import java.util.ArrayList;

public class AllSubsets {

    private static <T> ArrayList<ArrayList<T>> expand(ArrayList<T> tt, int ii, ArrayList<T> xpr) {
        //System.out.println("Expand on " + xpr + " " + ii);
        ArrayList<ArrayList<T>> ret = new ArrayList<>();
        if (ii >= tt.size()) {
            //System.out.println("Return []");
            //ret.add(xpr);
            return ret;
        }
        for (int j = ii; j < tt.size(); j++) {
            ArrayList<T> n = (ArrayList<T>) xpr.clone();
            n.add(tt.get(j));
            ret.addAll(expand(tt, j+1, n));
            ret.add(n);
        }
        return ret;
    }

    public static <T> ArrayList<ArrayList<T>> allSubsets(ArrayList<T> tt) {
        ArrayList<ArrayList<T>> ret = new ArrayList<>();
        for (int ii = 0; ii < (tt.size() - 0); ii++) {
            ArrayList<ArrayList<T>> tmp = new ArrayList<>();

            ArrayList<T> alt = new ArrayList<>();
            alt.add(tt.get(ii));

            tmp = expand(tt, ii + 1, alt);

            tmp.add(alt);
            System.out.println(tmp);
            ret.addAll(tmp);
        }

        return ret;
    }

    public static void main(String[] args) {
        ArrayList<Integer> gg = new ArrayList<>();
        for (int i=1; i<7; i++) 
            gg.add(i);
        
        ArrayList<ArrayList<Integer>> aass = AllSubsets.allSubsets(gg);
        System.out.println("aass" + aass);
    }
}