I also second David's approach, but even if you're sticking to your method, there's room for improvement.
The laws of logic say
(!A && !B) == !(A || B)
so this expression is shorter (because you don't need the zero comparator)
!(solobuttons[0].getValue() || solobuttons[1].getValue() || solobuttons[2].getValue() || solobuttons[3].getValue())
Programming is fun :)