public class LogService{
  private final ExecutorService  exec = new SingleThreadExecutor();
  ...
  public void start(){}

  public void stop() throws InterruptedException{
    try{
      exec.shutdown();
      exec.awaitTermination(TIMEOUT,UNIT);
    }finally{
      writer.close();
    }
  }

  public void log(String msg){
    try{
      exec.execute(new WriteTask(msg));
    }catch(RejectedExecutionException ignored){
    }
  }

}