code: public static File[] chooseFiles(String title, File currentDir) {
  		if (currentDir == null) currentDir = new File(".");
  		JFileChooser fileChooser = new JFileChooser();
  		fileChooser.setCurrentDirectory(currentDir);
  		fileChooser.setDialogTitle(title);
  		fileChooser.setMultiSelectionEnabled(true);
  		int result = fileChooser.showOpenDialog(null);
  		if (result == JFileChooser.APPROVE_OPTION) {
  			return fileChooser.getSelectedFiles();
  		}
  		return null;
  	}
docs: Open a {@link javax.swing.JFileChooser} with multi-selection enabled, and return the selected file(s), or null if closed or cancelled.
  
  @param title      The title of the file-chooser window.
  @param currentDir The root directory. If null, {@code new File(".")} will be used.
  @return The chosen file(s), or null if none was chosen.