@Override
  public void appendLog(String log) {
    try {
      bufferedWriter.write(log);
      bufferedWriter.newLine();
      bufferedWriter.flush();
    } catch (Exception e) {
      Platform.get().warn("append log failed: " + e.getMessage());
    }
  }
Called after a log file is newly created.
<p>
You can do some initialization work to the new file, such as calling {@link #appendLog(String)}
to add a file header.
<p>
Called in worker thread.

@param file the newly created log file
xlog/src/main/java/com/elvishew/xlog/printer/file/writer/SimpleWriter.java