public static @NotNull String getNextAvailableName(@NotNull VirtualFile dir, @NotNull String prefix, @NotNull String extension) {
    String dotExt = PathUtil.makeFileName("", extension);
    String fileName = prefix + dotExt;
    int i = 1;
    while (dir.findChild(fileName) != null) {
      fileName = prefix + "_" + i + dotExt;
      i++;
    }
    return fileName;
  }
public static @NotNull String getNextAvailableName(@NotNull VirtualFile dir, @NotNull String prefix, @NotNull String extension)