CODEWITHSUNDEEP
javaarrayscsv
user2026615
user2026615

Reputation: 57

Export array values to csv file java

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.

Upvotes: 5

Views: 28333

Answers (5)

Dezso Gabos
Dezso Gabos

Reputation: 2452

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());
    }

Upvotes: 0

Marcelo Tataje
Marcelo Tataje

Reputation: 3871

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.

Upvotes: 12

ghdalum
ghdalum

Reputation: 891

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
}

Upvotes: 2

PermGenError
PermGenError

Reputation: 46398

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.

Upvotes: 4

Jacopofar
Jacopofar

Reputation: 3507

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.

Upvotes: 0

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