对List中每个对象元素按时间顺序排序

import com.fengshun.patient.entity.PatMasterIndex;
import org.apache.poi.ss.usermodel.DateUtil;
import org.junit.Test;

import java.util.Collections;
import java.util.Comparator;
import java.util.Date;
import java.util.List;

import java.text.SimpleDateFormat;
import java.util.*;

public class PatMasterIndexUtil {
    public static class UserBean {
        private String id;
        private Date birthday;

        public String getId() {
            return id;
        }

        public void setId(String id) {
            this.id = id;
        }

        public Date getBirthday() {
            return birthday;
        }

        public void setBirthday(Date birthday) {
            this.birthday = birthday;
        }
    }

    public static void main(String[] args) {
        List<UserBean> list = new ArrayList<UserBean>();
        UserListGenerate(list);
        System.out.println("********排序前*******");
        for (UserBean user : list) {
            System.out.println(user.getBirthday());
        }
        ListSort(list);
        System.out.println("******排序后*****");
        for (UserBean user : list) {
            System.out.println(user.getBirthday());
        }
    }
    private static void UserListGenerate(List<UserBean> list) {
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
        try {
            Date dt1 = format.parse("1980-11-01");
            Date dt2 = format.parse("1981-12-01");
            UserBean user1 = new UserBean();
            UserBean user2 = new UserBean();
            UserBean user3 = new UserBean();
            user1.setId("zhagnsan");
            user1.setBirthday(dt1);
            user2.setId("lisi");
            user2.setBirthday(dt2);
            user3.setId("wangwu");
            list.add(user1);
            list.add(user2);
            list.add(user3);
        }catch (Exception e) {
            e.printStackTrace();
        }




    }

    private static void ListSort(List<UserBean> list) {
        Collections.sort(list, new Comparator<UserBean>() {
            @Override
            public int compare(UserBean o1, UserBean o2) {
                SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
                try {
                    Date dt1 = o1.getBirthday();
                    Date dt2 = o2.getBirthday();
                    if (dt1.getTime() > dt2.getTime()) {
                        return -1;
                    } else if (dt1.getTime() < dt2.getTime()) {
                        return 1;
                    } else {
                        return 0;
                    }
                } catch (Exception e) {
                    return 1;
                }

            }
        });
    }
}