Comparator sorting reported null pointer exception

        List<User> userList = new ArrayList<>();
        userList.sort(Comparator.comparing(User::getEmployeeId)) ;

When the list contains a number of empty elements Science, it will be reported null pointer exception,

Can be used

Comparator.nullsLast(String::compareTo)

Solve the problem element is empty

Results

userList.sort(Comparator.comparing(User::getEmployeeId, Comparator.nullsLast(String::compareTo)));