ifdef renameFile_useNIO
endifdef

static boolean renameFile(File a, File b) {
  if (!a.exists()) fail("Source file not found: " + f2s(a));
  if (b.exists()) fail("Target file exists: " + f2s(b));
  mkdirsForFile(b);
  ifdef renameFile_useNIO
    Files.move(a.toPath(), b.toPath());
  endifdef
  ifndef renameFile_useNIO
  ret a.renameTo(b);
  endifndef
}