How I Would Re-design equals()

I want to rant a bit about Java design, in particular about the methods Object.equals() and Comparable.compareTo(). I've hated them for years, because, no matter how hard I try to like them, the code inside looks ugly. Now I know what exactly is wrong and how I would design this "object-to-object comparing" mechanism better.

[image error]L'ultimo capodanno (1998) by Marco Risi

Say we have a simple primitive class Weight, objects of which represent the weight of something in kilos:

class...