/**
  * uses a filechooser to get the name of the export file
  *
  * @return
  */
 public File getOutputFile() {
   File file;
   FileChooser fc = new FileChooser(FileChooserBase.SAVE, pref.getExportPath(expName));
   fc.setTitle("Select target file:");
   fc.addMask(mask);
   if (fc.execute() != FormBase.IDCANCEL) {
     file = fc.getChosenFile();
     pref.setExportPath(expName, file.getPath());
     return file;
   } else {
     return null;
   }
 }