List
     
       integerList = Arrays.asList(4, 5, 2, 3, 7, 9);        List
      
        collect = integerList.stream()                .map(i -> i * i).distinct()                .collect(Collectors.toList());//        Collections.sort(collect);  //升序        collect.sort(Comparator.reverseOrder()); //倒序        collect.forEach(System.out::println);