Java - Write CSV File with Apache.commons.csv

Question

I'm using the apache.commons.csv library in Java. I'm reading a CSV file from a web page with this code:

InputStream input = new URL(url).openStream();
Reader reader = new InputStreamReader(input, "UTF-8");
        
defaultParser = new CSVParser(reader, CSVFormat.DEFAULT);
excelParser = new CSVParser(reader, CSVFormat.EXCEL.withHeader()); 
        
defaultParsedData = defaultParser.getRecords();
excelParsedData = excelParser.getRecords();

However, I can't find a method in this library to easily write this file to my computer in order to open it up and read from it later on.

I tried this code to save the file.

String outputFile = savePath+".csv";
CSVPrinter csvFilePrinter = null;
CSVFormat csvFileFormat = CSVFormat.EXCEL.withHeader();
FileWriter fileWriter = new FileWriter(outputFile);
csvFilePrinter = new CSVPrinter(fileWriter, csvFileFormat);

for (CSVRecord csvRecord : excelParser) {
    for(String dataPoint: csvRecord){
        csvFilePrinter.print(dataPoint);
    }
    csvFilePrinter.print('\n');
}

fileWriter.flush();
fileWriter.close();
csvFilePrinter.close();

However, when I try to read the file with this code, nothing prints out:

InputStream input = new FileInputStream(cvsFilePath);
Reader reader = new InputStreamReader(input, "UTF-8");
        
CSVParser load = new CSVParser(reader, CSVFormat.EXCEL);
//TEST THAT IT WORKED
java.util.List<CSVRecord> testlist = load.getRecords();
CSVRecord dataPoint = testlist.get(0);
System.out.println("print: " + dataPoint.get(0));

This only prints out "print: " If I add

System.out.println("print: " + dataPoint.get(1));

it gives a

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1

When I open the saved CSV file with notepad there is a blank line and then:

2016-03-04,714.98999,716.48999,706.02002,710.890015,1967900,710.890015," ",2016-03-03,718.679993,719.450012,706.02002,712.419983,1956800,712.419983," ",2016-03-02,719.00,720.00,712.00,718.849976,1627800,718.849976,"

@Berger Well, I'm sure I didn't write the code correctly. The file that it saves is not the same file that it read from a webpage. I figured there should be a simple built-in method in Apache Commons to save a file that was in a parser, but I couldn't find one, so I attempted to do it that way. — jonbon
– jonbon, Commented Mar 29, 2016 at 15:52
@Berger I get an error "File not loaded completely" when I try to open it in Excel. I updated the OP with the code I'm using to read from the saved file. — jonbon
– jonbon, Commented Mar 29, 2016 at 16:01
Open it with a simple text editor (notepad, whatever..) and paste the content in your question . — Arnaud
– Arnaud, Commented Mar 29, 2016 at 16:03

Arnaud · Accepted Answer · 2016-03-29 16:15:32Z

17

It looks like you are printing all the records on the same line .

Other methods like printRecords will be more helpful :

String outputFile = savePath+".csv";
CSVPrinter csvFilePrinter = null;
CSVFormat csvFileFormat = CSVFormat.EXCEL.withHeader();
FileWriter fileWriter = new FileWriter(outputFile);
csvFilePrinter = new CSVPrinter(fileWriter, csvFileFormat);

csvFilePrinter.printRecords(excelParser.getRecords());


fileWriter.flush();
fileWriter.close();
csvFilePrinter.close();

answered Mar 29, 2016 at 16:15

Arnaud

17.6k3 gold badges34 silver badges46 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Basil Bourque · Accepted Answer · 2025-02-26 19:47:36Z

The Answer by Arnaud is correct and good. Here is a variation, shorter and more modern.

Here we:

Use the Path, File, and Files classes offered by modern Java to make easier work of file-handling.
Use a BufferedWriter for better performance with large amounts of data.
Specify the character encoding to be used. Usually UTF-8 is the best. If you do not understand, read this.
Include the necessary try-catches for file-related exceptions.
Add try-with-resources syntax to auto-close the file.
Skip the explicit flushing, as the buffered writer will be flushed automatically as part of auto-closing the BufferedWriter and CSVPrinter. To quote the Javadoc, calling java.io.Writer::close “Closes the stream, flushing it first.”.

Code:

CSVFormat format = CSVFormat.EXCEL.withHeader();
Path path = Paths.get( savePath + ".csv" );
try 
(
        BufferedWriter writer = Files.newBufferedWriter( path , StandardCharsets.UTF_8 ) ;
        CSVPrinter printer = new CSVPrinter( writer , format ) ;
)
{
    printer.printRecords( excelParser.getRecords() );
} 
catch ( IOException e )
{
    e.printStackTrace();
}

Edit: There was a bracket missing.

Ion Freeman · Accepted Answer · 2018-01-04 17:48:50Z

2

Have you tried flushing and closing the CSVPrinter, not the FileWriter?

answered Jan 4, 2018 at 17:48

Ion Freeman

5605 silver badges21 bronze badges

1 Comment

katwekibs Over a year ago

i was not closing the CSVPrinter thank you @ionFreeman.

Collectives™ on Stack Overflow

Java - Write CSV File with Apache.commons.csv

3 Answers 3

Comments

Comments

1 Comment

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

1 Comment

Linked

Related