Automatically close & flush

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 NIO.2 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();
}
// At this point, the `CSVPrinter` is automatically closed. 
// And, ➡️ the `BufferedWriter` is automatically closed and flushed. 

Ok figured it out. I changed the maps to LinkedHashMap to retain order then did this:

   try (BufferedWriter writer = Files.newBufferedWriter(Paths.get(outputFile));
        CSVPrinter csvPrinter = new CSVPrinter(writer, CSVFormat.DEFAULT
        .withHeader(Header.class));)
   {

        for (Map<Header, String> val : output)
        {
            csvPrinter.printRecord(val.values().toArray());
        }

        csvPrinter.flush();

    } catch (IOException ex)
    {
        Logger.getLogger(TestCSV.class.getName()).log(Level.SEVERE, null, ex);
    }