How to call functions from toolkit written in Java?

I have some problems with building java toolbox. I try to call sum(a, b) function from the example. I wrote

exec("myPath\builder_java.sce")
exec("myPath\loader.sce")

And I see jar file that was created. But when I write y = sum(1, 2) scilab generates error 4: Undefined variable: sum. So, how should I call this function?