java8中List根据某一字段去重

@Data
@AllArgsConstructor
@NoArgsConstructor
@ToString
public class User {
    private String userid;
    private String username;
    private String age;
    private String address;
   
 
}

package test;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.TreeSet;
import java.util.stream.Collectors;

public class Test1 {

    public static void main(String[] args) {
        List<User> userList = new ArrayList<>();
        
        userList.add(new User("1","李大锤","23","南京"));
        userList.add(new User("2","张无忌","18","西安"));
        userList.add(new User("3","刘德华","26","苏州"));
        userList.add(new User("4","郭靖","33","上海"));
        
        userList.add(new User("1","李大锤","23","南京"));    //id相同，其他数据也相同
        userList.add(new User("3","带头大哥","36","杭州"));  //id相同，其他数据不同
        
        System.out.println(userList);
        //根据userid去重
        userList = userList.stream().collect(Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(User :: getUserid))), ArrayList::new));
        System.out.println(userList);
    }
}

可以看出，此操作把后面的两个id相同的都给剔除了。若两个id一样，其他数据不同的话，留下的数据是靠前的数据，剔除的是靠后的数据。