private void println(int logLevel, String msg, Throwable tr) {
    if (logLevel < logConfiguration.logLevel) {
      return;
    }
    printlnInternal(logLevel, ((msg == null || msg.length() == 0)
        ? "" : (msg + SystemCompat.lineSeparator))
        + logConfiguration.throwableFormatter.format(tr));
  }
Print a log in a new line.

@param logLevel the log level of the printing log
@param msg      the message you would like to log
@param tr       a throwable object to log
xlog/src/main/java/com/elvishew/xlog/Logger.java