Today, the HashMap docs say:
The hashes are all keyed by the thread-local random number generator on creation by default. This means that the ordering of the keys is randomized, but makes the tables more resistant to denial-of-service attacks (Hash DoS). No guarantees are made to the quality of the random data. The implementation uses the best available random data from your platform at the time of creation. This behavior can be overridden with one of the constructors.
While this is accurate, it's burying the lede: we should say much more clearly what the tradeoffs are, and point more directly toward the custom hashing infrastructure. E.g.:
By default, HashMaps use a somewhat slow hashing algorithm that provides resistance to denial-of-service attacks (Hash DoS). For cases where DoS protection isn't needed, you can opt into a faster hasher by using some details here.
Today, the HashMap docs say:
While this is accurate, it's burying the lede: we should say much more clearly what the tradeoffs are, and point more directly toward the custom hashing infrastructure. E.g.: