实体集合中属性相同的排除

    1. public static List<User> removeDuplicate(List<User> users){
    2.     Set<User> set = new TreeSet<>(new Comparator<User>() {
    3.         @Override
    4.         public int compare(User o1, User o2) {
    5.             return  o1.getUserName().compareTo(o2.getUserName());
    6.         }
    7.     });
    8.     set.addAll(users);
    9.     return new ArrayList<User>(set);
    10. }

    实体集合的groupBy操作

    1. public static void main(String[] args){
    2.     List<TestGroup> groupList = new ArrayList<>();
    3.     TestGroup g1 = new TestGroup();
    4.     g1.setVip("精品");
    5.     g1.setOthter("test");
    6.     TestGroup g2 = new TestGroup();
    7.     g2.setVip("精品");
    8.     g2.setOthter("test2");
    9.     TestGroup g3 = new TestGroup();
    10.     g3.setVip("运营");
    11.     g3.setOthter("test2");
    12.     TestGroup g4 = new TestGroup();
    13.     g4.setVip("高级");
    14.     g4.setOthter("test2");
    15.     TestGroup g5 = new TestGroup();
    16.     g5.setVip("高级");
    17.     g5.setOthter("test2");
    18.     TestGroup g6 = new TestGroup();
    19.     g6.setVip("定制");
    20.     g6.setOthter("test2");
    21.     TestGroup g7 = new TestGroup();
    22.     g7.setVip("定制");
    23.     g7.setOthter("test2");
    24.     TestGroup g8 = new TestGroup();
    25.     g8.setVip("定制");
    26.     g8.setOthter("test2");
    27.     TestGroup g9 = new TestGroup();
    28.     g9.setVip("定制");
    29.     g9.setOthter("test2");
    31.     List<TestGroup> groups = Arrays.asList(g1,g2,g3,g4,g5,g6,g7,g8,g9);
    32.     groupList.addAll(groups);
    33.     Map<String,Long> result = groups.stream().
    34.             collect(Collectors.groupingBy(TestGroup::getVip,Collectors.counting()));
    35.     for(String s:result.keySet()){
    36.         System.out.println(s + ":" + result.get(s));
    37.     }
    38. }