/** writes safely (to temp file, then rename) */
  public static void saveTextFile(String fileName, String contents) throws IOException {
    File file = new File(fileName);
    File parentFile = file.getParentFile();
    if (parentFile != null)
      parentFile.mkdirs();
    String tempFileName = fileName + "_temp";
    File tempFile = new File(tempFileName);
    if (contents != null) {
      if (tempFile.exists()) try {
        S saveName = tempFileName + ".saved." + now();
        copyFile(tempFile, new File(saveName));
      } catch (Throwable e) { printStackTrace(e); }
      FileOutputStream fileOutputStream = newFileOutputStream(tempFile.getPath());
      OutputStreamWriter outputStreamWriter = new OutputStreamWriter(fileOutputStream, "UTF-8");
      PrintWriter printWriter = new PrintWriter(outputStreamWriter);
      printWriter.print(contents);
      printWriter.close();
    }
    
    if (file.exists() && !file.delete())
      throw new IOException("Can't delete " + fileName);

    if (contents != null)
      if (!tempFile.renameTo(file))
        throw new IOException("Can't rename " + tempFile + " to " + file);
  }
  
  public static void saveTextFile(File fileName, String contents) {
    try {
      saveTextFile(fileName.getPath(), contents);
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }