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.

The Java Collections Framework's LinkedHashSet is an implementation of the Set interface. It combines the advantages of LinkedList and HashSet. The order in which the elements were added to the set is the iteration order that the LinkedHashSet preserves. It offers constant-time performance for fundamental operations and disallows duplicate elements, just like HashSet.

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)).