| HashSet | LinkedHashSet | TreeSet | |
| Underlying Data Structure | HashTable | HashTable and LinkedList | Balanced Tree |
| Duplicates Objects | Not Allowed | Not Allowed | Not Allowed but can be customized |
| SortingOrder | NA | NA | Applicable |
| Heterogeneous Objects | Allowed | Allowed | Not Allowed By Default |
| Null Object | Allowed | Allowed | Not Allowed |