What is the difference between `HashSet` and `TreeSet`?

The main differences between HashSet and TreeSet lie in their internal implementation and ordering:

• HashSet:
  • Does not maintain any order of elements.
  • Uses a hash table for storing elements.
  • Faster operations for add, remove, and contains (O(1) average time complexity).
• TreeSet:
  • Maintains elements in a sorted order (natural or according to a comparator).
  • Uses a Red-Black tree for storing elements.
  • Slower operations compared to HashSet (O(log n) for add, remove, and contains) due to the sorting.

In summary, use HashSet for unordered collections with fast operations and TreeSet for sorted collections with a higher time complexity for operations.