//單獨String集合
        List<String> list = Arrays.asList("a","b","a","c","d","b");
        List<String> collect = list.stream().filter(i -> i != "")               // list 對應(yīng)的 Stream 并過濾""
                .collect(Collectors.toMap(e -> e, e -> 1, Integer::sum)) // 獲得元素出現(xiàn)頻率的 Map，鍵為元素，值為元素出現(xiàn)的次數(shù)
                .entrySet()
                .stream()                       // 所有 entry 對應(yīng)的 Stream
                .filter(e -> e.getValue() > 1)         // 過濾出元素出現(xiàn)次數(shù)大于 1 (重復(fù)元素）的 entry
                .map(Map.Entry::getKey)                // 獲得 entry 的鍵（重復(fù)元素）對應(yīng)的 Stream
                .collect(Collectors.toList());
        System.out.println(collect);

List<Person> personList = new ArrayList<Person>();
        personList.add(new Person("張三", 8, 3000));
        personList.add(new Person("李四", 18, 5000));
        personList.add(new Person("王五", 28, 7000));
        personList.add(new Person("孫六", 38, 9000));
        personList.add(new Person("孫六", 38, 9000));
        personList.add(new Person("孫六", 38, 10000));
       //1.先根據(jù)得到一個屬于集合 姓名
        List<String> uniqueList = personList.stream().collect(Collectors.groupingBy(Person::getName, Collectors.counting()))
                .entrySet().stream().filter(e -> e.getValue() > 1)
                .map(Map.Entry::getKey).collect(Collectors.toList());
        uniqueList.forEach(p -> System.out.println(p));
        //計算兩個list中的重復(fù)值  3條數(shù)據(jù)
        List<Person> reduce1 = personList.stream().filter(item -> uniqueList.contains(item.getName())).collect(Collectors.toList());
        System.out.println(reduce1.toString());
        //2.根據(jù)多個屬性獲取重復(fù)數(shù)據(jù)，只能重復(fù)操作得到重復(fù)的數(shù)據(jù) 工資
        List<Integer> collect1 = reduce1.stream().collect(Collectors.groupingBy(Person::getWages, Collectors.counting()))
                .entrySet().stream().filter(e -> e.getValue() > 1)
                .map(Map.Entry::getKey).collect(Collectors.toList());
        //計算兩個list中的差集
        List<Person> collect2 = reduce1.stream().filter(item -> collect1.contains(item.getWages())).collect(Collectors.toList());
        System.out.println(collect2.toString());