code: public static String _2_16(byte[] bytes) {
  
          if (bytes == null || bytes.length == 0)
              return null;
  
          StringBuilder sb = new StringBuilder();
          for (byte aByte : bytes) {
              String hex = Integer.toHexString(aByte & 0xFF);
              if (hex.length() == 1) {
                  hex = '0' + hex;
              }
              sb.append(hex.toUpperCase());
          }
          return sb.toString();
      }
docs: 二进制转十六进制
  @param bytes [ellipsis]
  @return [ellipsis]