guava/src/com/google/common/collect/Serialization.java
static <K, V> void populateMultimap(Multimap<K, V> multimap, ObjectInputStream stream)
      throws IOException, ClassNotFoundException {
    int distinctKeys = stream.readInt();
    populateMultimap(multimap, stream, distinctKeys);
  }
static <K, V> void populateMultimap(Multimap<K, V> multimap, ObjectInputStream stream)
      throws IOException, ClassNotFoundException {
    int distinctKeys = stream.readInt();
    populateMultimap(multimap, stream, distinctKeys);
  }
Populates a multimap by reading an input stream, as part of deserialization. See {@link
#writeMultimap} for the data format.