Is the HashCode Method for Java’s Set Really Optimal?

It's important to note that the Central Limit Theorem specifically applies to unbounded variables. In Java, we do addition modulo 2^32, meaning that even if the inputs are uniformly distributed, the sum will still be uniform after the modulo operation. Additionally, the *HashMap* uses its own spreading function for distribution, which makes the exact distribution of your hash code less crucial. Ultimately, addition is an efficient and straightforward method for generating hash codes, which is probably why it was chosen in the first place.

You're right that the current approach of summing the elements does have its drawbacks, especially in edge cases where predictable hash codes could lead to collisions. However, the design decision also aims to keep the hash codes consistent across different implementations. Even though using XOR or other fancy hashing techniques could be considered, the simplicity of summing elements likely played a big role in this decision. Plus, it keeps things orderly since sets are unordered.

I think there’s a misunderstanding about what makes a good hash function. The sum does indeed produce a uniform distribution for hash maps, but fast performance is also a key consideration. So while a more complex hash code may seem optimal in theory, it’s often not worth the trading down in performance and simplicity. Using a set as a key in a hash map also poses challenges, especially since the set must be immutable; that complicates things further. Overall, maintaining a consistent hash code across different frameworks must have weighed heavily in their decision.