public @NotNull PageImpl lookupOrCreate(final int pageIndex,
                                          final @NotNull IntFunction<PageImpl> uninitializedPageFactory) throws IOException {
    final PageImpl page = findPageOrInsertionIndex(this.pages, pageIndex, /*insertionIndexRef: */null);
    if (page != null) {
      return page;
    }
    return insertNewPage(pageIndex, uninitializedPageFactory);
  }
public @NotNull PageImpl lookupOrCreate(final int pageIndex,
                                          final @NotNull IntFunction<PageImpl> uninitializedPageFactory)