How does Java 8's HashMap degenerate to balanced trees when many keys have the same hash code?

Question

How does Java 8\'s HashMap degenerate to balanced trees when many keys have the same hash code? I read that keys should implement Comparable to define an order

Answer 1

Read the code. It is mostly a red-black tree.

It does not actually require the implementation of Comparable, but can use it if available (see for instance the find method)