code: public BufferedOutputStream getOutputStream() throws IORuntimeException {
  		try {
  			return new BufferedOutputStream(new FileOutputStream(FileUtil.touch(file)));
  		} catch (IOException e) {
  			throw new IORuntimeException(e);
  		}
  	}
docs: 获得一个输出流对象
  
  @return 输出流对象
  @throws IORuntimeException IO异常