Tomcat启动报错Port 8080 required by Tomcat v9.0 Server at localhost is already in use. The server may already be running in another process, or a system process may be using the port.

完整报错信息：

Port 8080 required by Tomcat v9.0 Server at localhost is already in use. The server may already be running in another process, or a system process may be using the port. To start this server you will need to stop the other process or change the port.
主要原因是你之间运用过程中占用了端口，只需要找到该端口结束其进程即可。

（1）打开cmd（win+R），输入netstat -ano|findstr 8080

 

 找到8080端口号对应的PID码，如6536

（2）打开资源管理器(Ctrl+Alt+Del)-详细信息，找到PID码为6536的进程，结束进程树

 

 重启系统，再次打开tomcat即可