code: public static byte[] read2ByteArray(String filePath) {
          try {
              BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream(new File(filePath)));
              byte[] byteArr = new byte[bufferedInputStream.available()];
              bufferedInputStream.read(byteArr);
              bufferedInputStream.close();
              return byteArr;
          } catch (FileNotFoundException e) {
              e.printStackTrace();
          } catch (IOException e) {
              e.printStackTrace();
          }
          return null;
      }
docs: 将指定文件读成byte数据
  @param filePath
  @return