public static int[] convertIntegers(List integers)
{
    int[] ret = new int[integers.size()];
    for (int i=0; i < ret.length; i++)
    {
        ret[i] = integers.get(i).intValue();
    }
    return ret;
}

Google Guava:

List list = ...;
int[] values = Ints.toArray(list);