public static File mkdirsForFile(File file) {
  File dir = file.getParentFile();
  if (dir != null) try { // is null if file is in current dir
    dir.mkdirs();
  } catch (IOException e) {
    if (dir.isFile()) fail("Please delete the file " + f2s(dir) + " - it is supposed to be a directory!");
  }
  ret file;
}

public static S mkdirsForFile(S path) {
  mkdirsForFile(new File(path));
  ret path;
}