* for the data format.
   */
  static <K extends @Nullable Object, V extends @Nullable Object> void populateMap(
      Map<K, V> map, ObjectInputStream stream) throws IOException, ClassNotFoundException {
    int size = stream.readInt();
    populateMap(map, stream, size);
  }

  /**
   * Populates a map by reading an input stream, as part of deserialization. See {@link #writeMap}

     * allocation—not that any program should be deserializing hostile inputs to begin with!)
     */
    setDelegates(new EnumMap<>(keyTypeOrObjectUnderJ2cl), new HashMap<>());
    Serialization.populateMap(this, stream);
  }

  @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;

    valueTypeOrObjectUnderJ2cl = (Class<V>) requireNonNull(stream.readObject());
    setDelegates(
        new EnumMap<>(keyTypeOrObjectUnderJ2cl), new EnumMap<>(valueTypeOrObjectUnderJ2cl));
    Serialization.populateMap(this, stream);
  }

  @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;

    stream.defaultReadObject();
    int size = stream.readInt();
    init(16); // resist hostile attempts to allocate gratuitous heap
    Serialization.populateMap(this, stream, size);
  }

  // TODO(cpovirk): Should we have a serialVersionUID here?