java包中多个main，需要指定执行java -cp iot-device-sdk-java-0.0.5-SNAPSHOT.jar com.inspur.iot.client.sample.paho.MqttMain
https://blog.csdn.net/cold_summer_snow/article/details/79972982
https://www.cnblogs.com/gavinYang/p/11196502.html