Java 使用StringBuilder组装字符串

下面这个例子来自SpringBoot源码，这里是要打印程序启动的时间这样的字符串，需要拼装的信息有 程序名字，启动时长，JVM时长。

  private StringBuilder getStartedMessage(StopWatch stopWatch) {
    StringBuilder message = new StringBuilder();
    message.append("Started ");
    message.append(getApplicationName());
    message.append(" in ");
    message.append(stopWatch.getTotalTimeSeconds());
    try {
      double uptime = ManagementFactory.getRuntimeMXBean().getUptime() / 1000.0;
      message.append(" seconds (JVM running for " + uptime + ")");
    }
    catch (Throwable ex) {
      // No JVM time available
    }
    return message;
  }

最终拼出来的字符串效果为

Started SubscribeServerApplication in 23.103 seconds (JVM running for 27.933)