What is the time complexity of searching for an element in a HashMap in the worst-case scenario?

In the worst-case scenario, the time complexity of searching for an element in a HashMap in Java can be O(n), where n is the number of elements in the map. This occurs when all elements hash to the same bucket, and the data structure within the bucket degrades to a linked list. However, starting with Java 8, when there are many collisions, the linked list is converted into a balanced tree (TreeNode), which improves the worst case to O(log n).