java8 lambda表达式 实现 java list 交集 并集 差集 去重复并集

javaList 交、并集采用简单的 removeAll retainAll 等操作，不过这也破坏了原始的javaList对象，采用java8 lambda表达式流操作则可以不影响原始list对象而得到两个javaList对象的 交、并、差集。
1、简单两个List<String> 交、并、差集

 /**
     * 简单类型的处理
     */
    public static void showSimpleDeal() {
        List<String> list1 = new ArrayList<>();
        list1.add("1111");
        list1.add("2222");
        list1.add("3333");

        List<String> list2 = new ArrayList<>();
        list2.add("3333");
        list2.add("4444");

        Set<String> list1Set = new HashSet<>(list1);

        Set<String> list2Set = new HashSet<>(list2);

        // 交集
        List<String> intersection = list1.stream().filter(list2Set::contains).collect(Collectors.toList());

        System.out.println("---得到交集 intersection---");
        intersection.parallelStream().forEach(System.out::println);

        // 差集 (list1 - list2)
        List<String> reduce1 = list1.stream().filter(item -> !list2Set.contains(item)).collect(Collectors.toList());

        System.out.println("---得到差集 reduce1 (list1 - list2)---");
        reduce1.parallelStream().forEach(System.out::println);

        // 差集 (list2 - list1)
        List<String> reduce2 = list2.stream().filter(item -> !list1Set.contains(item)).collect(Collectors.toList());

        System.out.println("---得到差集 reduce2 (list2 - list1)---");
        reduce2.parallelStream().forEach(System.out::println);

        // 并集
        List<String> listAll = list1.parallelStream().collect(Collectors.toList());

        List<String> listAll2 = list2.parallelStream().collect(Collectors.toList());

        listAll.addAll(listAll2);
        System.out.println("---得到并集 listAll---");
        listAll.parallelStream().forEach(System.out::println);

        // 去重并集
        list1Set.addAll(list2Set);
        List<String> listDistinctAll = new ArrayList<>(list1Set);
        System.out.println("---得到去重并集 listDistinctAll---");
        listDistinctAll.parallelStream().forEach(System.out::println);

        System.out.println("---原来的List1---");
        list1.parallelStream().forEach(System.out::println);
        System.out.println("---原来的List2---");
        list2.parallelStream().forEach(System.out::println);
    }

2、List<T> 与List<String>交、差集

static class User {
        public String name = "";
        public int age=0;

        public int getAge() {
            return age;
        }

        public void setAge(int age) {
            this.age = age;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }
    }
    public static void main(String[] args) {
        List<User> list1 = new ArrayList();
        User user1=new User();
        user1.setName("A运营");
        user1.setAge(12);
        list1.add(user1);
        User user2=new User();
        user2.setName("B运营");
        user2.setAge(22);
        list1.add(user2);
        User user3=new User();
        user3.setName("E运营");
        user3.setAge(32);
        list1.add(user3);;

       

        List<String> list2 = new ArrayList();
        list2.add("B运营");
        list2.add("C运营");
        list2.add("D运营");

        List<String> nameList= list1.stream().map(User::getName).collect(Collectors.toList());

        
        // 交集
        List<User> intersection = list1.stream().filter(item -> list2.contains(item.getName())).collect(Collectors.toList());
        System.out.println("---得到交集 intersection---");
        //intersection.parallelStream().forEach(System.out::println);
        for (User user: intersection) {
            System.out.println(user.getName());
        }

        // 差集 (list1 - list2)
        List<User> reduceUser1=list1.stream().filter(user -> !list2.contains(user.getName())).collect(Collectors.toList());
        System.out.println("---得到差集 reduce1 (list1 - list2)---");
        for (User user: reduceUser1) {
            System.out.println(user.getName());
        }
        //reduceUser1.parallelStream().forEach(System.out::println);

        // 差集 (list2 - list1)
        list1.stream().map(user -> user.getName()).collect(Collectors.toList());
        List<String> reduce2 = list2.stream().filter(item -> !nameList.contains(item)).collect(Collectors.toList());
        System.out.println("---得到差集 reduce2 (list2 - list1)---");
        reduce2.parallelStream().forEach(System.out::println);
    }

 

 

3 两个相同类型List<T> 交、并、差集

/**
     * 对象类型的处理
     */
    public static void showObjectDeal() {
        List<User> list1 = new ArrayList<>();
        list1.add(new User("name1",11));
        list1.add(new User("name2",22));
        list1.add(new User("name3",33));

        List<User> list2 = new ArrayList<>();
        list2.add(new User("name3",33));
        list2.add(new User("name4",44));

        Set<User> list1Set = new HashSet<>(list1);

        Set<User> list2Set = new HashSet<>(list2);

        // 交集
        List<User> intersection = list1.stream().filter(list2Set::contains).collect(Collectors.toList());

        System.out.println("---得到交集 intersection---");
        intersection.parallelStream().forEach(System.out::println);

        // 差集 (list1 - list2)
        List<User> reduce1 = list1.stream().filter(item -> !list2Set.contains(item)).collect(Collectors.toList());

        System.out.println("---得到差集 reduce1 (list1 - list2)---");
        reduce1.parallelStream().forEach(System.out::println);

        // 差集 (list2 - list1)
        List<User> reduce2 = list2.stream().filter(item -> !list1Set.contains(item)).collect(Collectors.toList());

        System.out.println("---得到差集 reduce2 (list2 - list1)---");
        reduce2.parallelStream().forEach(System.out::println);

        // 并集
        List<User> listAll = list1.parallelStream().collect(Collectors.toList());

        List<User> listAll2 = list2.parallelStream().collect(Collectors.toList());

        listAll.addAll(listAll2);
        System.out.println("---得到并集 listAll---");
        listAll.parallelStream().forEach(System.out::println);

        // 去重并集
        list1Set.addAll(list2Set);
        List<User> listDistinctAll = new ArrayList<>(list1Set);
        System.out.println("---得到去重并集 listDistinctAll---");
        listDistinctAll.parallelStream().forEach(System.out::println);

        System.out.println("---原来的List1---");
        list1.parallelStream().forEach(System.out::println);
        System.out.println("---原来的List2---");
        list2.parallelStream().forEach(System.out::println);
    }

4、list去重

        //List去重
        List<User> userList = list1.stream() .collect(
                Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(user -> user.getName()))), ArrayList::new));
        System.out.println("---List去重---");
        for (User user: userList) {
            System.out.println(user.getName());
        }