SavedStateHandle.java

public final class SavedStateHandle {
  static SavedStateHandle createHandle(@Nullable Bundle restoredState,
    @Nullable Bundle defaultState) {
    ...
    Map<String, Object> state = new HashMap<>();
    if (defaultState != null) {
      for (String key : defaultState.keySet()) {
        state.put(key, defaultState.get(key));
      }
    }
    ...
    ArrayList keys = restoredState.getParcelableArrayList(KEYS);
    ArrayList values = restoredState.getParcelableArrayList(VALUES);
    ...
    for (int i = 0; i < keys.size(); i++) {
      state.put((String) keys.get(i), values.get(i));
    }
    return new SavedStateHandle(state);
  }
}