HashSet
Basics
- Implements Set
Construction
- with predefined value (might contain duplicates)
Set<Integer> set = new HashSet<>(Arrays.asList(1,1,1,2,2,3));
Methods
| Method | Runtime | Description | Return Type |
|---|---|---|---|
| add(E e) | O(log n) | Appends the specified element to the end of this list. | boolean |
| clear() | O(n) | removes all element | void |
| contains(Object o) | O(n) worst time | contains | boolean |
| iterator() | O(1) | creates a iterator | Iterator |
| offer(E e) | O(log n) | insert element (like add) | boolean |
| peek() | O(1) | retreves the head | E |
| poll() | O(n) | retrieves and remove the head | E |
| remove(Object o) | o(n) | removes a single instance of the specified value | boolean |
| size() | O(1) | return the size | int |
| toArray()/toArray(T[] a) | O(n) | return the array | []/ T[] |