How to add a new column to a csv file using Apache Commons?

Question

I have a csv file that look like this:

name,age,total
xyz,22
abc,20

After processing the csv file should look like this:

name,age,total
xyz,22,100
abc,20,102

After running this code:

public class Converter {

    public static void main(String[] args) throws IOException {
        
        BufferedWriter writer = Files.newBufferedWriter(Paths.get(Constants.SAMPLE_CSV_FILE));
        CSVPrinter csvPrinter = new CSVPrinter(writer, CSVFormat.DEFAULT);
        
        csvPrinter.print(100);
        csvPrinter.print(102);
        
        csvPrinter.close();
    }

}

the output csv file becomes like this:

100
102

I want 100 and 102 to come under the total column. How can I do this?

You never actually read the existing data in. You have to read the data and add the field to every line and then write the updated line. — Jim Garrison
– Jim Garrison, Commented Dec 31, 2017 at 7:39

GalAbra · Accepted Answer · 2017-12-31 07:37:54Z

0

First of all, you shouldn't override your existing file. Hence, use the appending argument on the FileWriter constructor:

FileWriter pw = new FileWriter("C:\\exampleFile.csv",true);

Second, as you can see in your result, the CSVPrinter goes through your file by rows. If you want to add a new column, you actually need to iterate over each row and insert the new column's row data on every iteration, as explained thoroughly here

answered Dec 31, 2017 at 7:37

GalAbra

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