Method rotate

lib/java/util/Collections.java:2047–2090

Rotates the elements in list by the distance dist e.g. for a given list with elements [1, 2, 3, 4, 5, 6, 7, 8, 9, 0], calling rotate(list, 3) or rotate(list, -7) would modify the list to look like this: [8, 9, 0, 1, 2, 3, 4, 5, 6, 7] @param lst the list whose elements

(List<?> lst, int dist)

     *            integer. Negative values rotate the list backwards.
     */
    @SuppressWarnings("unchecked")
    public static void rotate(List<?> lst, int dist) {
        List<Object> list = (List<Object>) lst;
        int size = list.size();

        // Can't sensibly rotate an empty collection
        if (size == 0) {
            return;
        }

        // normalize the distance
        int normdist;
        if (dist > 0) {
            normdist = dist % size;
        } else {
            normdist = size - ((dist % size) * (-1));
        }

        if (normdist == 0 || normdist == size) {
            return;
        }

        if (list instanceof RandomAccess) {
            // make sure each element gets juggled
            // with the element in the position it is supposed to go to
            Object temp = list.get(0);
            int index = 0, beginIndex = 0;
            for (int i = 0; i < size; i++) {
                index = (index + normdist) % size;
                temp = list.set(index, temp);
                if (index == beginIndex) {
                    index = ++beginIndex;
                    temp = list.get(beginIndex);
                }
            }
        } else {
            int divideIndex = (size - normdist) % size;
            List<Object> sublist1 = list.subList(0, divideIndex);
            List<Object> sublist2 = list.subList(divideIndex, size);
            reverse(sublist1);
            reverse(sublist2);
            reverse(list);
        }
    }

    /**
     * Searches the {@code list} for {@code sublist} and returns the beginning