* k <= i < n}.
   *
   * <p>After this method returns, {@code elements} will contain no duplicates, but {@code elements}
   * may be the real array backing the returned set, so do not modify it further.
   *
   * <p>{@code elements} may contain only values of type {@code E}.
   *

  public int hashCode() {
    int hashCode = 1;
    int n = size();
    for (int i = 0; i < n; i++) {
      hashCode = 31 * hashCode + get(i).hashCode();

      hashCode = ~~hashCode;
      // needed to deal with GWT integer overflow
    }
    return hashCode;
  }

  /*
   * Serializes ImmutableLists as their logical contents. This ensures that