Sorting an ArrayList of objects using a custom sorting order

Question

I am looking to implement a sort feature for my address book application.

I want to sort an ArrayList contactArray. Contact

Answer 1

Ok, I know this was answered a long time ago... but, here's some new info:

Say the Contact class in question already has a defined natural ordering via implementing Comparable, but you want to override that ordering, say by name. Here's the modern way to do it:

List contacts = ...;

contacts.sort(Comparator.comparing(Contact::getName).reversed().thenComparing(Comparator.naturalOrder());

This way it will sort by name first (in reverse order), and then for name collisions it will fall back to the 'natural' ordering implemented by the Contact class itself.