case where the port number is being used when Tomcat is started

Several ports (8005, 8080, 8009) required by Tomcat v8.0 Server at localhost are. The server may already is running in another process, or a system process may is using the port. To start this server you'll need to stop the other process or change the port number (s).
I believe that we are all familiar with this paragraph of English

This picture is also annoying. Here's the first generic solution I've summed up.
First we use the window key +r to open the Run window, in the Run window to enter CMD will pop up a black window, in the Black window input:

Netstat-ano

This is the process information that occupies three port numbers, and the last one is the system-assigned ID number 4248
Next we enter

Netstat-aon|findstr "4248"

This will list all the process IDs are 4248 information

Tasklist|findstr "4248"

Find the corresponding application

We can end the process in Task Manager.