Export array values to csv file java

Question

I just need help exporting array elements to a csv file. I don't know what's wrong with my code. Any help is gladly appreciated. Thanks.

for (int index = 0; index < cols.length; index++)
{
    FileWriter fw = new FileWriter(newFileName);
    if (index == cols.length - 1)
    {
        fw.append(cols[index]);
    }
    else
    {
        fw.append(cols[index]);
        fw.append(",");
    }

}

When I run this. Nothing happens to my csv file. Infact, it wipes everything of. Please help.

Did you do a `fw.close();` at the end of your code? Also, you should declare `fw` outside of your loop, otherwise your file will be rewritten for each column. — Bastien Jansen, Mar 12 '13 at 14:46

score 12 · Accepted Answer · edited Jul 28 '18 at 06:03

12

Assuming you're storing String in your array, I post an alternative solution:

BufferedWriter br = new BufferedWriter(new FileWriter("myfile.csv"));
StringBuilder sb = new StringBuilder();

// Append strings from array
for (String element : array) {
 sb.append(element);
 sb.append(",");
}

br.write(sb.toString());
br.close();

Best regards.

edited Jul 28 '18 at 06:03

VILLAIN bryan

701
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answered Mar 12 '13 at 14:52

Marcelo Tataje

3,849
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1

so if you agree with this answer, please mark it as the right one for you in order to make this post "closed" and maybe people who have the same problem can see that this is a reliable answer to trust in. It was nice to help you. Best regards. – Marcelo Tataje Mar 13 '13 at 15:44

PermGenError · Answer 2 · 2013-03-12T14:52:11.780

4

you need to flush the written data, close your FileWriter.

      finally {
        fw.close(); // close will automatically flush the data 
      }

Also, use BufferedWriter or PrintWriter instead as they are highly efficient and evolved than FileWriter.

Btw, declare the FileWriter outta your for loop. Currently it will overwrite the column for each iteration.

edited Mar 12 '13 at 14:52

answered Mar 12 '13 at 14:45

PermGenError

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Is flush necessary? Just reading the java docs which suggest that flush is called as part of close: _Closes the stream, flushing it first._ – Chris Knight Mar 12 '13 at 14:46
@ChrisKnight true, just realized . :) – PermGenError Mar 12 '13 at 14:47

score 2 · Answer 3 · answered Mar 12 '13 at 14:54

2

If you use the more effective BufferedWriter combined with try-with-resources the writer is automatically closed. (In Java 7)

try {BufferedWriter br = new BufferedWriter(new FileWriter(newFileName)) {
    // your code
}

answered Mar 12 '13 at 14:54

ghdalum

891
5
17

score 0 · Answer 4 · answered Mar 12 '13 at 14:49

0

You have to use

 FileWriter fw = new FileWriter(newFileName,true);

to append content, or the file will be overwritten.

The name of the append method can be misleading, in fact it append to an internal buffer, not to the file content.

answered Mar 12 '13 at 14:49

Jacopofar

3,407
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score 0 · Answer 5 · answered Dec 14 '18 at 17:53

The best way would be to use a CSVWriter. If you have a maven project add this as a dependency:

  <dependency>
      <groupId>com.opencsv</groupId>
      <artifactId>opencsv</artifactId>
      <version>4.4</version>
  </dependency>

And then you can use it like this:

try {
        //the list that contains the String arrays
        List<String[]> whatever = new ArrayList<>();
        CSVWriter writer = new CSVWriter(new FileWriter(csvFilename));
        String[] header = "Name,Age,Height,etc..".split(",");
        writer.writeNext(header);
        writer.writeAll(whatever, true); //And the second argument is boolean which represents whether you want to write header columns (table column names) to file or not.
        writer.close();
        System.out.println("CSV file created succesfully.");
    } catch (Exception e) {
        System.out.println("exception :" + e.getMessage());
    }

Export array values to csv file java

5 Answers5

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