public static <E> Set<Set<E>> powerset(Set<E> givenSet) {
                  LinkedList<E> givenSetList = new LinkedList<E>(givenSet);
                  Set<Set<E>> powerSet = new LinkedHashSet<Set<E>>();
                  int subsetCount = (int)Math.pow(2,givenSet.size());
                  for (int i = 0; i < subsetCount; i++ ) {
                          Set<E> subSet = new LinkedHashSet<E>();
                          //System.out.println("i="+i+" ("+Integer.toBinaryString(i)+")");
                          for (E e: givenSetList) {
                                  int index = givenSetList.indexOf(e);
                                  int temp = i / (int)Math.pow(2,index);
                                  //System.out.println("temp="+temp);
  /*
                                  int temp = (i & (int)Math.pow(2,givenSetList.indexOf(e)) )
                                          % (int)Math.pow(2,givenSetList.indexOf(e));
                                                  " 2^"+
                                                  givenSetList.indexOf(e)+
                                                  "="+
                                                  (int)Math.pow(2,givenSetList.indexOf(e)));
                                                  */
                                  if ( temp % 2 == 1) {
                                          subSet.add(e);
                                  }
                          }
                          //System.out.println("one subset is "+subSet);
                          powerSet.add(subSet);
                  }
                  return powerSet;
          }