Is there any way to make this work in Java?

public static void change(List<? extends Object> list, int position1, int position2) {
    Object obj = list.get(position1);
    list.set(position1, list.get(position2));
    list.set(position2, obj);
}

The only way I've successfully avoided warnings and errors is this:

public static <T> T change(List<T> list, int position1, int position2) {
    T obj = list.get(position1);
    list.set(position1, list.get(position2));
    list.set(position2, obj);
    return obj;
}

but I don't like to be forced to return a value.