code: private Object registeredObjectRead(int handle) throws InvalidObjectException {
          Object res = objectsRead.get(handle - ObjectStreamConstants.baseWireHandle);
          if (res == UNSHARED_OBJ) {
              throw new InvalidObjectException("Cannot read back reference to unshared object");
          }
          return res;
      }
docs: Returns the previously-read object corresponding to the given serialization handle.
  @throws InvalidObjectException
  If there is no previously-read object with this handle