private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
  in.defaultReadObject();
  if (server == null) {
    throw new InvalidObjectException("null server");
  }
 else   if (lease == null) {
    throw new InvalidObjectException("null lease");
  }
}

private void readObject ( ObjectInputStream in ) throws IOException , ClassNotFoundException { in . defaultReadObject ( ) ; if ( server == null ) { throw new InvalidObjectException ( "null server" ) ; } else if ( lease == null ) { throw new InvalidObjectException ( "null lease" ) ; } }
verifies that member fields are non - null .
