Question

I want to sort Collection of Objects, which does not implement comparable or comparater interface. The problem is I cannot change the class design because I have only .class(no source code) file. How can I achive this?

Answer 1

You can sort by providing a custom Comparator. You don’t need to implement Comparable.

See Collections.sort(List s, Comparator c) and the Collections ordering tutorial – specifically the section labelled Comparators:

What if you want to sort some objects in an order other than their
natural ordering? Or what if you want to sort some objects that don’t
implement Comparable?