code: private String read(String path) throws IOException {
          StringBuffer sb = new StringBuffer();
          String tempStr;
          File file = new File(path);
          // 如果文件不存在，读取失败
          if (!file.exists()) throw new FileNotFoundException();
          FileInputStream fis = new FileInputStream(file);
          BufferedReader br = new BufferedReader(new InputStreamReader(fis));
          while ((tempStr = br.readLine()) != null) sb.append(tempStr);
          return sb.toString();
      }
docs: 根据文件路径读取文件内容
  [仅做参考]
  @param path 文件路径
  @return 文件内容
  @throws IOException 读取失败