Is the search time for an element in a HashMap guaranteed to be constant when using a key?

In Java's HashMap, the average time to search for an element by key is considered constant — O(1). This is achieved by using a hash function to compute the index of the bucket where the element is stored.

However, in the worst case, when all keys hash to the same bucket (due to collisions), the search can degrade to O(n), as elements in the bucket are stored as a linked list or a tree (starting from Java 8).

Thus, constant search time is only guaranteed on average, assuming a uniform distribution of hashes and no large number of collisions.