byte 转 十六进制

StringBuilder str = new StringBuilder();
        for (int i = 0; i < b.length; i++) {
          int v = b[i] & 0xFF;
          String hv = Integer.toHexString(v);
          if (hv.length() < 2) {
            str.append(0);
          }
          if (i == b.length-1) {
            str.append(hv);
          } else {
            str.append(hv + " ");
          }
        }
        String errorMsg = "处理消息时，收到了未经解码的字节数组【" + str + "】";