如何与 Comparator.comparing 进行比较？

Question

Hi, i want to compare and get the max date. My problem is the next one:

i got this codeline:

    Optional<User> userOptional = users.stream().max(Comparator.comparing(User::getStudent::getDate));

This is how my entites are:

User{

    Long id;
    Student student;
    ...
}

Student{
    Long id;
    Date startDate;
    ...
}

And i want to get the user with the starDate more recent.

Thanks.

Answer 1

You cannot chain two method references. Use lambda instead:

Optional<User> userOptional = users.stream().max(Comparator.comparing(user -> user.getStudent().getDate()));