code: public static String readFile(File file) throws IOException {
          StringBuilder content = new StringBuilder();
          String line;
          try (BufferedReader reader = new BufferedReader(new FileReader(file))) {
              while ((line = reader.readLine()) != null) {
                  content.append(line).append("\r\n");
              }
          }
          return content.toString();
      }
docs: 读取文件
  
  @param file 文件
  
  @return {@link String}
  
  @throws IOException 异常