duplicate elements

TreeSet is a Java Collections Framework class that implements the SortedSet interface. It returns a set that is sorted in natural order or by a provided comparator. TreeSet, unlike HashSet, does not allow duplicate elements and delivers fast performance for simple operations like adding, removing, and searching for elements.

HashSet is a Java Collections Framework class that implements the Set interface. It gives a collection with no duplicate elements and no set order for its elements. HashSet is built on a hash table data structure, which allows it to add, remove, and search for elements in constant time (O(1)).