code: private void construct(DerValue derVal) throws IOException {
          if (derVal.isConstructed() && derVal.isContextSpecific()) {
              derVal = derVal.data.getDerValue();
              version = derVal.getInteger();
              if (derVal.data.available() != 0) {
                  throw new IOException("X.509 version, bad format");
              }
          }
      }
docs: Construct the class from the passed DerValue