I was expecting an ArrayIndexOutofBounds exception because i declared ia as a fixed array with only 4 elements (i.e. Integer ia = new Integer;) but the list contains 7 elements. It looks like even though i declared ia as being 4 elements it expanded to 7 elements as shown by the output.
Ok ill answer my own question. The API says that a new array will be created if it dont fit.
<T> T toArray(T a)
Returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array. If the list fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this list.