code: public synchronized void log(@Nullable Level level, @Nullable String msg, @Nullable Throwable t) {
          if (!isLoggable(level))
              return;
          System.err.println(df.format(new Date()) + " [" + Thread.currentThread().getName() + "] " + name + " - " + level.getName() + ": " + msg);
          if (t != null)
              t.printStackTrace();
  
      }
docs: synchronize for the {@link java.text.SimpleDateFormat}.
  
  @param level
  @param msg
  @param t