static S loadTextFile(S fileName) {
  return loadTextFile(fileName, null);
}

static S loadTextFile(File f, S defaultContents, S encoding default "UTF-8") ctex {
  ifndef LeanMode
  checkFileNotTooBigToRead(f);
  endifndef
  if (f == null || !f.exists()) ret defaultContents;

  FileInputStream fileInputStream = new FileInputStream(f);
  InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream, encoding);
  ret loadTextFile(inputStreamReader);
}

public static String loadTextFile(File fileName) {
  return loadTextFile(fileName, null);
}

static S loadTextFile(S fileName, String defaultContents) {
  ret fileName == null ? defaultContents : loadTextFile(newFile(fileName), defaultContents);
}

static S loadTextFile(Reader reader) throws IOException {
  new StringBuilder builder;
  try {
    char[] buffer = new char[1024];
    int n;
    while (-1 != (n = reader.read(buffer)))
      builder.append(buffer, 0, n);
  } finally {
    reader.close();
  }
  ret str(builder);
}