Show lists with less than 2 elements and hide with more than 2

Show lists with less than 2 elements and hide with more than 2

Hey guys,

i've got a question. I would like to show childlists in a sidebar which have less than 2 elements in it, and hide childlists which have more 4 elements in it.

this is what i got til now:

$('.sf').children('li').children('ul').length <= '2'){
    $('.sf').children('li').children('ul').show();   
}

but with this code, all childlists will be shown.
i hope you'll helpin' me soon
thanks
derHINDU