private File askForFileName() {
		
		while (true){
			int option = fileChooser.showSaveDialog(this);
			if (option == JFileChooser.APPROVE_OPTION){
				File file = fileChooser.getSelectedFile();
				
				if (file.exists()){
					if (JOptionPane.showConfirmDialog(this, "El archivo ya existe, desea sobreescribir?") == JOptionPane.YES_OPTION){
						return file;
					}
				} else {
					return file;
				}
			} else if (option == JFileChooser.CANCEL_OPTION){
				return null;
			}
		}
	}