private String openChooser() {
		JFileChooser fileChooser = new JFileChooser();
		//ӹ˵ַ
		FileNameExtensionFilter ff = new FileNameExtensionFilter( null, "txt");
		fileChooser.setFileFilter(ff);
		int option = fileChooser.showOpenDialog(null);
		if(option == JFileChooser.APPROVE_OPTION){
		//ȡϢ
		return fileChooser.getSelectedFile().getPath();
		}
		return "";
	}