MySQL installation may shared between (locally servers localhost) Tomcat/JSP/Java and Apache/PHP? I mean having both server but one MySQL ...? May same time operate both servers and MySQL serves both same time?

a MySQL server can serve data to as many clients as needed, whether they be web servers or workstations.. its immaterial.

by saying "clients" you mean Web Servers(in case locally) ? either these run same time or at differ time each?

a, any, db server exists to serve clients requesting data
as far as the db server is concerned, it doesn't matter if the clients requesting data are web servers, access applications on user desktops, embedded systems, bespoke software developed in Java, C, .NET. providign the server and the netwrok infrastructure is up to it a server serves data.

Clients = one connection to MySQL.

If your Tomcat makes one connection to MySQL, it's one client.

Then at the same time (or not at the same time), you have PHP/Apache connects to the same MySQL server, then it's the second client.

Then you may also have other clients, like SQLyog connecting to MySQL ... it's also (you guessed it) a client.

Also, you may have PDNS running and connecting to the same MySQL. Needless to say, it's also another client.

As far as MySQL concerns, it doesn't care if Tomcat/Java or PHP/Apache or SQLyog or PDNS or any other software you can imagine connects to it (as long as the credentials checks). It just count how many connections are open at any given time. If something is connecting to it, it'll check the credentials and check if it can still make connections. If yes, then you're in. If not, then MySQL will throw too many connection erros.