code: private synchronized void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
          in.defaultReadObject();
  
          // the transient _nameMap is null after an instance of
          // NameService has been serialized.
          if (_nameMap == null) {
              _nameMap = new HashMap();
          }
      }
docs: Deserialize an instance of this class.
  @param in ObjectInputStream to deserialize from.
  @throws IOException
  @throws ClassNotFoundException