Wierd array bug

so i want to create an array with a single member of array which is variable
i call j:int;
so i do smoething like this:
var j:int = 0;
var ar:array = new array(j);
trace(ar);
and it appears as if array ar is blank =?
than i have tried some testing and found out that if i try to push it it will work just fine…
but why doesn’t it work the way it is, am I right it is a bug?