Please help me (how i'll see vaadin application from another computer)

Just replace localhost with the IP address of your vaadin computer. e.g. the IP address is 192.168.1.1, then access the computer remotely with the URL: http://192.168.1.1:8080/jpa-invoicer-master

Mr. Watt Lee
Thank you for your help, now i can access this page from another computer, thank you very much.
please only one help, how i'll see this page ip agents name as like 192.168.1.1 but i want to used www.ex.com

You have to buy the domain you want and register you public server at a DNS Server.
This is nothing Vaadin-specific but has to to with general internet hosting. searching for "domain", "dns", etc. should give you some good results.