JEP 180: Handle Frequent HashMap Collisions with Balanced Trees

[Florian Weimer]

Opt-in via Comparable seems rather risky to me.

It's not just potential divergence between equals() and compareTo(), 
which the Comparable specification explicitly allows.  At the very 
least, you'd have to add totally separate balanced trees for each class 
of key objects.

-- 
Florian Weimer / Red Hat Product Security Team