如何在JFileChooser中保存csv文件？

Question

Hi I am not able to save a csv file.I am not even getting error in the write command.I have used FileChooser. And can any one explain the use of Approve option as i am new to swing.

if(e.getActionCommand()=="SaveTweet")
         {
        JFileChooser savePlaylistDialog = new JFileChooser();
        savePlaylistDialog.setSelectedFile(new File( ".csv"));
        int status = savePlaylistDialog.showSaveDialog(savePlaylistDialog);

        try {   
            if (status == JFileChooser.APPROVE_OPTION) {    
                File savePlaylist = savePlaylistDialog.getSelectedFile();                                            

        ICsvListWriter csvWriter = null;
         try { 
              TwitterProject obj=new TwitterProject();
             String [][] tweet=obj.generateBottweet(username,interval,Btweet,no);  

               csvWriter = new CsvListWriter(new FileWriter("savePlaylist"), 

           CsvPreference.STANDARD_PREFERENCE);

               for (int i = 0; i < tweet.length; i++) {
               csvWriter.write(tweet[i]);
             }

      } catch (IOException e1) {
                e1.printStackTrace(); 
      } finally {
         try {
         System.out.println("closing file");
         csvWriter.close();
                } catch (IOException e1) {
             }
      }

      } else if (status == JFileChooser.CANCEL_OPTION) {
                // User has pressed cancel button
  }
 } catch (Exception ex) {
          JOptionPane.showMessageDialog(null, "File could not be written, try again.");
        }
    }
 }

Answer 1

Two things jump out...

First, you comparing Object reference of String instead of contents...

if(e.getActionCommand()=="SaveTweet")

Will very rarely be true, as the Object references will most likely never be equal, instead, you should try using something like...

if("SaveTweet".equals(e.getActionCommand()))

Which will compare the contents of the two String s, but will also guard against possible NullPointerException s...

Second, you are ignoring the File the the user selected, for example, you get a reference to the file the user selects using...

File savePlaylist = savePlaylistDialog.getSelectedFile();

But then you create a FileWriter which simply uses a String value...

csvWriter = new CsvListWriter(new FileWriter("savePlaylist"));

Instead, should try using something like...

csvWriter = new CsvListWriter(new FileWriter(savePlaylist));

Which will write the contents to the file that the user selects...

ps- I would also drop...

savePlaylistDialog.setSelectedFile(new File( ".csv"));

As it doesn't actually make sense, I doubt there would be file called .csv ...or more to the point, it's highly unlikely...

Answer 2

To compare String objects in java use .equals() method instead of "==" operator

change

if(e.getActionCommand()=="SaveTweet")

to

if("SaveTweet".equals(e.getActionCommand()))

if you want to ignore the case use like below code

if("SaveTweet".equalsIgnoreCase(e.getActionCommand()))

Answer 3

Did you also test the writing method? Which implementation of csvwriter do you use? In some cases (com.csvwriter) you need to call flush() before close().