利用java怎么对集合的子集进行求解

@Test public void test1() throws Exception {      Set<ArrayList<Integer>> subsets = getSubsets( Arrays.asList(1,2,6));   Set<ArrayList<String>> subsets2 = getSubsets( Arrays.asList("a","b","c"));   Set<ArrayList<Character>> subsets3 = getSubsets( Arrays.asList('b','c','d'));   System.out.println(subsets);   System.out.println(subsets2);   System.out.println(subsets3); }  //集合接受各种类型数据 public <T> Set<ArrayList<T>> getSubsets(List<T> subList) {   //考虑去重   Set<ArrayList<T>> allsubsets = new LinkedHashSet<>();   int max = 1 << subList.size();   for (int loop = 0; loop < max; loop++) {     int index = 0;     int temp = loop;     ArrayList <T> currentCharList = new ArrayList<T>();     //控制索引     while (temp > 0) {       if ((temp & 1) > 0) {         currentCharList.add(subList.get(index));       }       temp >>= 1;       index++;     }     allsubsets.add(currentCharList);   }   return allsubsets; }