gistfile1.txt

    protected <T> List<List<T>> permutate(List<T> list) {
        if (list == null) {
            return null;
        } else if (list.size() == 1) {
            return Arrays.asList(list);
        } else if (list.size() == 2) {
            List<T> revList = new ArrayList<T>();
            revList.addAll(list);
            Collections.reverse(revList);
            return Arrays.asList(list, revList);
        } else {
            List<List<T>> permutations = new ArrayList<List<T>>();
            for (int i = 0; i < list.size(); i++) {
                Collections.rotate(list, 1);
                List<List<T>> permutated = permutate(list.subList(1, list.size()));
                for (List<T> p : permutated) {
                    List<T> newP = new ArrayList<T>();
                    newP.add(list.get(0));
                    newP.addAll(p);
                    permutations.add(newP);
                }
            }
            return permutations;
        }
    }