Validating a JOptionPane ConfirmDialog
Your approach seems fine. But some minor improvements are possible:


It's unnatural to write !(x == y), the more natural way is x != y
I'm wondering if option is needed outside the loop are all. If not, then you should declare and initialize it inside the loop. 
in every iteration, you check cboFruits.getSelectedItem()== null twice: once after the use clicked OK, and then again in the loop condition. It would be better to rearrange this code in a way that the condition is checked once per iteration.
It's recommended to use braces always, even with single line if statements