Runtime
| Set | add | remove | contains | next | size | Data Structure |
|---|---|---|---|---|---|---|
| HashSet | O(1) | O(1) | O(1) | O(h/n) | O(1) | Hash Table |
| LinkedHashSet | O(1) | O(1) | O(1) | O(1) | O(1) | Hash Table + Linked List |
| EnumSet | O(1) | O(1) | O(1) | O(1) | O(1) | Bit Vector |
| TreeSet | O(log n) | O(log n) | O(log n) | O(log n) | O(1) | Red-black tree |
| CopyOnWriteArraySet | O(n) | O(n) | O(n) | O(1) | O(1) | Array |
| ConcurrentSkipListSet | O(log n) | O(log n) | O(log n) | O(1) | O(n) | Skip List |