I do not know where to place non-default Java classes so that i could be able to import them with command like this:

import myclass.myoperation;

just like

import javax.swing.JPanel;

I tried to find a proper classpath but i was not able to locate it - tired echo %CLASSPATH% and got some strange results.

thx for any help

put the jarfiles or directories on the classpaths for both your compiler and runtime and it will work fine.

Most people have a lib directory per project containing everything needed, easy to include :)