需求：

我们有一个对象集合，我们需要筛除那些某个字段一致的对象。这里演示去掉名字重复的对象

pojo:

    package lambda;
     
    /**
     * @author sayyes
     * @version 1.0
     * @description
     * @date 2022/7/29 09:32:15
     */
    public class User {
        private String name;
        private String address;
        private Integer age;
     
        public User() {
        }
     
     
        public User(String name, String address, Integer age) {
            this.name = name;
            this.address = address;
            this.age = age;
        }
     
        public String getName() {
            return name;
        }
     
        public void setName(String name) {
            this.name = name;
        }
     
        public String getAddress() {
            return address;
        }
     
        public void setAddress(String address) {
            this.address = address;
        }
     
        public Integer getAge() {
            return age;
        }
     
        public void setAge(Integer age) {
            this.age = age;
        }
     
        @Override
        public String toString() {
            return "User{" +
                    "name='" + name + '\'' +
                    ", address='" + address + '\'' +
                    ", age=" + age +
                    '}';
        }
    }

    package lambda;
     
    import java.util.*;
    import java.util.stream.Collectors;
     
    /**
     * @author sayyes
     * @version 1.0
     * @description
     * @date 2022/9/29 17:21:14
     */
    public class TestUserLambda {
        public static void main(String[] args) {
            User user = new User("zhangsan", "asad", 10);
            User user1 = new User("zhangsan1", "asad", 10);
            User user2 = new User("zhangsan1", "asad", 10);
            User user3 = new User("zhangsan3", "asad", 10);
            User user4 = new User("zhangsan4", "asad", 10);
            User user5 = new User("zhangsan5", "asad", 10);
            ArrayList<User> list = new ArrayList<>();
            list.add(user);
            list.add(user1);
            list.add(user2);
            list.add(user3);
            list.add(user4);
            list.add(user5);
                    List<User> collect = list.stream().collect(
                    Collectors.collectingAndThen(
                            Collectors.toCollection(
    () -> new TreeSet<>(Comparator.comparing(User::getName))), ArrayList::new));
            System.out.println(collect);
     
        }
    }

输出结果：

 方法介绍：

Collectors.collectingAndThen() 函数应该最像 map and reduce 了，它可接受两个参数，第一个参数用于 reduce操作，而第二参数用于 map操作。

也就是，先把流中的所有元素传递给第一个参数，然后把生成的集合传递给第二个参数来处理。