Geoffrey De Smet Geoffrey De Smet - 2 months ago 6x
Java Question

Comparator.comparing(...) of a nested field

Suppose I have a domain model like this:

class Lecture {
Course course;
... // getters

class Course {
Teacher teacher;
int studentSize;
... // getters

class Teacher {
int age;
... // getters

Now I can create a Teacher Comparator like this:

return Comparator

But how do I compare Lecture's on nested fields, like this?

return Comparator

I can't add a method
on the model.


You can't nest method references. You can use lambda expressions instead :

return Comparator
        .comparing(l->l.getCourse().getTeacher().getAge(), Comparator.reverseOrder())