java – Arraylist到Array转换 – toArray()函数推断类型不符合

Excel excel = new Excel();
ArrayList<Integer> a1=excel.readExcelSheet("C:UsersMadhukarDesktopEmployee.xls");
        System.out.println("Using Iterator");
        Iterator iterator = a1.iterator();
        while (iterator.hasNext()) {
       System.out.println(iterator.next());}
        int x=a1.size();
        int[] a3=new int[x];
        a3=a1.toArray(a3);

这是错误消息：

no suitable method found for toArray(int[])
method AbstractCollection.toArray(T#1[]) is not applicable
(inferred type does not conform to upper bound(s)
inferred: int
upper bound(s): Object)

06001