new ArrayList<>();
                Collections.addAll(linesList, lines);
                splitLinesSet.add(linesList);
            }
        } catch (IOException e) {
            System.err.println("Error in reading CSV: " + e.getMessage());
            return false;
        }

        return true;
    }

    public Set<List<String>> getSplitLinesSet() {
        return splitLinesSet;
    }
}

Note: this was just syntactic shuffling of lines in a text editor - I have not put this through an IDE or a compiler, but I think it shows the principles.

Answer 2

FileReader should be avoided, because it relies on a default encoding. We should specify explicitly the encoding used.

CSVParser parser = new CSVParserBuilder().withSeparator('|').build();

try (BufferedReader br = Files.newBufferedReader(myPath, 
        StandardCharsets.UTF_8);
        CSVReader reader = new CSVReaderBuilder(br).withCSVParser(parser)
                .build()) {
...