Generating Random Number of Circles in JavaFX

first of all, I have to say "My English is not good"

I'm trying to build a game using javaFX, just like PACMAN, but not PACMAN. I want generate some circles to generate (5-10 circles) randomly when the game starts. I know how to create circles but I don't know how to generate them randomly (I mean random number of circles, 5-10 circle).

please tell me how to do that.