HashSet vs TreeSet: Understanding Ordered vs Unordered Sets in Java

The correct statement about HashSet and TreeSet is: D. HashSet is unordered, while TreeSet is ordered.

Here's why:

• HashSet: A HashSet uses a hash table to store elements. It doesn't maintain any specific order. Elements are added and retrieved based on their hash code, leading to unpredictable ordering.

• TreeSet: A TreeSet utilizes a tree data structure (specifically a red-black tree). This structure ensures elements are stored in a sorted order, typically based on the natural ordering of the elements or a custom comparator provided. This means you can access elements in ascending (or descending) order.