Add object to ArrayList at specified index

Answer 1

How about this little while loop as a solution?

private ArrayList<Object> list = new ArrayList<Object>();

private void addObject(int i, Object object) {
    while(list.size() < i) {
        list.add(list.size(), null);
    }
    list.add(i, object);
}
....

addObject(1, object1)
addObject(3, object3)
addObject(2, object2)

Answer 2

If you are using the Android flavor of Java, might I suggest using a SparseArray. It's a more memory efficient mapping of integers to objects and easier to iterate over than a Map