使用stream流多字段排序SpringBoot

public class User {

    //学生id
    private Integer userId;

    //学生姓名
    private String userName;

    //学生年龄
    private Integer age;

    //学生班级
    private Integer classNo;
}

List<User> userList = new ArrayList<>();
userList.add(new User(1, "shy01", 20, 1));
userList.add(new User(2, "shy02", 18, 3));
userList.add(new User(3, "shy03", 20, 4));
userList.add(new User(4, "shy04", 19, 2));
userList.add(new User(5, "shy05", 17, 5));
userList.add(new User(6, "shy06", 16, 4));
userList.add(new User(7, "shy07", 18, 9));
userList.add(new User(8, "shy08", 19, 8));
userList.add(new User(9, "shy09", 21, 7));

userList = userList.stream().sorted(Comparator.comparing(User::getAge)).collect(Collectors.toList());
userList.forEach(System.out::println);

//方法1：先对年龄进行升序，结果进行反转
userList = userList.stream().sorted(Comparator.comparing(User::getAge).reversed()).collect(Collectors.toList());
//方法2：直接对年龄进行降序
userList = userList.stream().sorted(Comparator.comparing(User::getAge, Comparator.reverseOrder())).collect(Collectors.toList());
userList.forEach(System.out::println);

userList = userList.stream().sorted(Comparator.comparing(User::getAge).thenComparing(User::getClassNo)).collect(Collectors.toList());

//方法1：先对年龄进行升序，升序结果进行反转，再进行班级升序
userList = userList.stream().sorted(Comparator.comparing(User::getAge).reversed().thenComparing(User::getClassNo)).collect(Collectors.toList());
//方法2：直接对年龄进行降序，再对班级进行升序
userList = userList.stream().sorted(Comparator.comparing(User::getAge, Comparator.reverseOrder()).thenComparing(User::getClassNo)).collect(Collectors.toList());

//方法1：先对年龄进行升序，升序结果进行反转，再对班级进行降序
userList = userList.stream().sorted(Comparator.comparing(User::getAge).reversed().thenComparing(User::getClassNo, Comparator.reverseOrder())).collect(Collectors.toList());
//方法2：直接对年龄进行降序，再对班级进行降序
userList = userList.stream().sorted(Comparator.comparing(User::getAge, Comparator.reverseOrder()).thenComparing(User::getClassNo, Comparator.reverseOrder())).collect(Collectors.toList());
//方式3：先对年龄进行升序，再对班级进行升序，最后对结果进行反转
userList = userList.stream().sorted(Comparator.comparing(User::getAge).thenComparing(User::getClassNo).reversed()).collect(Collectors.toList());

//方法1：先对年龄进行升序，升序结果进行反转，再进行班级升序，结果进行反转(有点绕，年龄被排了三次升-降-升)
userList = userList.stream().sorted(Comparator.comparing(User::getAge).reversed().thenComparing(User::getClassNo).reversed()).collect(Collectors.toList());
//方法2：直接对年龄进行升序，再对班级进行降序
userList = userList.stream().sorted(Comparator.comparing(User::getAge).thenComparing(User::getClassNo, Comparator.reverseOrder())).collect(Collectors.toList());