Should a HashMap function correctly if all objects have the same hashCode value?

A HashMap in Java will function if all objects have the same hashCode value, but its efficiency will significantly decrease.

Why:

• All elements will fall into the same bucket because of the identical hashCode.
• Inside the bucket, elements are stored as a linked list or a tree (starting from Java 8 when there are many collisions).
• get/put operations will have a complexity close to O(n) instead of the expected O(1).

Thus, the HashMap will remain operational but will lose the advantage of quick access. For proper functioning and performance, it is important that hashCode distributes objects evenly across buckets.