code: private void writeObject(ObjectOutputStream stream) throws IOException {
      stream.writeInt(_capacity);
      stream.writeInt(_size);
      int count = 0;
      EntryImpl<K, V> entry = _mapFirst;
      while (entry != null) {
        stream.writeObject(entry._key);
        stream.writeObject(entry._value);
        count++;
        entry = entry._after;
      }
      if (count != _size) { throw new IOException("FastMap Corrupted"); }
    }
docs: Requires special handling during serialization process.
  
  @param stream the object output stream.
  @throws IOException if an I/O error occurs.